vendex and Pain

The purpose of this study is to investigate the relationships between subjective measures of discomfort and objective measures related to the assessment of postural stresses based on literature survey. Objective measures included posture holding time, maximum holding time (MHT), torque at joints, lifting index (LI) and compressive force (CF) at L5/S1. The major relationships identified in this literature survey were the following: 1) postural discomfort linearly increased with increasing holding time, and holding force, 2) whole body discomfort was inversely linearly proportional to the MHT, 3) body-part discomfort was related to objective measures such as torque at the relevant joint, 4) discomfort was strongly linearly related to LIs and CFs, and 5) the discomfort measured with the magnitude estimation was linearly related to that measured with Borg CR10. Thus, it is thought that discomfort might be used as a measure for quantifying postural stresses.

Topics: Ergonomics; Humans; Male; Musculoskeletal Diseases; Pain; Posture; Torque; Weight-Bearing

Exercise-induced muscle damage (EIMD) is prevalent especially in sports and rehabilitation. It causes loss in skeletal muscle function and soreness. As there are no firm preventive strategies, we aimed to evaluate the preventive efficacy of nonthermal 448-kHz capacitive resistive monopolar radiofrequency (CRMRF) therapy after eccentric bouts of EIMD response in knee flexors.. Twenty-nine healthy males (age: 25.2 [4.6] y) were randomized in control group (CG; n = 15) and experimental group (EG; n = 14) where EG followed 5 daily 448-kHz CRMRF therapies. All assessments were performed at baseline and post EIMD (EIMD + 1, EIMD + 2, EIMD + 5, and EIMD + 9 d). We measured tensiomyography of biceps femoris and semitendinosus to calculate contraction time, the maximal displacement and the radial velocity of contraction, unilateral isometric knee flexors maximal voluntary contraction torque, and rate of torque development in first 100 milliseconds.. Maximal voluntary contraction torque and rate of torque development in first 100 milliseconds decreased more in CG than in EG and recovered only in EG. Biceps femoris contraction time increased only in CG (without recovery), whereas in semitendinosus contraction time increased in EG (only at EIMD + 1) and in CG (without recovery). In both muscles, tensiomyographic maximal displacement decreased in EG (in EIMD + 1 and EIMD + 2) and in CG (without recovery). Furthermore, in both muscles, radial velocity of contraction decreased in EG (from EIMD + 1 until EIMD + 5) and in CG (without recovery).. The study shows beneficial effect of CRMRF therapy after inducing EIMD in skeletal muscle strength and contractile parameters in knee flexors.

Topics: Adult; Humans; Isometric Contraction; Male; Muscle Contraction; Muscle Strength; Muscle, Skeletal; Myalgia; Pain; Torque

Athletes such as long-distance runners, sprinters, hockey, and/or football players may have proximal hamstring tendinopathy (PHT). Laser therapy has been shown to be effective in tendinopathies. High power laser therapy (HPLT) is used for the treatment of several musculoskeletal conditions; however, its efficacy on PHT has not been investigated. This study is aimed at examining the effects of HPLT on pain and isokinetic peak torque (IPT) in athletes with PHT. The two-arm comparative pretest-posttest experimental design was used with random allocation of 36 athletes aged 18-35 years into two groups (experimental and conventional group). The experimental group included the application of HPLT for 3 weeks. The conventional group included treatment with a conventional physiotherapy program including ultrasound therapy, moist heat pack, and home exercises for a total of 3 weeks. Pain and IPT of the hamstring muscle were measured before and after the application of the intervention. Pain score decreased, and IPT increased significantly (

Topics: Athletes; Hamstring Muscles; Humans; Laser Therapy; Pain; Tendinopathy; Torque

Wong, V, Dankel, SJ, Spitz, RW, Bell, ZW, Viana, RB, Chatakondi, RN, Abe, T, and Loenneke, JP. The effect of blood flow restriction therapy on recovery after experimentally induced muscle weakness and pain. J Strength Cond Res 36(4): 1147-1152, 2022-The purpose was to determine if blood flow restriction with no external load could be used as a means of active therapy after experimentally induced fatigue and soreness. Twelve women and 7 men (aged 18-35 years) participated in a randomized controlled trial using a within-subject design. The study intervention was 3 consecutive visits. Visit 1 included the fatiguing/soreness-inducing protocol for the elbow flexors, which was performed only once during the study. Torque was measured before/after to confirm individuals began in a weakened state. Subjects then completed blood flow restriction therapy on one arm and the sham therapy on the other. Subjects performed elbow flexion/contraction with no external load on both arms. Torque was measured once more 10 minutes after the fatiguing/soreness-inducing protocol. Twenty-four hours later, soreness and torque were assessed in each arm, followed by another bout of therapy. Forty-eight hours after the initial visit, soreness and torque were measured again. There were no differences (median difference [95% credible interval]) in the recovery of torque between the blood flow restriction and sham therapy conditions at 10 minutes (0.5 [-2.7, 3.8] N·m), 24 hours (-2.34 [-6, 1.14] N·m), or 48 hours (-1.94 [-5.45, 1.33] N·m). There were also no differences in ratings of soreness at 24 hours (-2.48 [-10.05, 5.05]) or 48 hours (2.58 [-4.96, 10.09]). Our results indicate that this specific model of blood flow restriction therapy did not enhance the recovery of the muscle compared with a sham condition without the application of pressure.

Topics: Adolescent; Adult; Blood Flow Restriction Therapy; Exercise; Female; Humans; Male; Muscle Weakness; Muscle, Skeletal; Pain; Torque; Young Adult

To compare the effectiveness of adding anteromedial versus posterolateral hip musculature strengthening to knee strengthening in women with patellofemoral pain (PFP).. Randomized controlled trial.. University physiotherapy clinic.. Fifty-two women with PFP were randomized to receive either anteromedial (AMHG) or posterolateral (PLHG) hip musculature strengthening.. The primary outcomes were pain intensity by the numeric pain rating scale and function by the Anterior Knee Pain Scale in six weeks. Secondary outcomes were pain and function at six months, global perceived effect at six weeks and six months, pain in step down, isometric torque of abductors, adductors and hip rotators measured with hand-held dynamometer, and dynamic knee valgus by step down in six weeks.. Both groups showed improvement in primary outcomes; however, no differences were found between groups in pain intensity and function in six weeks and the secondary outcomes. Group x time interaction found superior gains in abductor strength in the PLHG and increase in the strength of the adductors and internal rotators in AMHG.. There was no difference between the addition of anteromedial or posterolateral hip musculature strengthening to knee strengthening in improving pain and function in women with PFP.

Topics: Adult; Exercise Therapy; Female; Hip; Humans; Knee; Muscle Strength; Muscle Strength Dynamometer; Muscle, Skeletal; Pain; Pain Measurement; Patellofemoral Pain Syndrome; Torque

We implemented a blood flow restriction resistance training (BFR-RT) intervention during an 8-week rehabilitation programme in anterior cruciate ligament reconstruction (ACLR) patients within a National Health Service setting.. To compare the effectiveness of BFR-RT and standard-care traditional heavy-load resistance training (HL-RT) at improving skeletal muscle hypertrophy and strength, physical function, pain and effusion in ACLR patients following surgery.. 28 patients scheduled for unilateral ACLR surgery with hamstring autograft were recruited for this parallel-group, two-arm, single-assessor blinded, randomised clinical trial following appropriate power analysis. Following surgery, a criteria-driven approach to rehabilitation was utilised and participants were block randomised to either HL-RT at 70% repetition maximum (1RM) (n = 14) or BFR-RT (n = 14) at 30% 1RM. Participants completed 8 weeks of biweekly unilateral leg press training on both limbs, totalling 16 sessions, alongside standard hospital rehabilitation. Resistance exercise protocols were designed consistent with standard recommended protocols for each type of exercise. Scaled maximal isotonic strength (10RM), muscle morphology of the vastus lateralis of the injured limb, self-reported function, Y-balance test performance and knee joint pain, effusion and range of motion (ROM) were assessed at pre-surgery, post-surgery, mid-training and post-training. Knee joint laxity and scaled maximal isokinetic knee extension and flexion strength at 60°/s, 150°/s and 300°/s were measured at pre-surgery and post-training.. Four participants were lost, with 24 participants completing the study (12 per group). There were no adverse events or differences between groups for any baseline anthropometric variable or pre- to post-surgery change in any outcome measure. Scaled 10RM strength significantly increased in the injured limb (104 ± 30% and 106 ± 43%) and non-injured limb (33 ± 13% and 39 ± 17%) with BFR-RT and HL-RT, respectively, with no group differences. Significant increases in knee extension and flexion peak torque were observed at all speeds in the non-injured limb with no group differences. Significantly greater attenuation of knee extensor peak torque loss at 150°/s and 300°/s and knee flexor torque loss at all speeds was observed with BFR-RT. No group differences in knee extensor peak torque loss were found at 60°/s. Significant and comparable increases in muscle thickness (5.8 ± 0.2% and 6.7 ± 0.3%) and pennation angle (4.1 ± 0.3% and 3.4 ± 0.1%) were observed with BFR-RT and HL-RT, respectively, with no group differences. No significant changes in fascicle length were observed. Significantly greater and clinically important increases in several measures of self-reported function (50-218 ± 48% vs. 35-152 ± 56%), Y-balance performance (18-59 ± 22% vs. 18-33 ± 19%), ROM (78 ± 22% vs. 48 ± 13%) and reductions in knee joint pain (67 ± 15% vs. 39 ± 12%) and effusion (6 ± 2% vs. 2 ± 2%) were observed with BFR-RT compared to HL-RT, respectively.. BFR-RT can improve skeletal muscle hypertrophy and strength to a similar extent to HL-RT with a greater reduction in knee joint pain and effusion, leading to greater overall improvements in physical function. Therefore, BFR-RT may be more appropriate for early rehabilitation in ACLR patient populations within the National Health Service.

Topics: Adult; Anterior Cruciate Ligament Injuries; Anterior Cruciate Ligament Reconstruction; Constriction; Female; Hamstring Muscles; Humans; Male; Muscle Strength; Pain; Pain Management; Quadriceps Muscle; Range of Motion, Articular; Regional Blood Flow; Resistance Training; Single-Blind Method; State Medicine; Torque; United Kingdom; Young Adult

The benefits of neuromuscular electrical stimulation (NMES) for rehabilitation depend on the capacity to generate functionally relevant torque with minimal fatigability and discomfort. Traditionally, NMES is delivered either over a muscle belly (mNMES) or a nerve trunk (nNMES). Recently, a technique that minimizes contraction fatigability by alternating pulses between the mNMES and nNMES sites, termed "interleaved" NMES (iNMES), was developed. However, discomfort and the ability to generate large torque during iNMES have not been explored adequately.. The study objective was to compare discomfort and maximal torque between mNMES, nNMES, and iNMES.. Stimulation trains (12 pulses at 40 Hz) were delivered to produce dorsiflexion torque using mNMES, nNMES, and iNMES. Discomfort was assessed using a visual analogue scale for contractions that generated 5-30% of a maximal voluntary isometric contraction (MVIC), and for the maximal tolerable torque.. Discomfort scores were not different between NMES types when torque was ≤20% MVIC. At 30% MVIC, mNMES produced more discomfort than nNMES and iNMES. nNMES produced the most torque (65% MVIC), followed by iNMES (49% MVIC) and mNMES (33% MVIC); in these trials, mNMES produced more discomfort than nNMES, but not iNMES.. The present results may be limited to individuals with no history of neuromusculoskeletal impairment.. In terms of discomfort, there were no differences between mNMES, nNMES, or iNMES for contractions between 5-20% MVIC. However, mNMES produced more discomfort than nNMES and iNMES for contractions of 30% MVIC, while for larger contractions, mNMES only produced more discomfort than nNMES. The advantages and disadvantages of each NMES type should be considered prior to implementation in rehabilitation programs.

Topics: Adult; Ankle Joint; Electric Stimulation Therapy; Female; Humans; Isometric Contraction; Male; Muscle, Skeletal; Pain; Range of Motion, Articular; Torque; Young Adult

The purpose of this study was to determine optimal stimulation parameters and calculation methods to estimate quadriceps voluntary activation while minimizing participant discomfort. Twelve healthy adults (8 men and 4 women; mean ± SD, age = 36.8 ± 15.6 years, weight = 76.1 ± 12.9 kg, height = 170.2 ± 8.6 cm). Repeated maximal volitional isometric contractions (MVIC) were performed while imposing 4 stimulation combinations (10 or 2 pulses; 400 or 200 V; and variable or standardized current) with the quadriceps in a relaxed state (resting twitch [RT]) and during an MVIC. Quadriceps activation was quantified by calculating the central activation ratio and the percent activation. Discomfort was quantified using the visual analog scale. When comparing calculation methods between the same stimulation parameters, the central activation ratio calculation method produced quadriceps activation values that were significantly greater (p < 0.009) than those derived using the percent activation calculation method. The doublet pulse stimulus produced less discomfort during the RT (p < 0.04) and MVIC (p < 0.001) when compared with all other combinations using a train of stimuli (10 pulses). Correlations for all estimates of quadriceps activation were strong (r = 0.85-0.99, p < 0.001). A doublet pulse stimulus produced discomfort levels that were over 50% lower than a 10-pulse train of stimuli and correlated well (r > 0.88) with activation levels obtained with a 10-pulse train of stimuli. Therefore, the use of a doublet pulse stimulus provides quadriceps activation information equivalent to other methods while minimizing participant discomfort.

Topics: Adult; Cross-Over Studies; Electric Stimulation; Female; Humans; Isometric Contraction; Male; Mathematical Concepts; Middle Aged; Pain; Pain Measurement; Quadriceps Muscle; Torque; Young Adult

This study investigated the effects of knee localised muscle damage on running kinematics at varying speeds. Nineteen young women (23.2 ± 2.8 years; 164 ± 8 cm; 53.6 ± 5.4 kg), performed a maximal eccentric muscle damage protocol (5 × 15) of the knee extensors and flexors of both legs at 60 rad · s(-1). Lower body kinematics was assessed during level running on a treadmill at three speeds pre- and 48 h after. Evaluated muscle damage indices included isometric torque, muscle soreness and serum creatine kinase activity. The results revealed that all indices changed significantly after exercise, indicating muscle injury. Step length decreased and stride frequency significantly increased 48 h post-exercise only at the fastest running speed (3 m · s(-1)). Support time and knee flexion at toe-off increased only at the preferred transition speed and 2.5 m · s(-1). Knee flexion at foot contact, pelvic tilt and obliquity significantly increased, whereas hip extension during stance-phase, knee flexion during swing-phase, as well as knee and ankle joints range of motion significantly decreased 48 h post-exercise at all speeds. In conclusion, the effects of eccentric exercise of both knee extensors and flexors on particular tempo-spatial parameters and knee kinematics of running are speed-dependent. However, several pelvic and lower joint kinematics present similar behaviour at the three running speeds examined. These findings provide new insights into how running kinematics at different speeds are adapted to compensate for the impaired function of the knee musculature following muscle damage.

Topics: Adult; Biomechanical Phenomena; Creatine Kinase; Exercise; Female; Gait; Humans; Knee; Knee Joint; Leg; Muscle Contraction; Muscle, Skeletal; Pain; Pelvis; Range of Motion, Articular; Running; Task Performance and Analysis; Torque; Young Adult

This study investigated whether low-intensity eccentric contractions of the knee extensors would attenuate the magnitude of muscle damage induced by maximal eccentric exercise of the same muscle performed 7 days later using elderly individuals. Healthy older men (66.4 ± 4.6 years) were assigned to control or experimental (Exp) group (n = 13 per group). The control group performed six sets of ten maximal eccentric contractions (MaxECC) of the knee extensors of non-dominant leg. The Exp group performed six sets of ten low-intensity eccentric contractions of the knee extensors on a leg extension machine by lowering a weight of 10 % maximal voluntary isometric knee extension strength (10 %ECC) 7 days prior to MaxECC. Changes in maximal voluntary isokinetic concentric torque (MVC-CON), angle at peak torque, range of motion (ROM), upper thigh circumference, muscle soreness, plasma creatine kinase activity and myoglobin (Mb) concentration and B-mode ultrasound echo-intensity before and for 5 days after MaxECC were compared between groups by a mixed factor ANOVA. No significant changes in any variables were observed following 10 %ECC. Following MaxECC, all variables changed significantly, and changes in all variables except for angle at peak torque were significantly different between groups. MVC-CON and ROM decreased smaller and recovered faster (P < 0.05) for Exp than control group, and changes in other variables were smaller (P < 0.05) for Exp group compared with control group. These results suggest that preconditioning knee extensor muscles with low-intensity eccentric contractions was effective for attenuating muscle damage induced by subsequent MaxECC of the knee extensors for elderly individuals.

Topics: Age Factors; Aged; Analysis of Variance; Biomarkers; Biomechanical Phenomena; Creatine Kinase; Exercise; Exercise Therapy; Humans; Isometric Contraction; Male; Middle Aged; Muscle, Skeletal; Muscular Diseases; Myoglobin; Pain; Range of Motion, Articular; Taiwan; Time Factors; Torque; Ultrasonography; Volition

This study examined the effects of short-term eccentric-concentric knee extensor training on mechanical and biochemical variables, myoelectric activity, and muscle soreness. Seventeen men were assigned to either experimental (E, n = 10) or control group (C, n = 7). Group E performed 90 maximal isokinetic eccentric-concentric knee extensor contractions on each of 3 consecutive days (Tr1-Tr3) followed by 1-day rest, and then on 4 more consecutive days (Tr4-Tr7). Peak eccentric torque of each contraction during the training was recorded and averaged for each session (MTr). Maximal isometric torque (M0), eccentric torque (M(ecc)), integrated electromyography (iEMG), plasma creatine kinase (CK), and lactate dehydrogenase (LDH) activities were measured before, immediately, 24, 48, and 72 hours after Tr1, at 1 and 3 days after Tr7. Group C did not train but performed all exercise tests; CK and LDH were measured at 3 time points only. Acutely, M0 and M(ecc) decreased and CK, LDH, and soreness increased more in E than in C 24 hours after Tr1. Chronically, MTr and M0 increased more in E than C by Tr7 and CK, LDH, and muscle soreness gradually decreased by Tr7 whereas iEMG increased more in E than in C after Tr3 through Tr7. High-intensity short-term eccentric-concentric knee extensor exercise training produced immediate reductions in maximal voluntary force. Most likely neural adaptations contributed to rapid recovery and strength adaptations because maximal voluntary force increased by the end of the training protocol in previously trained healthy adults.

Topics: Adolescent; Adult; Creatine Kinase; Electromyography; Exercise; Humans; Knee; Male; Muscle Contraction; Muscle, Skeletal; Pain; Torque; Young Adult

This study examined the effects of cold therapy (COLD) on recovery of voluntary and evoked contractile properties following high-intensity, muscle-damaging and fatiguing exercise. Ten resistance-trained males performed 6 × 25 maximal concentric/eccentric muscle contractions of the dominant knee extensors (KE) followed by a 20-min recovery (COLD v control) in a randomized cross-over design. Voluntary and evoked neuromuscular properties of the right KE, ratings of perceived muscle soreness (MS) and pain, and blood markers for muscle damage were measured pre- and post-exercise, and immediately post-recovery, 2, 24 and 48-h post-recovery. Exercise resulted in decrements in voluntary and evoked torque, increased MS and elevated muscle damage markers (p < 0.05). Measures of maximal voluntary contraction (MVC) or voluntary activation (VA) were not significantly enhanced by COLD (p > 0.05). Activation of right KE decreased post-exercise with increased activation of biceps femoris (BF) (p < 0.05). However, no significant differences were evident between conditions of activation of KE and hamstrings at any time point (p > 0.05). No significant differences were observed between conditions for creatine kinase or asparate aminotransferase (p > 0.05). However, perceptual ratings of pain were significantly (p < 0.05) lower following COLD compared to control. In conclusion, following damage to the contractile apparatus, COLD did not significantly hasten the recovery of peripheral contractile trauma. Despite no beneficial effect of COLD on recovery of MVC, perceptions of pain were reduced following COLD.

Topics: Adult; Aspartate Aminotransferases; Biomarkers; Creatine Kinase; Cross-Over Studies; Cryotherapy; Electromyography; Exercise; Humans; Knee; Knee Joint; Male; Muscle Contraction; Muscle Fatigue; Muscle, Skeletal; Pain; Physical Exertion; Recovery of Function; Resistance Training; Torque; Young Adult

Muscle pain has widespread effects on motor performance, but the effect of pain on voluntary activation, which is the level of neural drive to contracting muscle, is not known. To determine whether induced muscle pain reduces voluntary activation during maximal voluntary contractions, voluntary activation of elbow flexors was assessed with both motor-point stimulation and transcranial magnetic stimulation over the motor cortex. In addition, we performed a psychophysical experiment to investigate the effect of induced muscle pain across a wide range of submaximal efforts (5-75% maximum). In all studies, elbow flexion torque was recorded before, during, and after experimental muscle pain by injection of 1 ml of 5% hypertonic saline into biceps. Injection of hypertonic saline evoked deep pain in the muscle (pain rating ∼5 on a scale from 0 to 10). Experimental muscle pain caused a small (∼5%) but significant reduction of maximal voluntary torque in the motor-point and motor cortical studies (P < 0.001 and P = 0.045, respectively; n = 7). By contrast, experimental muscle pain had no significant effect on voluntary activation when assessed with motor-point and motor cortical stimulation although voluntary activation tested with motor-point stimulation was reduced by ∼2% in contractions after pain had resolved (P = 0.003). Furthermore, induced muscle pain had no significant effect on torque output during submaximal efforts (P > 0.05; n = 6), which suggests that muscle pain did not alter the relationship between the sense of effort and production of voluntary torque. Hence, the present study suggests that transient experimental muscle pain in biceps brachii has a limited effect on central motor pathways.

Topics: Adult; Analysis of Variance; Biomechanical Phenomena; Brachial Plexus; Electric Stimulation; Electromyography; Female; Humans; Injections, Intramuscular; Linear Models; Male; Middle Aged; Motor Cortex; Muscle Contraction; Muscle, Skeletal; Neural Pathways; Pain; Pain Measurement; Saline Solution, Hypertonic; Torque; Transcranial Magnetic Stimulation; Upper Extremity; Volition; Young Adult

Exercise-induced muscle damage (EIMD) leads to decrements in muscle performance and increases in intramuscular enzymes measured in the plasma, and to delayed onset of muscle soreness (DOMS), partly due to the activation of degradative pathways. It has been shown that milk-based carbohydrate-protein (CHO-P) can limit changes in markers of EIMD, possibly by attenuating protein degradation and (or) increasing protein synthesis. However, the timing of supplementation has received limited attention, and this may alter the response. This study examined the effects of acute milk-based CHO-P supplementation timing on the attenuation of EIMD. Four independent matched groups of 8 healthy males consumed milk-based CHO-P before (PRE), immediately after (POST), or 24 h after (TWENTY-FOUR) muscle-damaging exercise. Active DOMS, isokinetic muscle performance, reactive strength index (RSI), and creatine kinase (CK) were assessed immediately before and 24, 48, and 72 h after EIMD. POST and TWENTY-FOUR demonstrated a benefit in limiting changes in active DOMS, peak torque, and RSI over 48 h, compared with PRE. PRE showed a possible benefit in reducing increases in CK over 48 h and limiting changes in other variables over 72 h. Consuming milk-based CHO-P after muscle-damaging exercise is more beneficial in attenuating decreases in muscle performance and increases in active DOMS at 48 h than ingestion prior to exercise.

Topics: Administration, Oral; Animals; Beverages; Biomarkers; Creatine Kinase, MM Form; Dietary Carbohydrates; Dietary Supplements; Drug Administration Schedule; Exercise; Humans; Male; Milk Proteins; Muscle Contraction; Muscle Strength; Muscle Strength Dynamometer; Muscle, Skeletal; Muscular Diseases; Pain; Pain Measurement; Recovery of Function; Single-Blind Method; Time Factors; Torque

This study compared alternating current and pulsed current electrical muscle stimulation (EMS) for torque output, skin temperature (Tsk), blood lactate and hormonal responses, and skeletal muscle damage markers. Twelve healthy men (23-48 yr) received alternating current EMS (2.5 kHz delivered at 75 Hz, 400 micros) for the knee extensors of one leg and pulsed current (75 Hz, 400 micros) for the other leg to induce 40 isometric contractions (on-off ratio 5-15 s) at the knee joint angle of 100 degrees (0 degrees: full extension). The use of the legs for each condition was counterbalanced among subjects, and the two EMS bouts were separated by 2 wk. The current amplitude was consistently increased to maximally tolerable level, and the torque and perceived intensity were recorded over 40 isometric contractions. Tsk of the stimulated and contralateral knee extensors were measured before, during, and for 30 min after EMS. Blood lactate, growth hormone, testosterone, insulin-like growth factor 1, testosterone, and cortisol were measured before, during, and for 45 min following EMS. Muscle damage markers included maximal voluntary isometric contraction torque, muscle soreness with a 100-mm visual analog scale, and plasma creatine kinase (CK) activity, which were measured before and 1, 24, 48, 72, and 96 h after EMS. No significant differences in the torque induced during stimulation (approximately 30% maximal voluntary isometric contraction) and perceived intensity were found, and changes in Tsk, blood lactate, and hormones were not significantly different between conditions. However, all of the measures showed significant (P<0.05) changes from baseline values. Skeletal muscle damage was evidenced by prolonged strength loss, development of muscle soreness, and increases in plasma CK activity; however, the changes in the variables were not significantly different between conditions. It is concluded that acute effects of alternating and pulsed current EMS on the stimulated muscles are similar.

Topics: Adult; Biomarkers; Electric Stimulation; Hormones; Humans; Isometric Contraction; Knee; Lactic Acid; Male; Middle Aged; Muscle Strength; Muscle, Skeletal; Pain; Pain Measurement; Skin Temperature; Time Factors; Torque; Young Adult

Previous studies indicate that exercise-induced muscle damage may be attenuated when protein is included in a carbohydrate recovery supplement. This study was designed to examine systemic indices of muscle damage, inflammation, and recovery of muscle function, following strenuous exercise, with ingestion of either carbohydrate alone or a carbohydrate-protein mixture. Seventeen highly trained volunteers participated in 2 trials in a randomized order, separated by approximately 9 weeks. Each trial involved 90 min of intermittent shuttle-running, either with ingestion of a 9% sucrose solution during and for 4 h after (1.2 g.kg-1 body mass.h-1) or with the same solution plus 3% whey protein isolate (0.4 g.kg-1 body mass.h-1). Blood was sampled throughout and 24 h after each trial to determinate the systemic indices of muscle damage and inflammation. An isokinetic dynamometer was used to establish reliable baseline measurements of peak isometric torque for knee and hip flexors and extensors, which were then followed-up at 4-, 24-, 48-, and 168-h postexercise. The exercise protocol resulted in significantly elevated variables indicative of muscle damage and inflammation, while peak isometric torque was immediately reduced by 10%-20% relative to baseline, across all muscle groups tested. However, none of these responses varied in magnitude or time-course between the treatments, or between participants' first and second trials. The addition of whey protein isolate to a dietary carbohydrate supplement ingested during and for 4 h following strenuous exercise did not attenuate systemic indices of muscle damage or inflammation, nor did it restore muscle function more rapidly than when the carbohydrate fraction was ingested alone.

Topics: Administration, Oral; Adult; Beverages; Biomarkers; C-Reactive Protein; Creatine Kinase, MM Form; Cross-Over Studies; Dietary Sucrose; Exercise; Humans; Inflammation; Inflammation Mediators; Interleukins; L-Lactate Dehydrogenase; Lower Extremity; Male; Milk Proteins; Muscle Contraction; Muscle Strength; Muscle, Skeletal; Muscular Diseases; Myoglobin; Pain; Pain Measurement; Recovery of Function; Single-Blind Method; Time Factors; Torque; Whey Proteins; Young Adult

This study compared the effects of hot/cold water immersion, static stretching, and no recovery (control) interventions on leg strength, rowing performance, and indicators of muscle soreness/damage in the 72 hours following strenuous stair-climb running. Club (n = 14) and elite (Sports Institute) (n = 6) rowers performed the training run on three separate occasions. After each run, participants completed a randomly assigned 15-minute recovery treatment, either hot/cold, static stretching, or control, which were repeated at 24 and 48 hours postrun. No significant strength or performance differences existed between the three recovery treatments for either group. Muscle soreness for both groups remained significantly elevated (p < 0.05) above baseline at 72 hours postrun. At 48-hours postrun serum creatine kinase levels had returned to baseline and at 72 hours postrun were below baseline in both groups. In conclusion, neither hot/cold nor static stretching accelerated recovery at 72 hours beyond that achieved by the control condition.

Topics: Analysis of Variance; Biomechanical Phenomena; Creatine Kinase; Female; Humans; Immersion; Leg; Male; Muscle Stretching Exercises; Muscle, Skeletal; Pain; Physical Exertion; Recovery of Function; Running; Sports; Temperature; Torque; Western Australia; Young Adult

The association between musculoskeletal pain and decreased maximal muscle strength capacity has been extensively studied, but knowledge about functional rapid force capacity in conditions of chronic musculoskeletal pain is lacking. The objective of this study is to investigate rapid muscle activation and force capacity of chronically painful muscles.. Cross-sectional study with 42 women with chronic trapezius myalgia, and 20 healthy matched controls. Maximal capacity was determined as peak torque and peak EMG amplitude of the painful trapezius and painfree deltoid muscles during the stable high-force phase of maximal voluntary shoulder abduction, whereas rapid capacity was determined as the steepest slope of the torque-time and EMG-time curves, defined as rate of torque development and rate of EMG rise. Intensity of pain was registered prior to the test on a visual-analogue-scale.. Peak torque was 18% lower at 115 degrees shoulder joint angle in women with myalgia compared with healthy controls (P<0.001), with a corresponding 29% lower level of peak EMG specifically of the painful trapezius muscle (P<0.001). Rate of torque development was 33-54% lower (P<0.001), with a corresponding 21-35% lower level of rate of EMG rise of both the painful trapezius and painfree deltoid (P<0.0001). Intensity of pain showed higher association with parameters of rapid capacity (R=-0.33 to -0.53, P<0.001-0.05) than with maximal capacity (R=-0.15 to -0.41, P<0.01-ns).. In conditions of chronic musculoskeletal pain, the ability to rapidly activate painful and painfree synergistic muscles is more severely impaired than maximal muscle activation. These findings have clinical relevance for rehabilitation of chronically painful muscles.

Topics: Adult; Case-Control Studies; Chronic Disease; Electromyography; Female; Humans; Isometric Contraction; Kinetics; Middle Aged; Muscle Strength Dynamometer; Muscular Diseases; Neck Muscles; Pain; Rotator Cuff; Shoulder; Thorax; Torque

This study investigated whether 10 drop jumps (DJs) would confer protective effect against muscle damage and soreness in a subsequent bout of 50 DJs. Sixteen men were randomly placed into either a group performing 1 set of 10 DJs followed by 5 sets of 10 DJs (10-50, n = 8) or another group performing 2 bouts of 5 sets of 10 DJs (50-50, n = 8) separated by 2 weeks. The DJs were performed from a box height of 0.6 m, with a 10-second interval between jumps and a 1-minute rest between sets. Jump height, peak vertical ground reaction force, ground contact time, and heart rate during DJs were measured, and blood lactate concentration was assessed before and immediately after DJs. Changes in maximal isometric (ISO) and isokinetic concentric torque (CON), vertical jump, muscle soreness, and plasma creatine kinase activity before, immediately after, and at 1, 24, 48, and 72 hours following exercise were compared between groups for the first and second bouts and between the bouts by a 2-way repeated-measures analysis of variance. Changes in ISO, CON, vertical jump, and muscle soreness were significantly (p < 0.05) smaller for 10 DJs compared with 50 DJs; however, no significant differences in the measures between groups were evident following the second bout. The changes in the measures following 50 DJs in the 10-50 group were significantly (p < 0.05) smaller than those following the first bout of the 50-50 group. These results suggest that 10 DJs and 50 DJs conferred the same magnitude of protective effect against muscle damage by 50 DJs.

Topics: Athletic Injuries; Athletic Performance; Biomarkers; Creatine Kinase; Heart Rate; Humans; Knee; Lactic Acid; Male; Muscle, Skeletal; Pain; Physical Education and Training; Torque; Treatment Outcome

The objective of this study was to compare pain induced by magnetic stimulation of the quadriceps femoris (QF) muscle with that induced by transcutaneous neuromuscular electrical stimulation (NMES).. Magnetic stimulation and transcutaneous NMES were applied to QF muscles of 17 normal volunteers. The intensity of each mode of stimulation was increased in a stepwise manner. Peak torque values of isometric contractions of QF muscles and visual analog scale (VAS) scores were recorded at each intensity level. The VAS scores of the two stimulating modalities were compared at the intensity-generating same peak torque values.. The median VAS scores for electrical and magnetic stimulation were 5.7 and 0.3, respectively. The median difference between the VAS scores for electrical and magnetic stimulation was 3.7 (range, 1.7-8.5). The mean of the maximum peak torque obtained from each subject was higher in magnetic stimulation than in electrical stimulation (9.5 +/- 4.8 vs. 4.4 +/- 2.9 Nm).. Magnetic stimulation of the QF muscle produced less pain at the same level of isometric peak torque than did transcutaneous NMES. Magnetic stimulation is a potential alternative to transcutaneous NMES, especially for persons with intact or residual sensory function.

Topics: Adult; Aged; Female; Humans; Isometric Contraction; Magnetics; Male; Middle Aged; Pain; Pain Measurement; Physical Stimulation; Quadriceps Muscle; Torque; Transcutaneous Electric Nerve Stimulation

A randomized controlled trial to compare 2 forms of monophasic pulsed currents with 2 forms of burst-modulated, kilohertz-frequency alternating current ("Russian current" and "Aussie current") was conducted to establish whether different amounts of wrist extensor torque were produced and whether discomfort varied with stimulus type.. The 32 subjects were adults who were healthy and were drawn from a population of staff and students at La Trobe University.. Each subject received all 4 currents. Maximal electrically induced torque (MEIT) of the wrist extensors was measured for each stimulus type. Relative discomfort of stimulation also was assessed.. Russian current elicited lower mean torque than those elicited by Aussie current and monophasic pulsed currents. The Russian and Aussie currents elicited significantly less discomfort than the 2 monophasic pulsed currents.. When force production and relative discomfort were jointly used as the criteria, Aussie current was found to be more effective than either of the monophasic pulsed currents or Russian current stimulation.

Topics: Adult; Analysis of Variance; Australia; Electric Stimulation Therapy; Electrophysiology; Humans; Middle Aged; Muscle Contraction; Pain; Patient Acceptance of Health Care; Russia; Torque; Wrist

An inability of the nervous system to fully activate the muscle is one factor that can contribute to age-related muscle weakness. Superimposed electrical stimulation can be used to determine voluntary muscle activation (VA). The aim of this study was to assess VA of the quadriceps muscle in healthy older and younger subjects.. Electrical stimulation causes moderate discomfort in younger subjects, but no study has assessed discomfort in older subjects. The quadriceps muscle in 20 moderately active older subjects (mean age, 75 yrs) and 12 younger subjects (mean age, 25 yrs) was stimulated during two maximal voluntary contractions using a 100-Hz pulse train. A visual analog scale for pain (VAS-pain) was used to evaluate discomfort.. Ability to activate the quadriceps muscle was generally very high, and there was no significant difference between the older (mean, 0.96) and younger (mean, 0.98) subjects. Discomfort did not differ between the older (mean VAS-pain score, 41 mm) and younger (mean VAS-pain score, 37 mm) subjects.. Our results indicate that healthy, moderately active older subjects have the ability to almost complete VA of the quadriceps muscle and that discomfort during electrical stimulation is generally moderate.

Topics: Adult; Age Factors; Aged; Electric Stimulation; Female; Humans; Male; Motor Neurons; Muscle Contraction; Muscle Weakness; Pain; Pain Measurement; Quadriceps Muscle; Torque

We sought to determine if the velocity of an acute bout of eccentric contractions influenced the duration and severity of several common indirect markers of muscle damage. Subjects performed 36 maximal fast (FST, n = 8: 3.14 rad x s(-1)) or slow (SLW, n = 7: 0.52 rad x s(-1)) velocity isokinetic eccentric contractions with the elbow flexors of the non-dominant arm. Muscle soreness, limb girth, plasma creatine kinase (CK) activity, isometric torque and concentric and eccentric torque at 0.52 and 3.14 rad x s(-1) were assessed prior to and for several days following the eccentric bout. Peak plasma CK activity was similar in SLW (4030 +/- 1029 U x 1(-1)) and FST (5864 +/- 2664 U x 1(-1)) groups, (p > 0.05). Both groups experienced similar decrement in all strength variables during the 48 hr following the eccentric bout. However, recovery occurred more rapidly in the FST group during eccentric (0.52 and 3.14 rad x s(-1)) and concentric (3.14 rad x s(-1)) post-testing. The severity of muscle soreness was similar in both groups. However, the FST group experienced peak muscle soreness 48 hr later than the SLW group (24 hr vs. 72 hr). The SLW group experienced a greater increase in upper arm girth than the FST group 20 min, 24 hr and 96 hr following the eccentric exercise bout. The contraction velocity of an acute bout of eccentric exercise differentially influences the magnitude and time course of several indirect markers of muscle damage.

Topics: Adult; Arm; Biomarkers; Creatine Kinase; Exercise; Female; Humans; Male; Muscle Contraction; Muscle, Skeletal; Pain; Physical Education and Training; Torque

While various models for exercise-induced muscle damage (EIMD) have been introduced, many of them use maximal voluntary contractions of the elbow flexors and knee extensors performed on isokinetic dynamometers. Few studies have used exercise protocols that attempt to replicate submaximal eccentric muscle actions that commonly occur during daily activities. Downhill backwards walking has been used previously as an EIMD model. However, the common markers of muscle damage have not been systematically examined for this model. The purpose of this study was to determine the magnitude of muscle damage induced by downhill backward walking with regard to changes in commonly-used indirect markers of EIMD. Twenty subjects aged between 19 y and 42 y completed a bout of 60 min of downhill (-15%) backward walking in which a single limb performed submaximal eccentric actions at a stepping rate of 30 - 35 strides per min. A repeated measures ANOVA revealed significant (p < 0.05) increases from baseline for soreness (24 hr- 96 hr), tenderness (24 hr - 96 hr), and plasma creatine kinase activity (0.5 hr - 96 hr), and significant decreases (p < 0.05) in maximal voluntary isometric (approximately 25%) and isokinetic (-15%) strength (0.5 hr - 96 hr) post-walk for the exercised limb. The time course of observed changes in these markers was similar to that reported for EIMD models of the elbow flexors and knee extensors. However, the magnitude of muscle damage appeared more consistent with that demonstrated following submaximal eccentric exercise.

Topics: Adult; Analysis of Variance; Biomarkers; Creatine Kinase; Heart Rate; Humans; Muscle, Skeletal; Pain; Torque; Walking

There is growing evidence that reactive oxygen species (ROS) are involved in the muscular damage and soreness that is observed following strenuous or unaccustomed exercise. This study investigated the relationship between delayed onset muscle soreness (DOMS), muscle function and ROS following downhill running using electron spin resonance (ESR) spectroscopy and plasma malonaldehyde (MDA) concentrations. Eight physically active male subjects participated in two trials consisting of 30 min of running at approximately 65% VO(2max) on the flat (FLA) or a 15% downhill (DWN) gradient. Venous blood samples were drawn before, immediately after, and then 24, 48 and 72 h post exercise, and at the same time DOMS and muscle function were assessed. Blood was analysed for markers of ROS, total and differential white blood cell count, and creatine kinase. Muscle function was measured on an isokinetic dynamometer, whilst DOMS was assessed using a visual analogue scale. An increase in ROS, detected via ESR spectroscopy and MDA, was observed following DWN ( P<0.05) but not following FLA. Increased DOMS and loss of muscle function were observed following DWN ( P<0.05) but not following FLA ( P>0.05). DWN resulted in a transient leukocytosis ( P<0.05) occurring immediately post-exercise but returning to pre-exercise levels by 24 h. Although DWN resulted in an increase in ROS production, the increase occurred after the peak decline in muscle function and DOMS, suggesting that there may be a disassociation in the temporal relationship between ROS, loss of muscle function and DOMS.

Topics: Adult; Exercise; Humans; Male; Malondialdehyde; Muscle Contraction; Muscle, Skeletal; Pain; Physical Exertion; Reactive Oxygen Species; Running; Statistics as Topic; Time Factors; Torque

The purpose of this study was to compare changes in performance indicators (power, torque, and velocity) and muscle soreness between plyometric training on land and in water. Thirty-two college age women were randomly assigned to 8 weeks of an identical plyometric training program on land or in an aquatic setting. Performance indicators were assessed pretraining, midtraining, and posttraining. Muscle soreness (ordinal scale) and pain sensitivity (palpation) were assessed after a training bout (0, 48, and 96 hours) during the first week of training and when training intensity was increased (weeks 3 and 6). Performance indictors increased for both groups (pretraining < midtraining < posttraining, p < or = 0.001). Muscle soreness was significantly greater in the land compared to the aquatic plyometric training group at baseline and each time training intensity was increased, p = 0.01. Aquatic plyometrics provided the same performance enhancement benefits as land plyometrics with significantly less muscle soreness.

Topics: Exercise; Female; Humans; Linear Models; Multivariate Analysis; Muscle, Skeletal; Pain; Physical Education and Training; Swimming Pools; Torque

To assess the force required for, and pain of, removal of the GyneFix as compared with T-framed intrauterine devices (IUDs).. A comparative trial following patient-blinded randomisation in an outpatient clinic setting.. Women requesting an IUD for emergency contraception were fitted with either a GyneFix or a Gyne-T380S. For those requesting removal of the IUD, visual analogue scores were used to assess their perception of the associated pain, and a Newton dynamometer was used to measure the force required to remove the device.. Removal required significantly more force for GyneFix as compared with Gyne-T380S (p = 0.004), but there was no significant difference in pain perceived by women during removal. Interestingly, anticipated pain was worse than actual pain experienced.. Although more force is needed to remove the GyneFix as compared with the Gyne-T380S, this does not translate into more pain.

Topics: Adolescent; Adult; Device Removal; Emergency Treatment; Female; Humans; Intrauterine Devices, Copper; London; Pain; Pain Measurement; Patient Acceptance of Health Care; Pregnancy; State Medicine; Torque

The purpose of this study was to compare changes in muscle damage indicators following 24 maximal eccentric actions of the elbow flexors (Max-ECC) between the arms that had been previously trained either eccentrically or concentrically for 8 wk.. Fifteen subjects performed three sets of 10 repetitions of eccentric training (ECC-T) with one arm and concentric training (CON-T) with the other arm once a week for 8 wk using a dumbbell representing 50% of maximal isometric force of the elbow flexors (MIF) determined at the elbow joint of 90 degrees (1.57 rad). The dumbbell was lowered from a flexed (50 degrees, 0.87 rad) to an extended elbow position (180 degrees, 3.14 rad) in 3 s for ECC-T, and lifted from the extended to the flexed position in 3 s for CON-T. Max-ECC was performed 4 wk after CON-T and 6 wk after ECC-T. Changes in MIF, range of motion (ROM), upper arm circumference (CIR), muscle soreness (SOR), and plasma creatine kinase (CK) activity were compared between the ECC-T and CON-T arms.. The first ECC-T session produced larger decreases in MIF and ROM, and larger increases in CIR and SOR compared with CON-T. CK increased significantly (P < 0.01) and peaked 4 d after the first training session, but did not increase in the following sessions. All measures changed significantly (P < 0.01) following Max-ECC; however, the changes were not significantly different between ECC-T and CON-T arms.. These results showed that ECC-T did not mitigate the magnitude of muscle damage more than CON-T, and CON-T did not exacerbate muscle damage.

Topics: Adaptation, Physiological; Adolescent; Adult; Anthropometry; Arm; Athletic Injuries; Creatine Kinase; Elbow; Exercise; Humans; Isometric Contraction; Male; Muscle, Skeletal; Pain; Physical Education and Training; Range of Motion, Articular; Torque; Weight Lifting

Eight patients with patellar pain underwent knee proprioceptive training. The maximal knee extension torque associated with the Vastus Lateralis EMG signal increased (p 0.001 and 0.039). Although muscle balance was not improved, all the patients improved their clinical scores.

Topics: Female; Humans; Knee; Male; Muscle, Skeletal; Pain; Patella; Physical Therapy Modalities; Proprioception; Torque

A between groups design was used to compare recovery following eccentric muscle damage under 2 experimental conditions.. To determine if a compression sleeve donned immediately after maximal eccentric exercise would enhance recovery of physical function and decrease symptoms of soreness.. Prior investigations using ice, intermittent compression, or exercise have not shown efficacy in relieving symptoms of delayed onset muscle soreness (DOMS). To date, no study has shown the effect of continuous compression on DOMS, yet this would offer a low cost intervention for patients suffering with the symptoms of DOMS.. Twenty nonimpaired non-strength-trained women participated in the study. Subjects were matched for age, anthropometric data, and one repetition maximum concentric arm curl strength and then randomly placed into a control group (n = 10) or an experimental compression sleeve group (n = 10). Subjects were instructed to avoid pain-relieving modalities (eg, analgesic medications, ice) throughout the study. The experimental group wore a compressive sleeve garment for 5 days following eccentric exercise. Subjects performed 2 sets of 50 passive arm curls with the dominant arm on an isokinetic dynamometer with a maximal eccentric muscle action superimposed every fourth passive repetition. One repetition maximum elbow flexion, upper arm circumference, relaxed elbow angle, blood serum cortisol, creatine kinase, lactate dehydrogenase, and perception of soreness questionnaires were collected prior to the exercise bout and daily thereafter for 5 days.. Creatine kinase was significantly elevated from the baseline value in both groups, although the experimental compression test group showed decreased magnitude of creatine kinase elevation following the eccentric exercise. Compression sleeve use prevented loss of elbow motion, decreased perceived soreness, reduced swelling, and promoted recovery of force production.. Results from this study underline the importance of compression in soft tissue injury management.

Topics: Adolescent; Adult; Anthropometry; Arm Injuries; Bandages; Creatine Kinase; Elbow Joint; Exercise; Female; Humans; Hydrocortisone; L-Lactate Dehydrogenase; Muscle Fatigue; Muscle, Skeletal; Pain; Pain Management; Pain Measurement; Physical Therapy Modalities; Range of Motion, Articular; Recovery of Function; Soft Tissue Injuries; Torque; Weight Lifting

Many symptoms of eccentric muscle damage can be substantially reduced if a similar eccentric bout is repeated within several weeks of the initial bout. The purpose of this study was to determine whether a nondamaging, low repetition, low volume eccentric exercise bout could also provide a protective/adaptive effect.. Subjects were assigned to a control (CON), eccentric exercise (ECC), or low volume familiarized eccentric exercise group (LV+ECC). Before the study, the LV+ECC group performed six maximal eccentric contractions during two familiarization sessions. The main eccentric bout targeted the elbow flexor muscle group and consisted of 36 maximal eccentric contractions. Muscle soreness, upper arm girth, elbow angle, creatine kinase activity, isometric torque, and concentric and eccentric torque at 0.52 and 3.14 rad.s-1 were assessed 0, 1, 2, 3, 4, 7, and 10 d postexercise.. No evidence of muscle damage was observed as a result of the low volume eccentric bouts. Nevertheless, with the exception of muscle soreness and concentric torque, all variables recovered more rapidly in the LV+ECC group (P < 0.05).. Adaptation to eccentric exercise can occur in the absence of significant muscle damage. Exposure to a small number of nondamaging eccentric contractions can significantly improve recovery after a subsequent damaging eccentric bout. Furthermore, this adaptation appears to be mode-specific and not applicable to concentric contractions.

Topics: Adaptation, Physiological; Adult; Arm; Creatine Kinase; Exercise; Female; Humans; Isometric Contraction; Male; Muscle, Skeletal; Pain; Torque

The purpose of this study was to examine the effects of simultaneously delivering 2 channels of electromyostimulation (EMS) current using 2 different electrode arrangements. Ten men and 10 women university students had 4 reusable electrodes placed (2 proximal, 2 distal) medial and lateral on the quadriceps muscle group. Isokinetic voluntary peak torque (VPT) of the quadriceps was determined at 60 degrees x s(-1). A symmetrical biphasic square wave current was applied using 2 independent channels in either a parallel (P) or a crossed (X) electrode arrangement. Subjects increased the current until maximal tolerance was achieved. No significant differences in percent VPT or perceived discomfort (PD) were observed between men and women. Percent VPT was significantly greater using the X (57.2 +/- 11.3%) vs. the P (46.5 +/- 10.7%) pad placement; however, pad placement did not affect peak PD. Data from this study suggest that a 2-channel application of EMS using a crossed electrode arrangement provides greater knee extensor force without greater discomfort.

Topics: Adult; Electric Stimulation; Electrodes; Female; Humans; Isometric Contraction; Knee; Male; Muscle Contraction; Muscle, Skeletal; Pain; Perception; Sex Characteristics; Torque

The goals of the study were to measure the force applied to the lateral side of the knee by a valgus loading brace designed for patients with medial compartment osteoarthritis (OA) and to compare the varus moment at the knee during level gait with and without the brace.. Five subjects diagnosed with medial compartment OA were fitted with a custom Monarch valgus loading knee brace. A 3-dimensional videobased motion analysis system and force plate information were used to calculate forces and moments at the knee. An instrumented condylar bladder was used to determine the force applied to the knee by the brace. The varus moments for the braced and unbraced trials were compared during gait at 15%, 20%, 25%, and 30% of stance.. The Monarch brace significantly reduced the varus moment at 20% and 25% of stance. The valgus force measured with the custom condylar bladder remained fairly constant throughout the first 80% of the stance phase.. The reduced various moment observed for the braced condition demonstrates the biomechanical function of the brace in 5 subjects and may contribute to a reduction of pain for patients with medial compartment OA.

Topics: Activities of Daily Living; Adult; Analysis of Variance; Biomechanical Phenomena; Braces; Equipment Design; Female; Gait; Humans; Male; Middle Aged; Osteoarthritis, Knee; Pain; Range of Motion, Articular; Torque; Treatment Outcome; Videotape Recording; Weight-Bearing

To assess the hypothesis that Farabloc, a fabric with electromagnetic shielding properties, would attenuate the symptoms, signs, and muscular strength deficit secondary to delayed-onset muscle soreness (DOMS) induced by two exposures to eccentric exercise in humans.. Randomized, single-blind, placebo-controlled, crossover trial with two testing stages of 5 days duration separated by a washout period of more than 8 weeks.. University-based sports medicine center.. Twenty volunteers equally representing untrained male and female subjects.. 20 sets of 10 repetitions of single-leg eccentric knee extensions for 37 minutes with the Biodex dynamometer set at 30 degrees per second were performed on the first day of stage one and stage two to induce DOMS in the quadriceps muscle. Double layers of fabric, either Farabloc or placebo, were wrapped around the thigh of each participant during each stage for 5 days.. Perception of muscle pain, as measured by a visual analog scale (VAS), and strength, as measured by knee extensor torque (EST) with the Biodex dynamometer, were evaluated at 0, 24, 48, 72, and 96 hours. Serum inflammatory markers of muscle damage, including malondialdehyde. creatine phosphokinase, myoglobin, leukocytes, and neutrophils, were assayed at 0, 2, 6, 24, and 48 hours.. Repeated-measures analysis of variance was carried out for each of the seven variables to assess differences for fabric, order of treatment, time, and all combinations. Results of VAS and EST and levels of malondialdehyde, creatine phosphokinase, myoglobin, leukocytes, and neutrophils all showed a highly significant effect of Farabloc compared with placebo. This analysis shows that the order of Farabloc or placebo fabric use in stage I and 2 produces different results. This may be caused by a learning effect, but did not alter the overall influence of Farabloc.. The data indicate that double layers of Farabloc fabric wrapped around the thigh reduces pain and strength loss and serum levels of malondialdehyde, creatine phosphokinase, myoglobin, leukocytes, and neutrophils when untrained human subjects are exposed to eccentric exercise to produce DOMS in the quadriceps. Farabloc shields high-frequency electromagnetic fields, although the results do not indicate how these changes are mediated. Further research is needed to determine the mechanism.

Topics: Adult; Analysis of Variance; Biomarkers; Creatine Kinase; Cross-Over Studies; Electromagnetic Fields; Female; Follow-Up Studies; Humans; Knee Joint; Leukocyte Count; Male; Malondialdehyde; Muscle Contraction; Muscle, Skeletal; Myoglobin; Neutrophils; Pain; Pain Measurement; Physical Exertion; Placebos; Radiation Protection; Range of Motion, Articular; Single-Blind Method; Torque

This study examined markers of muscle damage following a repeated bout of maximal isokinetic eccentric exercise performed prior to full recovery from a previous bout. Twenty non-resistance trained volunteers were randomly assigned to a control (CON, n=10) or experimental (EXP, n=10) group. Both groups performed 36 maximal isokinetic eccentric contractions of the elbow flexors of the non-dominant arm (ECC1). The EXP group repeated the same eccentric exercise bout two days later (ECC2). Total work and peak eccentric torque were recorded during each set of ECC1 and ECC2. Isometric torque, delayed onset muscle soreness (DOMS), flexed elbow angle and plasma creatine kinase (CK) activity were measured prior to and immediately following ECC1 and ECC2. at 24h intervals for 7 days following ECC1 and finally on day 11. In both groups, all dependent variables changed significantly during the 2 days following ECC1. A further acute post-exercise impairment in isometric torque (30 +/- 5%) and flexed elbow angle (20 +/- 4%) was observed following ECC2 (p<0.05), despite EXP subjects producing uniformly lower work and peak eccentric torque values during ECC2 (p<0.05). No other significant differences between the CON and EXP groups were observed throughout the study (p>0.05). These findings suggest that when maximal isokinetic eccentric exercise is repeated two days after experiencing of contraction-induced muscle damage, the recovery time course is not significantly altered.

Topics: Adult; Analysis of Variance; Arm Injuries; Creatine Kinase; Elbow; Elbow Injuries; Elbow Joint; Exercise; Female; Humans; Isometric Contraction; Male; Muscles; Pain; Recurrence; Statistics, Nonparametric; Time Factors; Torque

Unaccustomed exercise (usually of an eccentric nature) is often followed by delayed onset muscle soreness (DOMS). Previous studies have found that prior eccentric activity produces a training effect which reduces DOMS and morphological changes. The aim of this study was to examine the effects of a prior bout of maximal isokinetic eccentric exercise on DOMS, strength loss and plasma creatine kinase (CK) changes following a downhill run. Ten male subjects with a mean (+/- S.D.) age of 22.5 +/- 2.8 years, body mass of 62.67 +/- 0.05 kg and height of 176 +/- 3 cm were allocated to either a treatment group or a control group. The treatment group performed 100 maximal eccentric activations of the knee extensors in the dominant leg at 0.52 rad s-1. Two weeks later, the downhill run was performed on a motor-driven treadmill. This consisted of five bouts of 8 min at a gradient of -10% at a speed corresponding to 80% of the predicted maximal heart rate. The untrained group performed the downhill run as above but without the prior isokinetic session. Tenderness measurements, plasma CK activity and concentric and eccentric isokinetic peak torque measurements of the knee extensors at 0.52 and 2.83 rad s-1 were recorded prior to, immediately following and 2, 4 and 7 days after each protocol. The isokinetic protocol caused an increase (P < 0.01) in CK and tenderness and a decrease (P < 0.05) in concentric and eccentric torque at both speeds in the treatment group. Following the downhill run, a reduction in peak torque (P < 0.01) was observed in the eccentric and concentric modes at both isokinetic speeds in the control group. For the treatment group, the decrease in peak torque occurred only at the faster eccentric speed. With the exception of the faster eccentric speed, the decrement in peak torque was greater in the control group in all post-exercise isokinetic strength tests. There was less tenderness (P < 0.01) in the trained knee extensor muscle group. Peak torque also returned to pre-downhill values earlier for the trained group. Although plasma CK activity increased in both groups after downhill running, it was much lower (P < 0.01) in the trained group. The results suggest that a prior bout of isokinetic eccentric training reduces muscle damage, reduces the amount of strength loss and decreases the sensation of DOMS after downhill running.

Topics: Adult; Analysis of Variance; Creatine Kinase; Exercise Test; Follow-Up Studies; Heart Rate; Humans; Knee Joint; Male; Muscle Contraction; Muscle, Skeletal; Pain; Physical Exertion; Running; Torque

Neuromuscular function is altered acutely following concussion and theoretically linked to the subsequent postconcussion musculoskeletal injury risk. Existing research has only examined voluntary muscle activation, limiting mechanistic understanding. Therefore, our study aimed to examine voluntary and involuntary muscle activation between college-aged, concussed individuals when symptom-free and healthy matched controls.. Prospective, cross-sectional cohort laboratory study.. Concussed and healthy participants (n = 24; 58% male, age: 19.3 [1.1] y, mass: 70.3 [16.4] kg, height: 177.3 [12.7] cm) completed the superimposed burst (SB) neuromuscular assessment on their dominant limb within 72 hours after self-reporting asymptomatic (22.4 [20.2] d postinjury). Unnormalized and bodyweight-normalized quadriceps maximal voluntary isometric contraction torque (in newton meters), unnormalized and bodyweight-normalized electrically stimulated SB torque, pain (numeric 1-10) during SB, and the central activation ratio (in percentage) were assessed via the SB. Parametric and nonparametric analyses, 95% confidence intervals (95% CIs), and Hedges g (parametric) and Spearman ρ (nonparametric) effect sizes were used to examine group differences (α = .05).. The maximal voluntary isometric contraction torque (concussed: 635.60 N·m [300.93] vs control: 556.27 N·m [182.46]; 95% CI, -131.36 to 290.02; P = .443; d = 0.33), SB torque (concussed: 203.22 N·m [97.17], control: 262.85 N·m [159.07]; 95% CI, -171.22 to 51.97; P = .280; d = -0.47), and central activation ratio (concussed: 72.16% [17.16], control: 70.09% [12.63]; 95% CI, -10.68 to 14.83; P = .740; d = 0.14) did not differ between the concussed and control groups regardless of bodyweight normalization (P ≥ .344). Pain during the SB was significantly higher with a medium effect for participants with a concussion versus healthy controls (concussed: median = 7, control: median = 5; P = .046; ρ = -0.42).. These findings suggest concussed participants do not have statistically altered voluntary or involuntary quadricep neuromuscular function once asymptomatic compared with controls. Therefore, the elevated postconcussion musculoskeletal injury risk may not be attributed to lower-extremity muscle activation. Concussed participants displayed greater pain perception during the SB, which suggests somatosensory or perception changes requiring further examination.

Topics: Adult; Brain Concussion; Cross-Sectional Studies; Female; Humans; Lower Extremity; Male; Pain; Prospective Studies; Quadriceps Muscle; Torque; Young Adult

Topics: Electromyography; Exercise; Humans; Isometric Contraction; Muscle, Skeletal; Pain; Quadriceps Muscle; Torque

Little is known about how the combination of pain severity and duration affects quadriceps function and self-reported function in patients with anterior knee pain (AKP).. To examine how severity (low [≤3 of 10] versus high [>3 of 10]) and duration (short [<2 years] versus long [>2 years]) of AKP affect quadriceps function and self-reported function.. Cross-sectional study.. Laboratory.. Sixty patients with AKP (mean pain severity = 4 of 10 on the numeric pain rating scale, mean pain duration = 38 months) and 48 healthy control individuals. Patients with AKP were categorized into 3 subdivisions based on pain: (1) severity (low versus high); (2) duration (short versus long); and (3) severity and duration (low and short versus low and long versus high and short versus high and long).. Quadriceps maximal (maximal voluntary isometric contraction) and explosive (rate of torque development) strength, activation (central activation ratio), and endurance (average peak torque) and self-reported function (Lower Extremity Functional Scale score).. Compared with the healthy control group, (1) all AKP subgroups showed less quadriceps maximal strength (P < .005, d ≥ 0.78) and activation (P < .02, d ≥ 0.85), except for the AKP subgroup with low severity and short duration of pain (P > .32); (2) AKP subgroups with either high severity or long duration of pain showed less quadriceps explosive strength (P < .007, d ≥ 0.74) and endurance (P < .003, d ≥ 0.79), but when severity and duration were combined, only the AKP subgroup with high severity and long duration of pain showed less quadriceps explosive strength (P = .006, d = 1.09) and endurance (P = .0004, d = 1.21); and (3) all AKP subgroups showed less self-reported function (P < .0001, d ≥ 3.44).. Clinicians should be aware of the combined effect of severity and duration of pain and incorporate both factors into clinical practice when rehabilitating patients with AKP.

Topics: Cross-Sectional Studies; Humans; Knee Joint; Muscle Strength; Pain; Quadriceps Muscle; Self Report; Torque

This study aimed to determine the intra-day reliability, individuals performance expectancy, and biomechanical response of nine stretching instructions in assessing the maximal range of motion (mROM) during the passive ankle dorsiflexion test. Twenty healthy young participants were tested in two sessions within the same day. Nine stretching instructions composed by intensity-domain (i.e. minimum, point, and maximum) and sensation-domain (i.e. tolerance, discomfort, and pain) words were used to impose plantar flexors stretching. In the first session, individuals were requested to order the nine stretching instructions in ascending order. The ankle joint torque-angle and medial gastrocnemius, soleus and tibialis anterior electric activity were assessed in both sessions. A moderate to high reliability was observed across instructions (ICC = 0.65-0.87). Most stretching instructions showed high intra-day reliability outcomes, where discomfort and tolerance showed moderate reliability. 70% of individuals performed the stretching maneuvers consistently to stretching instructions performance expectancy. A greater torque-angle response was observed for the instructions involving the word pain (ROM = 40.5 ± 1.6°), compared to discomfort (29.5 ± 1.8°), and tolerance (30.5 ± 2.0°) that produced similar stretching intensities. Instructions involving the terms minimum (29.6 ± 2.0°), point (33.3 ± 7.6°), and maximum (37.6 ± 7.2°) were more discriminative of stretching intensities than sensation-domain terms. In conclusion, stretching instructions targeting the joint maximal range of motion produce different joint torque-angle responses and they may not be understandable by all individuals, although (in general) they can be used reliably.

Topics: Ankle Joint; Humans; Muscle Stretching Exercises; Muscle, Skeletal; Pain; Range of Motion, Articular; Reproducibility of Results; Torque

In this study, we aimed to identify the time course effects of different intensities of static stretch (SST) (maximal intensity without pain vs. high-intensity with moderate pain) on flexibility. This study included 16 healthy students (8 men and 8 women) who performed 1) 5-minute SST at 100%, 2) 110%, and 3) 120% intensity, as well as 4) no stretching (control) in a random sequence on four separate days. Static passive torque (SPT), hamstring electromyography (EMG), and pain intensity were continuously recorded during SST. We assessed markers of stiffness, range of motion (ROM), and maximal dynamic passive torque (DPTmax) before SST and 0, 15, 30, 45, 60, 75, and 90 minutes after SST. Stiffness decreased and ROM and DPTmax increased significantly immediately after SST at the three different intensity levels (

Topics: Electromyography; Female; Humans; Male; Muscle, Skeletal; Pain; Range of Motion, Articular; Torque

Knee osteoarthritis (OA) is a prevalent disabling disease among women and quadriceps weakness is attributed to one of the causes of knee pain (KP) and disability. The study aimed to test the correlation of eccentric quadriceps torque (EQT) with 2 subscales of the reduced WOMAC questionnaire (KP and physical function) and extension lag range of motion (ROM) at the knee joint in osteoarthritic women. A cross-sectional design was used. A total of 70 patients (mean age 41.1 years) who had grade I or II knee OA participated in the study. The pearson correlation coefficient was used to test the correlation between the EQT and 2 subscales of the reduced WOMAC questionnaire and extension lag ROM. EQT presented a significant moderate negative correlation with pain (r = -0.489, P < .001) and physical function (r = -0.425, P < .001), and low positive correlation with available ROM (R = 0.349, P < .001). KP, physical function, and extension lag in the early stages of knee OA in women are associated with EQT. Therefore, designing a rehabilitation program that has eccentric quadriceps strengthening exercises may improve KP and physical activities, but more randomized controlled trials are needed to verify this.

Topics: Adult; Cross-Sectional Studies; Female; Humans; Knee Joint; Muscle Strength; Osteoarthritis, Knee; Pain; Quadriceps Muscle; Range of Motion, Articular; Torque

To examine changes in muscle thickness (MT), soreness (SOR), and isometric torque (ISO) following exercise with pulsed direct current (Neubie) or traditional high-load (TRAD) exercise.. Thirty-two participants had SOR, MT, and ISO measured before, immediately after, and 24 and 48h following TRAD and Neubie. Rating of perceived exertion (RPE) and discomfort were also measured. Results are displayed as means(SD).. For MT, there was a condition x time interaction (p<0.001). For Neubie, MT increased pre [3.7(0.7)cm] to post [3.9(0.8) cm, p<0.001] and remained elevated at 24h. For TRAD, MT increased pre [3.7(0.6)cm] to post [4.0 (0.7)cm, p<0.001] and remained up to 48h. Greater values were observed for TRAD post-exercise. For ISO, both conditions decreased up to 48h. TRAD demonstrated a greater change post exercise (p<0.001). For SOR, both conditions increased up to 48h. Neubie demonstrated greater SOR at 48h (p=0.007). RPE was higher for all sets in TRAD [Mean across sets=16.0(1.9) vs. 13.5(2), p<0.001]. Discomfort was higher in all sets for Neubie [Mean across sets=5.8(1.5)vs. 4.5(2.0), p<0.05].. Both conditions showed increased SOR, and decreased ISO for up to 48h, with MT increased for up to 24h. MT remained elevated in TRAD at 48h. Neubie training might be effective for individuals who are looking to experience lower RPE responses during exercise.

Topics: Exercise; Humans; Muscle, Skeletal; Pain; Resistance Training; Torque

The aim of this study was to assess the insertion torque of the mini-implant used in orthodontic patients and to assess the correlation between the insertion torque, primary stability, and perception of pain in patients undergoing orthodontic therapy with mini-implant-augmented anchorage.. Among the patients undergoing orthodontic therapy, 31 samples who required mini-implant for anchorage purpose were selected. A total of 59 mini-implants were placed in these patients. This included interradicular mini-implants and extra-alveolar mini-screws. Immediately after placement, the insertion torque in all these was measured using a digital torque meter and primary stability was assessed by identifying any mobility of the implant placed. Primary stability was noted at two time intervals immediate post-placement and 1 week after that. All the mini-implants that were considered in this study were immediately loaded. Patients were asked to record any pain experienced on the visual analog scale (VAS) score sheet at 24 hours and 1 week post-placement.. Among the mini-implants placed, those with 2 mm diameter needed higher placement torque, i.e., infrazygomatic crest mini-implants and buccal shelf mini-implants were placed with average placement torque of 10.08 and 10.25 N cm, respectively. Extra-alveolar screws caused more pain, especially higher in the mandible than the maxilla. Decrease in pain scores was noted from T0 to T1 in almost all the cases.. Thicker mini-implant needed more insertion torque and highest insertion torque was recorded with extra-alveolar screws. No direct correlation could be obtained with the pain levels experienced by the patients and with the primary stability of the mini-implants.. Mini-implants placed with an insertion torque above the recommended range tend to fail and break more often. Patients placed with extra-alveolar bone screws reported more pain than that of the smaller-dimension mini-implant.

Topics: Dental Implants; Humans; Mandible; Orthodontic Anchorage Procedures; Pain; Torque

Muscular (i.e., quadriceps) weakness contributes to disease progression and precedes the appearance of patient-reported symptoms, such as pain and perceived physical dysfunction, in knee osteoarthritis (OA). It is unknown, however, if muscular-based and patient-reported outcomes differentially associate with systemic biomarkers reflective of the local mediators in knee OA. The purpose of this study was to identify if muscular-based and patient-reported outcomes differentially associate with circulating superoxide dismutase (SOD) and cytokines in knee OA. Subjects (n = 29) with pain, muscular weakness, and radiographic evidence (Kellgren-Lawrence grade ≥2) of knee OA in the involved (INV) leg were included in this study. Serum Cu/Zn and Mn SOD and cytokine concentrations were measured in fasting blood samples. Pain and physical dysfunction were subjectively assessed and muscle strength (i.e., peak isometric force and torque, and peak isokinetic-concentric knee-extension and -flexion torques) was determined unilaterally in the INV and non-involved (NI) legs. Peak isometric and peak isokinetic-concentric knee-flexion torques in the INV leg correlated with serum Cu/Zn SOD (both p < 0.05). Peak isometric force and torque and peak isokinetic-concentric knee-extension and -flexion torques in the INV leg correlated with serum Mn SOD (all p < 0.05). Pain and dysfunction inversely associated with serum IL-1β, IL-4, IL-5, IL-12, IL-13, and/or IFN-γ (p < 0.05). Neither SOD associated with pain or dysfunction, and none of the cytokines associated with muscular-based outcomes. We conclude that common outcome measures used in the clinical evaluation of OA differentially associate with circulating SOD and cytokines.

Topics: Biomarkers; Cytokines; Female; Humans; Male; Middle Aged; Muscle Strength; Osteoarthritis, Knee; Pain; Patient Reported Outcome Measures; Quadriceps Muscle; Superoxide Dismutase; Torque

Background and aims The effect of stretching on joint range of motion is well documented and is primarily related to changes in the tolerance to stretch, but the mechanisms underlying this change are still largely unknown. The aim of this study was to investigate the influence of a remote, painful stimulus on stretch tolerance. Methods Thirty-four healthy male subjects were recruited and randomly assigned to an experimental pain group (n=17) or a control group (n=17). Passive knee extension range of motion, the activity of hamstring muscles and passive resistive torque were measured with subjects in a seated position. Three consecutive measures were performed with a 5-min interval between. A static stretch protocol was utilized in both groups to examine the effect of stretching and differences in stretch tolerance between groups. Following this, the pain-group performed a cold pressor test which is known to engage the endogenous pain inhibitory system after which measurements were repeated. Results A significant increase in knee extension range of motion was found in the pain group compared with controls (ANCOVA: p<0.05). No difference was found in muscle activity or passive resistive torque between groups (ANCOVA p>0.091). Conclusions Passive knee extension range of motion following stretching increased when following a distant, painful stimulus, potentially engaging the endogenous pain inhibitory systems. Current findings indicate a link between increased tolerance to stretch and endogenous pain inhibition. Implications The current findings may have implications for clinical practice as they indicate that a distant painful stimulus can influence range of motion in healthy individuals. This implies that the modulation of pain has significance for the efficacy of stretching which is important knowledge when prescribing stretching as part of rehabilitation.

Topics: Adult; Hamstring Muscles; Humans; Knee; Male; Muscle Stretching Exercises; Pain; Range of Motion, Articular; Torque; Young Adult

To investigate the effects of acute experimental knee joint pain on maximum force generation and rate of force development (RFD) of the quadriceps muscle during isometric and dynamic muscle activations.. The right knee of 20 healthy people was injected with hypertonic saline to create an acute pain experience. Measurements of maximum knee extensor torque during isometric, concentric, and eccentric contractions were undertaken using a Biodex dynamometer. The RFD was also examined during the isometric contractions. Quadriceps muscle activity was obtained using electromyography (EMG). The outcome measures were obtained at baseline, during pain, and after knee pain had resolved.. Maximum joint torque and peak EMG were significantly reduced during pain, but there were no differences across the three types of contraction. The maximum RFD and rate of EMG rise were also reduced during pain, primarily at 50-100 ms post-contraction onset. The RFD and EMG rise were largely unaffected at later time periods following contraction onset (150-200 ms).. Acute joint pain has a similar impact on isometric and isokinetic contractions despite differences in neural control strategies. Joint pain also impairs rapid muscle activation and the RFD. These findings are important for people with musculoskeletal pain as it likely contributes to impairments in joint function in these populations.

Topics: Adolescent; Adult; Electromyography; Exercise; Female; Humans; Isometric Contraction; Knee; Knee Joint; Male; Middle Aged; Movement; Muscle Contraction; Muscle Strength; Pain; Quadriceps Muscle; Torque; Young Adult

We examined the fatigue and recovery for 48h following a full-body resistance exercise session in trained men.. Experimental cross-sectional study.. Eight resistance trained men volunteered to participate (mean±SD; age 27.0±6.0 years, height 1.79±0.05m, weight 81.8±6.8kg, training experience 7.8±5.0 years). Fatigue and pain was measured before, after, 1h post, 24h and 48h post the full-body resistance exercise session, which was based on in-season models used in contact team sports (e.g. AFL, NRL). Other measures included maximal torque and rate of torque development, central motor output (quadriceps muscle activation, voluntary activation, H-reflexes), and muscle contractility (evoked twitch responses). Linear mixed-model ANOVA procedures were used for data analysis.. Fatigue, soreness, and muscle pain did not return to pre-exercise levels until after 48h rest. Quadriceps maximal torque and muscle contractility were reduced from pre-exercise (p<0.01), and did not return to pre-exercise levels until 24h. Early rates of torque development and muscle activation were unchanged. The amplitude and slope of the normalized quadriceps H-reflex was higher immediately after exercise (p<0.05).. Full-body resistance exercise including multiple lower limb movements immediately reduced maximal torque, muscle contractility, and increased pain. While recovery of voluntary and evoked torque was complete within a day, 48h rest was required for fatigue and pain to return to baseline. Maximal voluntary effort may be compromised for lower-limb training (i.e. sprinting, jumping) prescribed in the 48h after the session.

Topics: Adult; Cross-Sectional Studies; Electromyography; Humans; Male; Muscle Contraction; Muscle Fatigue; Muscle, Skeletal; Pain; Quadriceps Muscle; Resistance Training; Rest; Torque; Young Adult

To compare knee torque, range of motion, quality of movement, and morphology in dominant and nondominant legs of male adolescent basketball players with and without anterior knee pain and untrained peers.. Cross-sectional.. Sports performance laboratory.. Male basketball players aged 14-15 years with and without anterior knee pain and healthy untrained subjects (n = 88).. Basketball players were allocated to a symptomatic or asymptomatic group based on self-reported anterior knee pain. Associations between pain and body mass, height, passive range of motion, muscle peak torque, coactivation, neuromuscular control, proprioception, and ultrasound observations were investigated.. The prevalence of pain did not differ significantly between sides. Of 176 knees inspected, 44 were painful, and 26 of these exhibited abnormalities in ultrasonography. Symptomatic players were 5.0 and 6.9 cm taller than asymptomatic players and controls, respectively (P < 0.05). In athletes with knee pain, the odds ratios of morphological abnormalities and greater height were increased by 8.6 and 5.0 times (P < 0.001).. Knee pain prevalence in adolescent basketball players was not related to differences between sides but was higher in tall players. Knee pain was accompanied by morphological abnormalities detected with ultrasound.

Topics: Adolescent; Basketball; Body Height; Case-Control Studies; Cross-Sectional Studies; Electromyography; Humans; Knee; Knee Joint; Male; Pain; Proprioception; Range of Motion, Articular; Torque; Ultrasonography

Minimizing musculo-skeletal damage and fatigue is considered paramount for performance in trail running. Our purposes were to investigate the effects of the foot strike pattern and its variability on (a) muscle activity during a downhill trail run and (b) immediate and delayed neuromuscular fatigue. Twenty-three runners performed a 6.5-km run (1264 m of negative elevation change). Electromyographic activity of lower-limb muscles was recorded continuously. Heel and metatarsal accelerations were recorded to identify the running technique. Peripheral and central fatigue was assessed in knee extensors (KE) and plantar flexors (PF) at Pre-, Post-, and 2 days post downhill run (Post2d). Anterior patterns were associated with (a) higher gastrocnemius lateralis activity and lower tibialis anterior and vastus lateralis activity during the run and (b) larger decreases in KE high-frequency stimulus-evoked torque Post and larger decrements in KE MVC Post2d. High patterns variability during the run was associated with (a) smaller decreases in KE Db100 Post and MVC Post2d and (b) smaller decreases in PF MVC Post and Post2d. Anterior patterns increase the severity of KE peripheral fatigue. However, high foot strike pattern variability during the run reduced acute and delayed neuromuscular fatigue in KE and PF.

Topics: Acceleration; Adult; Biomechanical Phenomena; Electromyography; Foot; Gait; Heel; Humans; Knee; Linear Models; Male; Metatarsal Bones; Muscle Fatigue; Muscle, Skeletal; Pain; Running; Torque

Studies have suggested a compromised postural control in individuals with knee osteoarthritis (OA) evidenced by larger and faster displacement of center of pressure (COP). However, quantification of postural control in the mini-squat posture performed by patients with early knee OA and its relation to muscle strength and self-reported symptoms have not been investigated. The main aim of this cross-sectional, observational, controlled study was to determine whether postural control in the mini-squat posture differs between individuals with early knee OA and a control group (CG) and verify the relation among knee extensor torque (KET) and self-reported physical function, stiffness and pain. Twenty four individuals with knee OA grades I and II (OAG) (mean age: 52.35±5.00) and twenty subjects without knee injuries (CG) (mean age: 51.40±8.07) participated in this study. Participants were assessed in postural control through a force plate (Bertec Mod. USA), which provided information about the anterior-posterior (AP) and medial-lateral (ML) COP displacement during the mini-squat, in isometric, concentric and eccentric knee extensor torque (KET) (90°/s) through an isokinetic dynamometer (BiodexMulti-Joint System3, Biodex Medical Incorporation, New York, NY, USA), and in self-reported symptoms through the WOMAC questionnaire. The main outcomes measured were the AP and ML COP amplitude and velocity of displacement; isometric, concentric, and eccentric KET and self-reported physical function, stiffness and pain. No significant differences were found between groups for postural control (p>0.05). Significant lower eccentric KET (p=0.01) and higher scores for the WOMAC subscales of pain (p=<0.001), stiffness (p=0.001) and physical function (p<0.001) were found for the OAG. Moderate and negative correlations were found between the AP COP amplitude of displacement and physical function (ρ=-0.40, p=0.02). Moderate and negative correlations were observed between the AP COP velocity of displacement and physical function (ρ=0.47, p=0.01) and stiffness (ρ=-0.45, p=0.02). The findings of the present study emphasize the importance of rehabilitation from the early degrees of knee OA to prevent postural instability and the need to include quadriceps muscle strengthening, especially by eccentric contractions. The relationship between the self-reported symptoms and a lower and slower COP displacement suggest that the postural control strategy during tasks with a semi-flexed knee s

Topics: Cross-Sectional Studies; Humans; Isometric Contraction; Knee; Knee Joint; Male; Middle Aged; Movement; Muscle Strength; Muscle, Skeletal; Osteoarthritis, Knee; Pain; Postural Balance; Posture; Quadriceps Muscle; Self Report; Torque

Foot and ankle structures are the most commonly affected in people with gout. However, the effect of gout on foot and ankle muscle strength is not well understood. The primary aim of this study was to determine whether differences exist in foot and ankle muscle strength for plantarflexion, dorsiflexion, inversion and eversion between people with gout and age- and sex-matched controls. The secondary aim was to determine whether foot and ankle muscle strength was correlated with foot pain and disability.. Peak isokinetic concentric muscle torque was measured for ankle plantarflexion, dorsiflexion, eversion and inversion in 20 participants with gout and 20 matched controls at two testing velocities (30°/s and 120°/s) using a Biodex dynamometer. Foot pain and disability was measured using the Manchester Foot Pain and Disability Index (MFPDI).. Participants with gout demonstrated reduced muscle strength at both the 30°/s and 120°/s testing velocities for plantarflexion, inversion and eversion (P<0.05). People with gout also displayed a reduced plantarflexion-to-dorsiflexion strength ratio at both 30°/s and 120°/s (P<0.05). Foot pain and disability was higher in people with gout (P<0.0001) and MFPDI scores were inversely correlated with plantarflexion and inversion muscle strength at the 30°/s testing velocity, and plantarflexion, inversion and eversion muscle strength at the 120°/s testing velocity (all P<0.05).. People with gout have reduced foot and ankle muscle strength and experience greater foot pain and disability compared to controls. Foot and ankle strength reductions are strongly associated with increased foot pain and disability in people with gout.

Topics: Adult; Aged; Ankle; Case-Control Studies; Cross-Sectional Studies; Female; Foot; Gout; Humans; Male; Middle Aged; Muscle Strength; Muscle Strength Dynamometer; Muscle Weakness; Muscle, Skeletal; Pain; Torque

The aim of this study was to assess whether side-to-side differences in morphology and function of the upper limbs in 11-12 year-old male baseball players with throwing-related pain (n=14) were more pronounced than that of age-matched healthy untrained subjects (n=16). Baseball players 1) had played baseball≥4.5 h·wk

Topics: Baseball; Case-Control Studies; Child; Elbow Injuries; Elbow Joint; Humans; Male; Muscle Strength; Muscle Strength Dynamometer; Pain; Pain Measurement; Range of Motion, Articular; Shoulder Injuries; Shoulder Joint; Shoulder Pain; Surveys and Questionnaires; Torque

The purpose of the study was to compare the mechanical power and work generated by able-bodied subjects during functional magnetic stimulation (FMS) vs. functional electrical stimulation (FES) induced ergometer training conditions. Both stimulation methods were applied at a 30 Hz frequency to the quadriceps muscles of 22 healthy able-bodied subjects to induce cycling for 4× four minutes or until exhaustion. FMS was performed via large surface, cooled coils, while FES was applied with a typical stimulation setup used for cycling. Significantly more (p<10(-3)) muscular power was generated by FMS (23.8 ± 9.1W [mean ± SD]) than by FES (11.3 ± 11.3 W). Additionally, significantly more (p<10(-6)) work was produced by FMS than by FES (4.413 ± 2.209 kJ vs. 0.974 ± 1.269 kJ). The increase in the work was paralleled by a significant prolongation of time to cycling failure (181.8 ± 33.4s vs. 87.0 ± 54.0 s, respectively, p<10(-5)). Compared to FES, FMS can produce more intense and longer cycling exercise in able-bodied subjects. The differing dynamic behaviour of FMS and FES in the presented measurement setup might be related to stimulation induced pain and fatigue mechanisms of the neuromuscular system.

Topics: Adult; Bicycling; Electric Stimulation; Ergometry; Exercise; Female; Humans; Linear Models; Magnetic Fields; Male; Pain; Physical Exertion; Quadriceps Muscle; Time Factors; Torque

The aim of this study was to investigate the effect of neuromuscular electrical stimulation burst duty cycle (BDC) and current type (sinusoidal alternating current [sAC] vs. rectangular alternating current [rAC]) on the electrically induced isometric torque (EIT) and discomfort. Pulsed current (PC) stimulation, which corresponds to one pulse rAC, was included in testing.. A repeated-measures design was used. The left quadriceps of 22 healthy subjects (mean ± SD age, 33 ± 8 yrs) were stimulated alternately with sAC and rAC current bursts (4-kHz carrier frequency; 71 bursts per second burst frequency) to produce isometric contractions. A range of BDCs were tested for sAC (7%-50%) and rAC (2%-18%) stimulation at fixed intensities while EIT and discomfort were recorded. BDC presentation order was randomized.. Overall, both current types elicited peak EIT at ∼14% BDC (range, 7%-21%). Significantly more EIT was produced by rAC than by sAC stimulation (P < 0.005). Discomfort increased with BDC and was similar for both current types.. The study confirmed previous findings that conventional sAC stimulation (50% BDC) and pulsed current stimulation (rAC with 2% BDC) used in sports and rehabilitation produce similar EIT levels. However, rAC stimulation at low BDC (7%-18%) was more effective (+35% torque produced with similar discomfort) than pulsed current or conventional sAC.

Topics: Adult; Electric Stimulation Therapy; Female; Humans; Isometric Contraction; Knee Joint; Male; Muscle Strength; Pain; Quadriceps Muscle; Time Factors; Torque

Medial tibial stress syndrome (MTSS) is a common problem among athletes and soldiers. There is no proven theory that could explain the pathophysiology of shin splints. The therapies described so far are time-consuming and involve a high risk of relapse. The method according to the fascial distortion model (FDM) addresses local changes in the area of the lower leg fascia. It is suited to reduce pain and functional impairments associated with this symptom complex by applying targeted manual techniques. 32 patients (male: 30; female: 2) participated in this study. Visual analogue scale (VAS) was used for the quantification of pain. Scores were also given to rate the maximum painless exercise tolerance of the patients. Subsequently treatment of the crural fascia was performed. Patients retested ability of running and jumping. Therapy was continued until full exercise tolerance or painlessness was reached. A significant reduction of the VAS pain score from 5.2 to 1.1 could be achieved (P < 0.001). The impairment of exercise tolerance could be reduced from 7 to 2 points (P < 0.001). The duration of treatment was 6.3 (SD: 4.3) days on average. The FDM therapy is a potential effective method for acute treatment of MTSS.

Topics: Adult; Athletes; Case-Control Studies; Fascia; Female; Humans; Male; Medial Tibial Stress Syndrome; Military Personnel; Musculoskeletal Manipulations; Pain; Pain Management; Pain Measurement; Prospective Studies; Tibia; Torque

The aims of this study were first to compare the response of dominant and non-dominant legs to eccentric exercise and second, to examine whether there is an effect of exercise order on the magnitude of symptoms associated with intense eccentric protocols. Eighteen young men performed three sets of 30 maximal eccentric isokinetic (60° s(-1)) contractions of the knee extensors (range of motion, ROM: 0°-100°, 0 = full extension) using either dominant or non-dominant leg. They repeated a similar eccentric bout using the contralateral leg 6 weeks later. The sequence of leg's use was allocated to create equally balanced groups. Four indirect markers of muscle damage including subjective pain intensity, maximal isometric strength, muscle stiffness and plasma creatine kinase (CK) activity were measured before and 24 h after exercise. All markers changed significantly following the eccentric bout performed either by dominant or non-dominant legs, but no significant difference was observed between legs. Interestingly, the comparison between the first and second eccentric bouts revealed that muscle soreness (-42%, P<0.001), CK activity (-62%, P<0.05) and strength loss (-54%, P<0.01) were significantly lower after the second bout. This study suggests that leg dominance does not influence the magnitude of exercise-induced muscle damage and supports for the first time the existence of a contralateral protection against exercise-induced muscle damage in the lower limbs.

Topics: Adult; Analysis of Variance; Biomarkers; Biomechanical Phenomena; Creatine Kinase; Exercise; Functional Laterality; Humans; Knee Joint; Male; Muscle Contraction; Muscle Strength; Muscle, Skeletal; Muscular Diseases; Pain; Range of Motion, Articular; Time Factors; Torque; Young Adult

Many digital human models provide the crucial method to calculate postures in virtual environments. Traditionally these methods refer to experiments and make use of statistical modeling. They provide sufficient results in their specialized domain, but cannot be used in general applications. In addition they do not consider important design aspects as forces and discomfort. Hence a new force based approach has been introduced in order to overcome these shortcomings. Based on biomechanical models of active maximal and passive receding joint torques, a mechanical optimization generates static stable postures and related discomfort ratings. The results were promising, but showed some model deficiencies and were not validated in detail. The present paper continues this work and provides necessary model enhancements. Finally the new prediction models are validated on real experiments. The validation results are presented and discussed regarding to usability aspects and future development work.

Topics: Biomechanical Phenomena; Computer Simulation; Female; Humans; Male; Models, Biological; Pain; Posture; Torque

Autologous chondrocyte implantation has become an established technique for addressing knee cartilage defects. Despite reported improvement in pain and regeneration of hyaline-like repair tissue, little has been reported on the recovery of knee strength.. Knee strength assessment was undertaken in 60 patients at 5 years following autologous chondrocyte implantation. Using an isokinetic dynamometer, and during isokinetic knee extension and flexion angular velocities of 60°, 90° and 120°/s, the peak torque, torque at 45° of knee flexion and hamstrings/quadriceps ratio was obtained, in both the operated and non-operated limbs. Pain at the time of assessment was obtained. Independent sample t-tests were used to assess differences in the operated and non-operated sides.. There were no significant differences (p>0.05) between the operated and non-operated legs in the peak knee flexor torque or knee flexor torque at a knee flexion angle of 45°, at all angular velocities (60°, 90° and 120°/s). While the peak knee extensor torque was less in the operated leg at all angular velocities, these differences were not significant (p>0.05). However, a significantly reduced (p<0.05) knee extensor torque at a knee flexion angle of 45°, was observed at all speeds.. While patients had recovered their knee flexor strength, they still demonstrated a reduced knee extensor strength profile at 5 years. This demonstrates that the early supervised rehabilitation phase following autologous chondrocyte implantation is not sufficient to restore long-term knee strength, and ongoing patient advice and rehabilitation is required extending beyond this early period. It is unknown how this prolonged reduction in strength may affect long-term graft outcome.

Topics: Adolescent; Adult; Biomechanical Phenomena; Cartilage; Cartilage Diseases; Cell Transplantation; Chondrocytes; Female; Humans; Kinetics; Knee; Knee Joint; Male; Middle Aged; Orthopedic Procedures; Pain; Regeneration; Torque; Transplantation, Autologous

Low-frequency pulsed current (LFPC) and Russian current (RC), a type of kilohertz-frequency alternating current, have been frequently used for muscle strengthening in rehabilitation programs. Despite the popularity of these current types, it is unclear which is most effectively able to generate a similar submaximal torque with minimal discomfort and current amplitude.. To compare discomfort and current amplitude between LFPC and RC to achieve a knee extensor torque of 10% of the maximal isometric voluntary contraction (MIVC).. Twenty-two healthy subjects were subjected to three electrically elicited knee extensor submaximal contractions (10% MIVC) that were sustained for 10 seconds. The current amplitude required to achieve 10% MIVC and subjective discomfort were assessed directly by the electrical stimulator and with the Visual Analogue Pain Scale, respectively. A paired t-test was used to determine differences between the electrical currents (α = 0.05).. LFPC required significantly lower current amplitude (15%) and a lower discomfort level (50%) to achieve 10% of MIVC compared to RC.. LFPC current seems to be more effective than RC with respect to discomfort level and current amplitude to produce 10% of MIVC.

Topics: Adult; Biomechanical Phenomena; Electric Stimulation Therapy; Female; Humans; Isometric Contraction; Knee Joint; Male; Muscle Strength; Muscle, Skeletal; Pain; Pain Measurement; Time Factors; Torque; Treatment Outcome; Young Adult

This study investigated the association between isokinetic peak torque (PT) of quadriceps and the corresponding peak rate of force development (peak RFD) during the recovery of eccentric exercise. Twelve untrained men (aged 21·7 ± 2·3 year) performed 100 maximal eccentric contractions for knee extensors (10 sets of 10 repetitions with a 2-min rest between each set) on isokinetic dynamometer. PT and peak RFD accessed by maximal isokinetic knee concentric contractions at 60° s(-1) were obtained before (baseline) and at 24 and 48 h after eccentric exercise. Indirect markers of muscle damage included delayed onset of muscle soreness (DOMS) and plasma creatine kinase (CK) activity. The eccentric exercise resulted in elevated DOMS and CK compared with baseline values. At 24 h, PT (-15·3%, P = 0·002) and peak RFD (-13·1%, P = 0·03) decreased significantly. At 48 h, PT (-7·9%, P = 0·002) was still decreased but peak RFD have returned to baseline values. Positive correlation was found between PT and peak RFD at baseline (r = 0·62, P = 0·02), 24 h (r = 0·99, P = 0·0001) and 48 h (r = 0·68, P = 0·01) after eccentric exercise. The magnitude of changes (%) in PT and peak RFD from baseline to 24 h (r = 0·68, P = 0·01) and from 24 to 48 h (r = 0·68, P = 0·01) were significantly correlated. It can be concluded that the muscle damage induced by the eccentric exercise affects differently the time course of PT and peak RFD recovery during isokinetic concentric contraction at 60° s(-1). During the recovery from exercise-induced muscle damage, PT and peak RFD are determined but not fully defined by shared putative physiological mechanisms.

Topics: Arthrometry, Articular; Biomarkers; Biomechanical Phenomena; Creatine Kinase; Exercise; Humans; Male; Muscle Contraction; Muscle Fatigue; Muscle Strength; Muscle Strength Dynamometer; Pain; Quadriceps Muscle; Range of Motion, Articular; Recovery of Function; Spectrum Analysis; Time Factors; Torque; Young Adult

Exercise-induced muscle injury is commonly accompanied by a reduction of muscular strength. It has been suggested that this reduction in voluntary force is attributable to "peripheral" and "central" mechanisms within the neuromuscular system. The quadriceps muscle of 15 subjects was damaged with four bouts of 25 maximal voluntary concentric-eccentric contractions at a speed of 60°/s. In a time period of 7 days, we investigated the contribution of agonist muscle activation and contractile properties (CP) to changes in isometric maximum voluntary torque (iMVT). In order to provide a comprehensive assessment, the neural drive to muscles was estimated with the interpolated twitch technique and root mean square of the EMG signal. CP were evaluated by analysing the twitch torque signal induced by single and doublet stimulation. Furthermore, we measured changes in alpha motoneuron excitability of vastus medialis at the spinal level due to muscle soreness using the H reflex technique. The iMVT was impaired at post, 24 h and 48 h, while rate of torque development and voluntary activation (VA) were only decreased immediately after the intervention. CP were impaired immediately after exercise and at 24 h. Maximal H reflex (Hmax), maximal M wave (Mmax) and the Hmax/Mmax-ratio were not affected. Sensation of muscle soreness assessment revealed impairments at 24 h, 48 h and 72 h. Data suggest that reduced VA and altered CP contribute to the force loss immediately after concentric-eccentric exercise. Thereafter, the impairment of CP seems to be mainly responsible for the reduced iMVT. In addition, there is no evidence for an association between muscle soreness and VA as well as between muscle soreness and spinal excitability.

Topics: Adult; Electric Stimulation; Electromyography; Exercise; Female; Humans; Male; Muscle Contraction; Muscle, Skeletal; Pain; Quadriceps Muscle; Torque

The aim of this study was to test the hypothesis that the repeated bout effect depends on intraindividual variability during a second bout of eccentric exercise. Eleven healthy men performed 2 resistance training bouts consisting of maximal eccentric exercise (EE1 and EE2) using the knee extensor muscles. The interval between the exercise bouts was 2 weeks and consisted of 10 sets of 12 repetitions at 160° · s(-1). Maximal isokinetic concentric torque at 30° · s(-1) was measured before the bouts and 2 minutes and 24 hours thereafter. Muscle soreness score and creatine kinase activity were determined before and after exercise. Intraindividual variability in torque during each eccentric repetition was measured during exercise. Repeated bout effect manifested after EE2: Muscle soreness was less, the shift in optimal knee joint angle to a longer muscle length was less, and the decrease in isokinetic concentric torque 2 minutes after exercise was less for EE2 compared with that for EE1. During concentric (isokinetic) contraction, length-dependent changes in isokinetic torque (IT) occurred after both EE1 and EE2: The shorter the muscle length, the greater the change in IT. There was a significant relationship between the decrease in maximal isokinetic knee extension torque 24 hours after EE1 and intraindividual variability of EE1 (R2 = 0.71, p < 0.05), but this relationship was not significant for EE2 (R2 = 0.18). It seems that intraindividual variability during eccentric exercise protects against muscle fatigue and damage during the first exercise bout but not during a repeat bout. These findings may be useful to coaches who wish to improve muscle function in resistance training with less depression in muscle function and discomfort of their athletes, specifically, when muscle is most sensitive to muscle-damaging exercise.

Topics: Adaptation, Physiological; Adult; Creatine Kinase; Exercise; Humans; Knee; Male; Muscle Contraction; Muscle Fatigue; Muscle, Skeletal; Pain; Resistance Training; Torque; Young Adult

It was recently demonstrated that musculoarticular (MA) stiffness is related to sprint cycling performance in nonfatigued conditions. This study examined whether relatively stiffer cyclists were more effective at sprinting under fatigued conditions, as occurs during endurance cycling competitions.. MA stiffness of the quadriceps was assessed in 21 trained male cyclists (28.7 ± 9.5 yr, 1.74 ± 0.08 m, 67.5 ± 7.2 kg). Participants also performed a maximal 6-s sprint on a cycle ergometer to assess peak power output (POpeak), peak crank torque (CTpeak), and peak rate of crank torque development (RCTDpeak). A cycling fatigue protocol then required cyclists to pedal at 30%, 35%, and 40% of POpeak and sprint at the end of each stage. Surface EMG was recorded from vastus lateralis during each sprint and analyzed in the time domain as integrated EMG (iEMG) and in the frequency domain as instantaneous median frequency (MDF) adopting a continuous wavelet transform. Participants were then retested for MA stiffness.. MA stiffness (-12%) was significantly reduced after the cycling protocol. Further, POpeak, CTpeak, RCTDpeak, and iEMG were reduced by 20%, 15%, 13%, and 20%, respectively, after the fatigue protocol (P<0.05). When the cyclists were divided into relatively stiff (SG) and relatively compliant groups (CG), only SG exhibited significant decreases in MA stiffness, CTpeak, RCTDpeak (P<0.05), and instantaneous MDF (R=0.705).. Whereas neuromechanical parameters were generally reduced under conditions of fatigue, stiff and compliant cyclists were affected differently, with the sprint abilities of SG decreased to the level of CG. It seems important for endurance cyclists to incorporate training strategies to maintain MA stiffness during competition to offset declines in sprint performance.

Topics: Adult; Bicycling; Electromyography; Exercise Test; Humans; Isometric Contraction; Male; Muscle Fatigue; Muscle, Skeletal; Pain; Running; Torque; Young Adult

The aim of this study was to investigate the differences in the length-dependent changes in quadriceps muscle torque during voluntary isometric and isokinetic contractions performed after severe muscle-damaging exercise. Thirteen physically active men (age = 23.8 ± 3.2 years, body weight = 77.2 ± 4.5 kg) performed stretch-shortening cycle (SSC) exercise comprising 100 drop jumps with 30-second intervals between each jump. Changes in the voluntary and electrically evoked torque in concentric and isometric conditions at different muscle lengths, muscle soreness, and plasma creatine kinase (CK) activity were assessed within 72 hours after SSC exercise. Isokinetic knee extension torque decreased significantly (p < 0.05) at all joint angles after SSC exercise. At 2 minutes and at 72 hours after SSC exercise, the changes in knee torque were significantly smaller at 80° (where 180° = full knee extension) than at 110-130°. At 2 minutes after SSC exercise, the optimal angle for isokinetic knee extension torque shifted by 9.5 ± 8.9° to a longer muscle length (p < 0.05). Electrically induced torque at low-frequency (20-Hz) stimulation decreased significantly more at a knee joint angle of 130° than at 90°. The subjects felt acute muscle pain and CK activity in the blood increased to 1,593.9 ± 536.2 IU·L⁻¹ within 72 hours after SSC exercise (p < 0.05). This study demonstrates that the effect of muscle-damaging exercise on isokinetic torque is greatest for contractions at short muscle lengths. These findings have practical importance because the movements in most physical activities are dynamic in nature, and the decrease in torque at various points in the range of motion during exercise might affect overall performance.

Topics: Adult; Cohort Studies; Electric Stimulation; Electromyography; Exercise; Humans; Isometric Contraction; Male; Muscle Fatigue; Muscle Stretching Exercises; Pain; Quadriceps Muscle; Risk Assessment; Time Factors; Torque; Young Adult

We used ³¹P-magnetic resonance spectroscopy to test the hypothesis that exercise-induced muscle damage (EIMD) alters the muscle metabolic response to dynamic exercise, and that this contributes to the observed reduction in exercise tolerance following EIMD in humans. Ten healthy, physically active men performed incremental knee extensor exercise inside the bore of a whole body 1.5-T superconducting magnet before (pre) and 48 h after (post) performing 100 squats with a load corresponding to 70% of body mass. There were significant changes in all markers of muscle damage [perceived muscle soreness, creatine kinase activity (434% increase at 24 h), and isokinetic peak torque (16% decrease at 24 h)] following eccentric exercise. Muscle phosphocreatine concentration ([PCr]) and pH values during incremental exercise were not different pre- and post-EIMD (P > 0.05). However, resting inorganic phosphate concentration ([P(i)]; pre: 4.7 ± 0.8; post: 6.7 ± 1.7 mM; P < 0.01) and, consequently, [P(i)]/[PCr] values (pre: 0.12 ± 0.02; post: 0.18 ± 0.05; P < 0.01) were significantly elevated following EIMD. These mean differences were maintained during incremental exercise (P < 0.05). Time to exhaustion was significantly reduced following EIMD (519 ± 56 and 459 ± 63 s, pre- and post-EIMD, respectively, P < 0.001). End-exercise pH (pre: 6.75 ± 0.04; post: 6.83 ± 0.04; P < 0.05) and [PCr] (pre: 7.2 ± 1.7; post: 14.5 ± 2.1 mM; P < 0.01) were higher, but end-exercise [P(i)] was not significantly different (pre: 19.7 ± 1.9; post: 21.1 ± 2.6 mM, P > 0.05) following EIMD. The results indicate that alterations in phosphate metabolism, specifically the elevated [P(i)] at rest and throughout exercise, may contribute to the reduced exercise tolerance observed following EIMD.

Topics: Adolescent; Adult; Analysis of Variance; Biomarkers; Biomechanical Phenomena; Creatine Kinase, MM Form; Energy Metabolism; Exercise; Exercise Tolerance; Humans; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Male; Muscle Contraction; Muscle Fatigue; Muscle, Skeletal; Muscular Diseases; Pain; Pain Measurement; Phosphates; Phosphocreatine; Phosphorus Isotopes; Time Factors; Torque; Young Adult

Maximal isometric quadriceps strength deficits have been widely reported in studies of knee osteoarthritis (OA), however little is known about the effect of osteoarthritis knee pain on submaximal quadriceps neuromuscular function. The purpose of this study was to measure vastus medialis motor unit (MU) properties in participants with knee OA, during submaximal isometric contractions.. Vastus medialis motor unit potential (MUP) parameters were assessed in 8 patients with knee OA and 8 healthy, sex and age-matched controls during submaximal isometric contractions (20% of maximum isometric torque). Unpaired t-tests were used to compare groups for demographic and muscle parameters.. Maximum knee extension torque was ~22% lower in the OA group, a difference that was not statistically significantly (p = 0.11). During submaximal contractions, size related parameters of the needle MUPs (e.g. negative peak duration and amplitude-to-area ratio) were greater in the OA group (p < 0.05), with a rightward shift in the frequency distribution of surface MUP negative peak amplitude. MUP firing rates were significantly lower in the OA group (p < 0.05).. Changes in MU recruitment and rate coding strategies in OA may reflect a chronic reinnervation process or a compensatory strategy in the presence of chronic knee pain associated with OA.

Topics: Action Potentials; Electromyography; Female; Humans; Isometric Contraction; Knee Joint; Male; Middle Aged; Motor Neurons; Neural Conduction; Osteoarthritis, Knee; Pain; Quadriceps Muscle; Range of Motion, Articular; Recruitment, Neurophysiological; Torque

The aim of this study was to investigate the mechanical power of the ankle plantar flexion. The investigated power of the ankle plantar flexion would help to improve effectively the FES walking system using the ankle plantar flexion for patients and aged people in slow walking. The subjective pain by electrical stimulation sometimes becomes the burden to use the FES system. We also investigated the relationship between the mechanical power in ankle plantar flexion by electrical stimulation and the subjective pain. We developed the device to measure the ankle movement by electrical stimulation against load resistance torque. The device consisted of pads to support a single lower leg, a rotational footplate with a large pulley and a vertical weight to generate the load resistance torque, and a monophasic electrical stimulator via surface electrodes. Our results showed the proportional relationship between the mechanical power of the ankle plantar flexion and the subjective pain by electrical stimulation. To generate the same level in the ankle plantar flexor power 2.75 W under the maximum voluntary exertion, the subjective pain by electrical stimulation exceeded 70, which means the feeling of crying at the Face Pain Scale. This result would help the better design of the FES walking system using the ankle plantar flexion for patients and aged people.

Topics: Adult; Aged; Ankle; Ankle Joint; Biomechanical Phenomena; Electric Stimulation; Electric Stimulation Therapy; Electrodes; Equipment Design; Gait; Humans; Male; Pain; Stress, Mechanical; Time Factors; Torque; Walking

An increase to above-baseline levels of electromyography (EMG) mean power spectral frequency (MPF) has been observed previously during muscle recovery following fatiguing contractions and has been explained by membrane hyperpolarization due to increased activation of the Na+-K+ pump. It is hypothesized that this membrane mechanism is impaired by muscle fiber damage following eccentric exercise. Thus, the aim of the study was to investigate surface EMG signal characteristics during recovery from fatigue after eccentric exercise. Ten healthy subjects performed sustained isometric knee extensions at 40% of the maximal torque (MVC) until task failure before, immediately after and 24 and 48 h after eccentric exercise. Bipolar surface EMG signals were recorded from six locations over the quadriceps during the sustained isometric contraction and during 3-s long contractions at 40% MVC separated by 1-min intervals for 15 min (recovery). Before the eccentric exercise, MPF of EMG signals increased to values above baseline during recovery from the fatiguing isometric contraction (P<0.001), whereas immediately after and 24 and 48 h after the eccentric task, MPF was lower than baseline during the entire recovery period (P<0.01). In conclusion, delayed-onset muscle soreness abolished the supranormal increase in EMG MPF following recovery from fatigue.

Topics: Adult; Electromyography; Humans; Isometric Contraction; Male; Muscle, Skeletal; Pain; Quadriceps Muscle; Skin Temperature; Time Factors; Torque; Young Adult

Women are often reported to be generally more resistant to fatigue than men for relative-intensity tasks. This has been observed repeatedly for elbow flexors, whereas at the ankle, sex differences appear less robust, suggesting localized rather than systemic influences. Thus, the purpose of this study was to examine sex differences in fatigue resistance at muscle groups in a single cohort and which factors, if any, predict endurance time.. Thirty-two young adults (age = 19-44 yr, 16 women) performed sustained isometric contractions at 50% maximum voluntary isometric contraction to failure for elbow flexion and ankle dorsiflexion. Pain, exertion, and muscle EMG were assessed throughout. Self-reported baseline activity was measured using the International Physical Activity Questionnaire.. Women were significantly more resistant to fatigue than men at the elbow (112.3 ± 6.2 vs 80.3 ± 5.8 s, P = 0.001) but not at the ankle (140.6 ± 10.7 vs 129.2 ± 10.5 s, P = 0.45). Peak torque was greater in men than that in women (P < 0.0001) at the ankle (45.0 ± 1.7 vs 30.1 ± 1.0 N·m) and at the elbow (75.7 ± 3.1 vs 34.4 ± 2.2 N·m). Peak torque was significantly related to endurance time at the elbow (R2= 0.30) but not at the ankle (R2 = 0.03). Peak pain, rate of pain increase, peak exertion, EMG, and baseline physical activity did not differ between sexes.. Sex differences in fatigue resistance are muscle group specific. Women were more fatigue resistant at the elbow but not at the ankle during a sustained isometric contraction. Further, factors that may contribute to fatigue resistance for one muscle group (e.g., sex, peak torque) may not be critical at another.

Topics: Adult; Ankle; Cohort Studies; Elbow; Female; Humans; Isometric Contraction; Male; Motor Activity; Muscle Fatigue; Muscle, Skeletal; Pain; Physical Endurance; Sex Factors; Torque; Young Adult

Skeletal muscle damage frequently occurs after eccentric exercise, however, the relationship between intraindividual variability of eccentric exercise and skeletal muscle damage is not clear yet. The aim of the study was to test the hypothesis that prolonged decrease in skeletal muscle force depends on intraindividual variability of eccentric exercise. Eleven healthy men were asked to perform knee eccentric extension of 10 series with 12 repetitions (EE) with maximal intensity at 160 degrees/s. The maximal voluntary knee extension isometric torque (MVC) of the quadriceps muscle and isokinetic concentric torque (IT) at 30 degrees/s of knee angles were established before and 2 min, 60 min, 24 h and 14 days after EE. At 24 h and 48 h after EE muscle soreness and creatine kinase activity before and at 48 h after EE were calculated. The intraindividual variability of EE and autocorrelation coefficient of EE were calculated. We observed a significant decrease in MVC and IT after EE. The maximal isokinetic torque shifted to longer muscle length after EE. It was concluded that longer lasting (within 14 days) indirect symptoms of exercise induced muscle damage (decrease in muscle force) are closely related to variability of EE.

Topics: Adult; Creatine Kinase; Exercise; Humans; Knee; Male; Muscle Fatigue; Muscle, Skeletal; Pain; Torque; Young Adult

Using "painless" magnetic stimulation (FMS) to support the cycling of paretic subjects with preserved sensation is possible and potentially superior to electrical stimulation (FES). We investigated the dependence of the torque and the pain evoked by FMS and FES on stimulation conditions in order to optimize magnetic stimulation.. Torque and pain induced by quadriceps stimulation in 13 subjects with paresis and preserved sensation (due to multiple sclerosis) were compared under the conditions: (1) small vs large stimulated surfaces of the thigh, (2) varying contraction velocities of the muscle (isometric vs 15 and 30 rpm isokinetic speed), (3) FMS vs FES modalities, and (4) varying magnetic coil locations.. Torque and pain significantly depended on the amount of surface and location of stimulation during FMS, on the stimulation modality, and on the muscle contraction velocity during FES and FMS. FMS with a saddle-shaped coil produced more torque (p<0.05) than any other stimulation modality, even at 30 rpm velocity.. To support leg cycling of subjects with preserved sensation, the application of FMS stimulation with a large-surface saddle-shaped coil and the focusing of stimulation on the lateral-frontal surface of the thigh produces greater torque and less pain than FES.. Optimized magnetic stimulation is a superior alternative to electrical stimulation in the rehabilitation of subjects with preserved sensation.

Topics: Adult; Disease Progression; Electric Stimulation; Electromyography; Female; Humans; Isometric Contraction; Magnetic Field Therapy; Magnetic Resonance Imaging; Male; Middle Aged; Multiple Sclerosis; Muscle, Skeletal; Pain; Paresis; Spinal Cord Injuries; Thigh; Torque

Eccentric contractions (ECC) require lower systemic oxygen (O2) and induce greater symptoms of muscle damage than concentric contractions (CON); however, it is not known if local muscle oxygenation is lower in ECC than CON during and following exercise. This study compared between ECC and CON for changes in biceps brachii muscle oxygenation [tissue oxygenation index (TOI)] and hemodynamics [total hemoglobin volume (tHb)=oxygenated-Hb+deoxygenated-Hb], determined by near-infrared spectroscopy over 10 sets of 6 maximal contractions of the elbow flexors of 10 healthy subjects. This study also compared between ECC and CON for changes in TOI and tHb during a 10-s sustained and 30-repeated maximal isometric contraction (MVC) task measured immediately before and after and 1-3 days following exercise. The torque integral during ECC was greater (P<0.05) than that during CON by approximately 30%, and the decrease in TOI was smaller (P<0.05) by approximately 50% during ECC than CON. Increases in tHb during the relaxation phases were smaller (P<0.05) by approximately 100% for ECC than CON; however, the decreases in tHb during the contraction phases were not significantly different between sessions. These results suggest that ECC utilizes a lower muscle O2 relative to O2 supply compared with CON. Following exercise, greater (P<0.05) decreases in MVC strength and increases in plasma creatine kinase activity and muscle soreness were evident 1-3 days after ECC than CON. Torque integral, TOI, and tHb during the sustained and repeated MVC tasks decreased (P<0.01) only after ECC, suggesting that muscle O2 demand relative to O2 supply during the isometric tasks was decreased after ECC. This could mainly be due to a lower maximal muscle mass activated as a consequence of muscle damage; however, an increase in O2 supply due to microcirculation dysfunction and/or inflammatory vasodilatory responses after ECC is recognized.

Topics: Adult; Creatine Kinase; Cross-Over Studies; Female; Hemodynamics; Hemoglobins; Humans; Isometric Contraction; Male; Muscle, Skeletal; Oxygen; Oxygen Consumption; Oxyhemoglobins; Pain; Pain Measurement; Spectroscopy, Near-Infrared; Time Factors; Torque; Upper Extremity; Young Adult

To compare the strength of the hip musculature in people with symptomatic medial knee osteoarthritis (OA) with asymptomatic controls.. Eighty-nine people with knee OA and 23 controls age >50 years were recruited from the community. The maximal isometric strength (torque relative to body mass) of the hip abductors, adductors, flexors, extensors, and internal and external rotators was evaluated using hand-held dynamometry or a customized force transducer apparatus. Univariate linear models with age and sex included as covariates were used to compare muscle strength between groups.. In people with knee OA, significant strength deficits were evident for all hip muscle groups evaluated (P < 0.05). Compared with controls, strength deficits ranged from 16% (hip extensors) to 27% (hip external rotators) after accounting for differences in sex and age between groups.. People with knee OA demonstrate significant weakness of the hip musculature compared with asymptomatic controls. It is not clear if hip muscle weakness precedes the onset of knee OA or occurs as a consequence of disease. Findings from this study support the inclusion of hip strengthening exercises in rehabilitation programs.

Topics: Aged; Case-Control Studies; Exercise; Exercise Therapy; Female; Hip; Humans; Male; Middle Aged; Muscle Strength; Muscle Weakness; Osteoarthritis, Knee; Pain; Torque

To evaluate the difference in isokinetic strength of hip muscles between patients with knee osteoarthritis (OA) and matched healthy controls, and to establish the correlation between this isokinetic strength and pain and function in patients with knee OA.. 25 patients with a diagnosis of unilateral knee OA, 25 patients with bilateral knee OA, and 50 matched controls were evaluated using the visual analog scale for pain, knee Lequesne index, Western Ontario and McMaster Universities questionnaire and an isokinetic test.. The groups were matched for age, gender and body mass index. The results of the isokinetic test revealed lower peak torque of the hip in patients with OA of the knee than in the control group for all movements studied. Strong correlations were found between the peak torque, visual analog scale and function.. Patients with OA of the knee exhibit lower isokinetic strength in the hip muscles than healthy control subjects. Strengthening the muscles surrounding the hip joint may help to decrease pain in people with knee OA. Some correlations between pain/function and peak torque were found.

Topics: Adult; Body Mass Index; Case-Control Studies; Exercise Test; Female; Hip; Humans; Male; Middle Aged; Muscle Strength; Muscle, Skeletal; Osteoarthritis, Knee; Pain; Torque

The study measured the effect of stretch on passive mechanical properties in unexercised and eccentrically exercised plantarflexor muscles, to obtain insight into how stretch might serve athletes as a warm-up strategy. Passive torque, voluntary contraction strength and muscle soreness were measured before and after a large amplitude stretch given before and after a period of eccentric exercise and at 0, 1, 2 and 24 h later. Stretch of the unexercised muscle led to a 20% fall in passive torque which recovered within an hour. About 40% of the fall could be recovered immediately with a voluntary contraction. After eccentric exercise there was a rise in passive torque by 20% at 2 h post-exercise. This rise was postulated to result from an injury contracture in muscle fibres damaged by the exercise. It was accompanied by a fall in maximum voluntary torque and the development of muscle soreness at 24 h. Stretch of the exercised muscle led to a fall in passive torque and rise in pain threshold. It is proposed that in response to a stretch there is a fall in passive tension in the muscle due to stable cross-bridges in sarcomeres which could be recovered with a voluntary contraction and an additional component attributable to the elastic filament, titin. The size of the fall was not significantly different between exercised and unexercised muscle. These observations provide a physiological basis for the effects of passive stretches on skeletal muscle and help to explain why they are used as a popular warm-up strategy.

Topics: Analysis of Variance; Ankle; Electromyography; Female; Humans; Male; Muscle Contraction; Muscle Strength; Muscle Stretching Exercises; Muscle Tonus; Muscle, Skeletal; Pain; Pain Measurement; Pain Threshold; Torque; Young Adult

Twenty-seven right-handed male university students participated in this study, which comprised a full factorial model consisting of three forearm rotation angles (60% prone and supine and neutral range of motion), three elbow angles (45 degrees , 90 degrees and 135 degrees ), three upper arm angles (45 degrees flexion/extension and neutral), one exertion frequency (15 per min) and one level of pronation torque (20% maximum voluntary contraction (MVC) relative to MVC at each articulation). Discomfort rating after the end of each 5 min treatment was recorded on a visual analogue scale. Results of a repeated measures analysis of covariance on discomfort score, with torque endurance time as covariate, indicated that none of the factors was significant including torque endurance time (p = 0.153). An initial data collection phase preceded the main experiment in order to ensure that participants exerted exactly 20% MVC of the particular articulation. In this phase MVC pronation torque was measured at each articulation. The data revealed a significant forearm rotation angle effect (p = 0.001) and participant effect (p = 0.001). Of the two-way interactions, elbow*participant (p = 0.004), forearm*participant (p = 0.001) and upper arm*participant (p = 0.005) were the significant factors. Electromyographic activity of the pronator teres and biceps brachii muscles revealed no significant change in muscle activity in most of the articulations. Industrial jobs involving deviated upper arm postures are typical in industry but have a strong association with injury. Data from this study will enable better understanding of the effects of deviated upper arm postures on musculoskeletal disorders and can also be used to identify and control high-risk tasks in industry.

Topics: Adult; Analysis of Variance; Arm Injuries; Arthrometry, Articular; Biomechanical Phenomena; Electromyography; Forearm; Humans; Isometric Contraction; Male; Muscle, Skeletal; Pain; Pain Measurement; Posture; Shoulder Injuries; Shoulder Joint; Students; Supination; Time Factors; Torque; Universities

Eccentric muscle actions cause muscle damage and lead to delayed-onset muscle soreness (DOMS), which may impair performance. The purpose of this study was to examine the effect of DOMS on elbow flexion strength and rate of velocity development (RVD). Nineteen college male subjects performed 6 tests (pre- and posteccentric and every 24 hours for 4 days). In the preeccentric tests, each subject reported his arm pain and then did 5 concentric repetitions of elbow flexion/extension on an isokinetic dynamometer at 240 degrees x s(-1). Each subject then completed 6 sets of 10 eccentric elbow flexion actions at 30 degrees x s(-1) and finished with a posteccentric test with another 5 concentric repetitions at 240 degrees x s(-1). On days 1-4, each subject reported his arm pain and then did 5 more repetitions at 240 degrees x s(-1). Analysis was performed on the values for DOMS, peak torque (PT), and RVD. For DOMS, scores on the posteccentric test (2.34 +/- 2.53), day 1 (3.18 +/- 2.18), day 2 (3.21 +/- 2.91), day 3 (1.81 +/- 1.78), and day 4 (1.02 +/- 1.30) were all significantly (p < 0.05) greater than the preeccentric scores (0.00 +/- 0.00). For PT, the scores on the posteccentric test (22.40 +/- 8.87 ft x lb(-1)) and day 1 (23.88 +/- 9.00 ft x lb(-1)) were both significantly less than on the preeccentric test (29.56 +/- 8.42 ft x lb(-1)). The RVD scores on the posteccentric test (1505.73 +/- 462.12 d x s(-1) x s(-1)), day 1 (1571.55 +/- 475.99 d x s(-1) x s(-1)), and day 2 (1546.99 +/- 494.52 d x s(-1) x s(-1)) were all significantly less than on the preeccentric test (1719.86 +/- 473.18 d x s(-1) x s(-1)). This suggests that muscle damage may cause significant decreases in elbow flexion concentric strength and RVD even as DOMS remains elevated.

Topics: Analysis of Variance; Elbow Joint; Exercise; Humans; Male; Muscle Strength; Muscle, Skeletal; Pain; Pain Measurement; Torque; Young Adult

This study compared two training regimens in which knee extensor exercises were performed at different range of motion.. Sixteen males performed bouts of 90 maximal isokinetic eccentric contractions over 6 consecutive days (B1-B6) at either small (n=8) or large (n=8) range of motion. Average of peak torque (Mp) of each of the 90 contraction trials were calculated, plasma creatine kinase (CK) and lactate dehydrogenase (LDH) activities were measured before, 24 h, 48 h and 6 d after B1. Muscle soreness was evaluated every day during the experiment.. At B3 Mp reduced more in group L than in group S. From B1 to B6 group S increased Mp, while in group L Mp did not return to the baseline level. In both groups CK activity elevated 24 h following B1. CK activity was significantly higher in group L 6d after B1. In group L muscle soreness was higher at 48 h, 72 h, 4 d and 5 d after B1.. High-intensity, consecutive eccentric knee extensor exercise training at large range of motion may induce greater development of muscle damage and force deficit, than training at small range of motion. Training at small range of motion may induce early adaptation in voluntary torque production.

Topics: Adaptation, Physiological; Adolescent; Adult; Biomarkers; Biomechanical Phenomena; Creatine Kinase; Exercise; Humans; Knee Joint; L-Lactate Dehydrogenase; Male; Muscle Contraction; Muscular Diseases; Pain; Quadriceps Muscle; Range of Motion, Articular; Recovery of Function; Time Factors; Torque; Young Adult

This study compared resistance-trained and untrained men for changes in commonly used indirect markers of muscle damage after maximal voluntary eccentric exercise of the elbow flexors. Fifteen trained men (28.2 +/- 1.9 years, 175.0 +/- 1.6 cm, and 77.6 +/- 1.9 kg) who had resistance trained for at least 3 sessions per week incorporating exercises involving the elbow flexor musculature for an average of 7.7 +/- 1.4 years, and 15 untrained men (30.0 +/- 1.5 years, 169.8 +/- 7.4 cm, and 79.9 +/- 4.4 kg) who had not performed any resistance training for at least 1 year, were recruited for this study. All subjects performed 10 sets of 6 maximal voluntary eccentric actions of the elbow flexors of one arm against the lever arm of an isokinetic dynamometer moving at a constant velocity of 90 degrees .s. Changes in maximal voluntary isometric and isokinetic torque, range of motion, upper arm circumference, plasma creatine kinase activity, and muscle soreness before, immediately after, and for 5 days after exercise were compared between groups. The trained group showed significantly (P < 0.05) smaller changes in all of the measures except for muscle soreness and faster recovery of muscle function compared with the untrained group. For example, muscle strength of the trained group recovered to the baseline by 3 days after exercise, where the untrained group showed approximately 40% lower strength than baseline. These results suggest that resistance-trained men are less susceptible to muscle damage induced by maximal eccentric exercise than untrained subjects.

Topics: Adult; Creatine Kinase; Elbow Joint; Humans; Male; Muscle Contraction; Muscle Strength; Muscle Strength Dynamometer; Muscle, Skeletal; Pain; Range of Motion, Articular; Torque; Upper Extremity; Weight Lifting

The aim of this study was to investigate whether (1) spinal modulation would change after non-exhausting eccentric exercise of the plantar flexor muscles that produced muscle soreness and (2) central modulation of the motor command would be linked to the development of muscle soreness. Ten healthy subjects volunteered to perform a single bout of backward downhill walking exercise (duration 30 min, velocity 1 ms(-1), negative grade -25%, load 12% of body weight). Neuromuscular test sessions [H-reflex, M-wave, maximal voluntary torque (MVT)] were performed before, immediately after, as well as 1-3 days after the exercise bout. Immediately after exercise there was a -15% decrease in MVT of the plantar flexors partly attributable to an alteration in contractile properties (-23% in electrically evoked mechanical twitch). However, MVT failed to recover before the third day whereas the contractile properties had significantly recovered within the first day. This delayed recovery of MVT was likely related to a decrement in voluntary muscle drive. The decrease in voluntary activation occurred in the absence of any variation in spinal modulation estimated from the H-reflex. Our findings suggest the development of a supraspinal modulation perhaps linked to the presence of muscle soreness.

Topics: Adult; Evoked Potentials, Motor; Exercise; Female; H-Reflex; Humans; Male; Motor Neurons; Muscle Contraction; Muscle Fatigue; Muscle, Skeletal; Pain; Spinal Cord; Torque; Volition; Walking

Activation of nociceptive afferents decreases motor unit discharge rates in static contractions. There is also evidence that during experimental muscle pain the motor unit twitch force increases, which has been hypothesized to compensate for the decrease in discharge rate to maintain constant force. This study examined whether there is an association between the magnitude of change in motor unit discharge rate and the amount of increase in the spike-triggered average torque during experimental muscle pain.. Sixteen subjects performed three constant-torque isometric ankle dorsi-flexions at 10% of the maximal force (MVC) alternated with two contractions at constant discharge rate of a target motor unit, before and following injection of 0.5 ml of hypertonic (painful) or isotonic (control) saline into the tibialis anterior muscle.. The discharge rate of the target unit at 10% MVC decreased following injection of hypertonic saline (P<0.05; mean+/-SD, before: 9.9+/-1.3 pulses per second, pps; after injection: 8.9+/-1.0 pps). The peak of the spike-triggered average torque increased with pain (P<0.05; before: 0.56+/-0.55 mNm; during pain: 0.95+/-1.02 mNm) but the increase was not correlated with the decrease in discharge rate (R=0.08). Propagation velocity and action potential peak-to-peak amplitude did not change with pain.. The pain-induced modifications in the estimated motor unit twitch torque (1) were not caused by changes in muscle fiber action potential, and (2) were not associated with the decrease in discharge rate.. Maintenance of constant force during static painful contractions is not explained by a matching between changes in contractile and control motor unit properties.

Topics: Action Potentials; Adult; Analysis of Variance; Differential Threshold; Electromyography; Female; Humans; Male; Motor Neurons; Muscle Contraction; Muscle, Skeletal; Neural Conduction; Pain; Pain Measurement; Saline Solution, Hypertonic; Torque

Animal models implicate multiple mechanical factors in the initiation of exercise-induced muscle injury. Muscle injury has been widely studied in humans, but few data exist regarding the underlying cause of muscle injury. This study sought to examine the role of torque per active muscle volume in muscle injury. Eight subjects performed 80 electrically stimulated [via electromyostimulation (EMS)] eccentric contractions of the right and left quadriceps femoris (QF) through an 80 degrees arc at 120 degrees /s. Specific torque was varied by applying 25-Hz EMS to one thigh and 100-Hz EMS to the contralateral thigh. Transverse relaxation time (T2) magnetic resonance images of the QF were collected before and 3 days after the eccentric exercise bouts. Injury was assessed via changes in isometric force and ratings of soreness over the course of 14 days after exercise and by determining changes in T2 and muscle volume 3 days after exercise. The 100-Hz EMS induced greater force loss (P < 0. 05), soreness (P < 0.05), change in muscle volume (P = 0.03), and volume of muscle demonstrating increased T2 (P = 0.005) than the 25-Hz EMS. In addition, injury was found to be similar across the QF in all but the most proximal regions of the QF. Our findings suggest that, in humans, high torque per active volume during lengthening muscle contractions is related to muscle injury.

Topics: Adult; Electric Stimulation; Exercise; Female; Humans; Isometric Contraction; Magnetic Resonance Imaging; Male; Muscle Strength; Pain; Pain Measurement; Quadriceps Muscle; Random Allocation; Time Factors; Torque

Neuromuscular electrical stimulation (NMES) involves the use of electrical current to facilitate contraction of skeletal muscle. However, little is known concerning the effects of varying stimulation parameters on muscle function in humans. The purpose of this study was to determine the extent to which varying pulse duration and frequency altered torque production and fatigability of human skeletal muscle in vivo. Ten subjects underwent NMES-elicited contractions of varying pulse frequencies and durations as well as fatigue tests using stimulation trains of equal total charge, yet differing parametric settings at a constant voltage. Total charge was a strong predictor of torque production, and pulse trains with equal total charge elicited identical torque output. Despite similar torque output, higher- frequency trains caused greater fatigue. These data demonstrate the ability to predictably control torque output by simultaneously controlling pulse frequency and duration and suggest the need to minimize stimulation frequency to control fatigue.

Topics: Action Potentials; Adult; Electric Stimulation Therapy; Humans; Muscle Contraction; Muscle Fatigue; Muscle, Skeletal; Muscular Diseases; Pain; Pain Measurement; Pain Threshold; Time Factors; Torque

The purpose of this study was to investigate the force and electromyographic (EMG) signal recorded from the muscles immediately after a sustained fatiguing contraction with or without muscle pain. Ten subjects performed sustained dorsi- and plantarflexions at two contraction levels (50 and 80% of maximum voluntary contraction) until exhaustion with or without muscle pain induced by injection of 6% hypertonic saline in one of the torque producing muscles. The muscle pain intensity was scored on a visual analogue scale (VAS, 0-10 cm). The root mean square (RMS) of the surface EMG signal from plantarflexors and dorsiflexors were estimated during maximum voluntary contractions (MVC) and ramp contractions before and after the fatiguing task at 0, 5, 10 and 15 min during the recovery phase. VAS scores immediately after the contractions with hypertonic saline (on average 3.2 +/- 1.1 cm) progressively decreased during recovery and no pain was experienced 15 min after the contraction. After the painful contraction the RMS-EMG during MVC was on average decreased (23.4 +/- 7.4%) compared to the non-painful condition both in muscles where pain was previously induced and in non-painful synergists. During recovery, the slope of the torque-EMG curve during ramp contraction was significantly decreased (28.4 +/- 8.1%) after the painful contraction compared to the control contraction both for the muscle previously exposed to pain and also the other active synergists. The decreased EMG during recovery after painful contractions compared with control was not accompanied by significant reductions in force during MVC indicating a change in the strategy for motor unit recruitment. This study shows that localized muscle pain inhibits muscle activation and increases the effects of fatigue on EMG recovery curves both for painful and non-painful synergists probably by a central effect. These effects can modify the normal patterns of synergistic activation and can also generate overload problems in muscle pain patients if compensatory motor control strategies are applied.

Topics: Adult; Analysis of Variance; Ankle; Electromyography; Female; Humans; Isometric Contraction; Male; Muscle Fatigue; Muscle, Skeletal; Pain; Pain Measurement; Saline Solution, Hypertonic; Time Factors; Torque

In this study the stress protein response to unaccustomed maximal eccentric exercise in humans was investigated. Eleven healthy males performed 300 maximal eccentric actions with the quadriceps muscle. Biopsies from vastus lateralis were collected at 30 min and 4, 8, 24, 96, and 168 h after exercise. Cellular regulation and localization of heat shock protein (HSP) 27, alpha B-crystallin, and HSP70 were analyzed by immunohistochemistry, ELISA technique, and Western blotting. Additionally, mRNA levels of HSP27, alpha B-crystallin, and HSP70 were quantified by Northern blotting. After exercise (30 min), 81 +/- 8% of the myofibers showed strong HSP27 staining (P < 0.01) that gradually decreased during the following week. alpha B-Crystallin mimicked the changes observed in HSP27. After exercise (30 min), the ELISA analysis showed a 49 +/- 13% reduction of the HSP27 level in the cytosolic fraction (P < 0.01), whereas Western blotting revealed a 15-fold increase of the HSP27 level in the myofibrillar fraction (P < 0.01). The cytosolic HSP70 level increased to 203 +/- 37% of the control level 24 h after exercise (P < 0.05). After 4 days, myofibrillar-bound HSP70 had increased approximately 10-fold (P < 0.01) and was accompanied by strong staining on cross sections. mRNA levels of HSP27, alpha B-crystallin, and HSP70 were all elevated the first day after exercise (P < 0.01); HSP70 mRNA showed the largest increase (20-fold at 8 h). HSP27 and alpha B-crystallin seemed to respond immediately to maximal eccentric exercise by binding to cytoskeletal/myofibrillar proteins, probably to function as stabilizers of disrupted myofibrillar structures. Later, mRNA and total HSP protein levels, especially HSP70, increased, indicating that HSPs play a role in skeletal muscle recovery and remodeling/adaptation processes to high-force exercise.

Topics: Adaptation, Physiological; Adult; alpha-Crystallin B Chain; Creatine Kinase; Cytosol; Exercise; Heat-Shock Proteins; HSP27 Heat-Shock Proteins; HSP70 Heat-Shock Proteins; Humans; Immunohistochemistry; Male; Molecular Chaperones; Myofibrils; Neoplasm Proteins; Pain; Quadriceps Muscle; RNA, Messenger; Torque

Massive rotator cuff tears impose restraints on overhand arm functionality and are often accompanied by pain. After musculotendinous Teres Major transfer, overhand arm function is generally restored and pain is reduced. The assumed mechanical abduction insufficiency and Teres Major muscle function adaptation will be experimentally verified.. Principal Teres Major muscle activation (surface IEMG averaged over 3s) is recorded for 12-24 isometric and isotonic force directions perpendicular to the 60 degrees forward flexed humerus in three conditions: prior to surgery (n = 6 patients), prior to surgery and after subacromial anaesthetic (n = 6) and post-surgery (n = 3). Principal direction and on-, offset directions were estimated.. Teres Major activation adapts both to pathological and post surgery conditions: the normal activation during adduction changes into activation during forward flexion or abduction. Glenohumeral stabilisation, not abduction torque, seems to be the explanation for post surgery Teres Major transfer success.. The pathological absence of Supraspinatus and Infraspinatus forces during forward flexion result in increased upward glenohumeral instability. The superior translations are compensated for by Teres Major activity during forward flexion. This translation-'force' function conflicts with the adduction-generating rotation-'torque' function. This may explain the pain-induced reduction of arm elevation in these patients. Musculotendinous transfer solves the force-torque conflict by changing the moment arm of the Teres Major from adduction to abduction. Teres Major can now both compensate for the loss of Supraspinatus and Infraspinatus forces needed for glenohumeral stabilisation and contribute to forward flexion of the arm.

Topics: Biomechanical Phenomena; Electromyography; Female; Humans; Male; Middle Aged; Muscle, Skeletal; Pain; Range of Motion, Articular; Recovery of Function; Rotator Cuff; Rotator Cuff Injuries; Salvage Therapy; Tendon Injuries; Tendon Transfer; Tendons; Torque; Treatment Outcome

Healthy untrained men (age 20.4+/-1.7 years, n=20) volunteered to participate in an experiment in order to establish dynamics of indirect symptoms of skeletal muscle damage (ISMD) (decrease in maximal isometric voluntary contraction torque (MVCT) and torque evoked by electrostimulation at different frequencies and at different quadriceps muscle length, height (H) of drop jump (DJ), muscle soreness and creatine kinase (CK) activity in the blood) after 100 DJs from 0.75 m height performed with maximal intensity with an interval of 20s between the jumps (stretch-shortening exercise, SSE). All ISMDs remained even 72 h after SSE (P<0.01-0.001). The muscle experienced greater decrease (P<0.01) in torque evoked by electrostimulation (at low stimulation frequencies and at short muscle length in particular) after SSE than neuromuscular performance (MVCT and H of DJ) which demonstrated secondary decrease (P<0.01) in neuromuscular performance during the first 48 h after SSE. Within 24-72 h after the SSE the subjects felt an acute muscle pain (5-7 points approximately) and the CK activity in the blood was significantly increased up to 1200 IU/L (P<0.001). A significant correlation between decrease in MVCT and H of DJ 24-48 h after SSE on the one hand and muscle soreness registered within 24-48 h after SSE on the other was observed, whereas correlation between the other indirect symptoms of skeletal muscle damage was not significant.

Topics: Acute Disease; Adult; Analysis of Variance; Biomarkers; Creatine Kinase; Electric Stimulation; Heart Rate; Humans; Isometric Contraction; Male; Muscle Fatigue; Muscle Stretching Exercises; Muscular Diseases; Pain; Physical Endurance; Quadriceps Muscle; Reflex, Stretch; Torque

Muscle contractions present the main source of unpleasant sensations for patients undergoing electrochemotherapy. The contractions are a consequence of high voltage pulse delivery. Relatively low repetition frequency of these pulses (1 Hz) results in separate muscle contractions associated with each single pulse that is delivered. It would be possible to reduce the number of unpleasant sensations by increasing the frequency of electric pulses above the frequency of tetanic contraction, provided that the antitumor efficiency of electrochemotherapy remains the same. These assumptions were investigated in the present paper by measuring the muscle torque at different pulse repetition frequencies and at two different pulse amplitudes in rats and studying the antitumor efficiency of electrochemotherapy at different pulse repetition frequencies on tumors in mice. Measurements of muscle torque confirmed that pulse frequencies above the frequency of tetanic contraction (>100 Hz) reduce the number of individual contractions to a single muscle contraction. Regardless of the pulse amplitude, with increasing pulse frequency muscle torque increases up to the frequency of 100 or 200 Hz and then decreases to a value similar to that after application of a 1 Hz pulse train. Electrochemotherapy in vivo with higher repetition frequencies inhibits tumor growth and is efficient at all pulse frequencies examined (1 Hz-5 kHz). These results suggest that there is a considerable potential for clinical use of high frequency pulses in electrochemotherapy.

Topics: Animals; Antineoplastic Agents; Cell Proliferation; Drug Delivery Systems; Electricity; Electroporation; Muscle Contraction; Neoplasms; Pain; Rats; Torque

The aim of this human study was to investigate if voluntary EMG activity and supra-maximal M-wave are affected by injection of hypertonic saline to experimentally induce muscle pain.. Surface EMG signals were recorded with an electrode array from the tibialis anterior muscle of 12 subjects. Two sets of 6 contractions, 3 electrically elicited and 3 voluntary (30% of the maximal force), alternated, were performed with each leg. During the second set of 6 contractions, hypertonic (painful; right leg) or isotonic (non-painful; left leg) saline was injected 3 times (0.2, 0.5, 0.9 ml), separated by 140 s, into the tibialis anterior.. In the voluntary contractions, EMG average rectified value (ARV) significantly decreased (mean+/-SE, 13.2 +/- 4.2%) with increasing pain, although the exerted torque was unaltered. Conduction velocity (CV) (4.2 +/- 0.2 and 4.4 +/- 0.3 m/s, right and left leg, respectively) and mean power spectral frequency (MPF) (119.0 +/- 8.4 and 119.5+/-8.9 Hz) were not affected by the injection of hypertonic saline. In the electrically elicited contractions, M-wave CV (4.6 +/- 0.3 and 4.7 +/- 0.2 m/s), ARV (748.6 +/- 101.8 and 822.3 +/- 104.4 microV), and MPF (72.0+/-5.1 and 76.9+/-4.8 Hz) did not change with pain.. Injection of hypertonic saline did not change muscle fiber conduction velocity or impaire neuromuscular transmission. The decrease in voluntary EMG activity with injection of hypertonic saline was thus due to central factors.. The injection of hypertonic saline provides a model for exciting nociceptive afferents without affecting muscle fiber electrophysiological properties.

Topics: Action Potentials; Adult; Electromyography; Female; Humans; Male; Motor Neurons; Movement; Muscle Contraction; Muscle, Skeletal; Neural Conduction; Neural Inhibition; Neuromuscular Junction; Nociceptors; Pain; Reflex; Saline Solution, Hypertonic; Skin; Synaptic Transmission; Torque; Transcutaneous Electric Nerve Stimulation; Volition

Muscle damage reduces voluntary force after eccentric exercise but impaired neural drive to the muscle may also contribute. To determine whether the delayed-onset muscle soreness, which develops approximately 1 day after exercise, reduces voluntary activation and to identify the possible site for any reduction, voluntary activation of elbow flexor muscles was examined with both motor cortex and motor nerve stimulation. We measured maximal voluntary isometric torque (MVC), twitch torque, muscle soreness and voluntary activation in eight subjects before, immediately after, 2 h after, 1, 2, 4 and 8 days after eccentric exercise. Motor nerve stimulation and motor cortex stimulation were used to derive twitch torques and measures of voluntary activation. Eccentric exercise immediately reduced the MVC by 38 +/- 3% (mean +/- s.d., n = 8). The resting twitch produced by motor nerve stimulation fell by 82 +/- 6%, and the estimated resting twitch by cortical stimulation fell by 47 +/- 15%. While voluntary torque recovered after 8 days, both measures of the resting twitch remained depressed. Muscle tenderness occurred 1-2 days after exercise, and pain during contractions on days 1-4, but changes in voluntary activation did not follow this time course. Voluntary activation assessed with nerve stimulation fell 19 +/- 6% immediately after exercise but was not different from control values after 2 days. Voluntary activation assessed by motor cortex stimulation was unchanged by eccentric exercise. During MVCs, absolute increments in torque evoked by nerve and cortical stimulation behaved differently. Those to cortical stimulation decreased whereas those to nerve stimulation tended to increase. These findings suggest that reduced voluntary activation contributes to the early force loss after eccentric exercise, but that it is not due to muscle soreness. The impairment of voluntary activation to nerve stimulation but not motor cortical stimulation suggests that the activation deficit lies in the motor cortex or at a spinal level.

Topics: Adult; Brachial Plexus; Elbow Joint; Electric Stimulation; Electromyography; Female; Humans; Male; Middle Aged; Motor Cortex; Motor Neurons; Muscle Contraction; Muscle, Skeletal; Pain; Torque; Volition

This experiment investigated maximum forearm pronation and supination torques and forearm discomfort, for intermittent torque exertions in supine and prone forearm angles for the right arm. Twenty-two subjects participated in the study that comprised two parts, the first of which involved measurement of maximum forearm torque in both twisting directions at five forearm angles including neutral. This was followed by endurance tests at 50% maximum voluntary contraction (MVC) in both directions. The second part of the study involved subjects performing 5-min duration of intermittent isometric torque exercises at 20% MVC in both directions at 11 forearm angles. Regression equations were developed that accurately predict torques as a function of forearm angle expressed as a percentage of maximum motion. Analysis of the discomfort data for the intermittent isometric torque exertions indicated that both forearm angle and twisting direction significantly affected forearm discomfort (p < 0.001). A significant two-way interaction (p < 0.01) was identified between forearm angle and direction for supine forearm angles only. The results provide important strength and discomfort models for the design of tasks involving static or repetitive forearm twisting. Such tasks have a strong association with forearm injuries including lateral and medial epicondylitis. These results provide needed data on the risk factors associated with these injuries so they can be prevented.

Topics: Adult; Biomechanical Phenomena; Forearm; Hand Strength; Humans; Male; Pain; Physical Endurance; Pronation; Range of Motion, Articular; Supination; Torque

The repeated bout effect (RBE) is a phenomenon characterized by less delayed onset muscle soreness (DOMS) and torque deficit after the second of 2 separate eccentric exercise bouts. Previous investigators have reported that shifting of optimum angle after an initial bout of eccentric exercise mediates the RBE. We hypothesized that an RBE for elbow extensor exercise occurs after an initial bout performed at long (starting position of 50 degrees to an end position of 130 degrees) but not short (starting position of 0 degrees to an end position of 80 degrees) muscle length because strain at long length evokes a shifting of the optimum angle to a longer length. Untrained women performed an initial bout at either long or short length (n = 9 per group) followed 1 week later by a repeated bout (RB) through the full ROM (0-130 degrees). Extensor torque and optimum angle was evaluated before, immediately after, and 2 days after each bout. A mechanical transducer depressed on the triceps brachii quantified DOMS. Torque deficits were 3% and 7% after exercise at short vs. long length, respectively. Two days after the RB, torque deficit was 8% and 1% for those previously exercising at short vs. long length (group x bout, p < 0.05). Greater DOMS (N) was observed after exercise at long (16 +/- 3) vs. short (23 +/- 2) length; whereas greater DOMS occurred for the short-length (17 +/- 2) vs. long (26 +/- 3) group after the RB (group x bout, p < 0.05). Optimum angle shifted to a longer length after exercise at long (+10 +/- 4 degrees) vs. short (+1 +/- 3 degrees) length (group x bout, p < 0.05). After the RB, those exercising previously at short length experienced a shift of +15 +/- 4 degrees (main effect, p < 0.05). The findings of this study indicate that the repetitive strain at long but not short muscle length evokes both immediate and sustained shifts in optimum angle to longer lengths, and that this shifting mediates (r(2) = 0.71) the RBE.

Topics: Adult; Elbow Joint; Female; Humans; Muscle Contraction; Muscle, Skeletal; Pain; Physical Education and Training; Range of Motion, Articular; Rest; Torque; Transducers

Cross sectional.. To compare the strength and range of motion of the dominant and nondominant shoulders of adult female amateur tennis players. The secondary purpose of the study was to examine whether there were any differences in the observed relationships between women with a past history of shoulder pain and those with no history of shoulder pathology.. Information on characteristics of the shoulder in amateur female tennis players is scarce, as research has concentrated on highly skilled or male players, despite the cumulative prevalence of shoulder pain in this group.. Fifty-one female competitive, amateur tennis players (average age, 45 years) were tested bilaterally for shoulder internal/external rotation passive range of motion and isokinetic concentric strength.. Shoulder range of motion and strength ratios were comparable between sides. In the dominant arm, the total rotational range of motion was 221 degrees, with an internal to external rotator peak torque ratio of 1.05. External rotator strength was significantly greater in the dominant arm of individuals with no history of pain.. Range of motion and strength adaptations widely reported in highly skilled tennis players were not apparent in amateur female players. In assessment and management, clinicians should regard the amateur female tennis player as a separate entity from the highly skilled player.

Topics: Adult; Age Factors; Aged; Cross-Sectional Studies; Female; Functional Laterality; Humans; Middle Aged; Pain; Range of Motion, Articular; Shoulder Joint; Tennis; Torque

Superimposed electrical stimulation techniques can be used to detect central activation failure (CAF), that is, incomplete central nervous system recruitment or suboptimal activation of motor units. The purpose of this study was to evaluate the effects of two stimulation parameters on perceived discomfort and torque increment size and variability. Discomfort was evaluated using a visual analog scale (0-100 mm) for pain. The rectus femoris muscle of the dominant leg of 24 young healthy men was stimulated during submaximal (80% maximal) voluntary contractions. The size and variability of torque increments and perceived discomfort were assessed following stimulation with: (1) pulse trains (100 HZ, 150 V, 0.2-ms pulse duration) of different lengths (50 ms and 100 ms); and (2) pulse trains (100 HZ, 100 ms, 150 V) with different pulse durations (0.2 ms and 0.1 ms). Pulse trains of 100 ms generated larger torque increments and produced less variability, but caused more discomfort than pulse trains of 50 ms. Average discomfort ratings for pulse trains of 100 ms were 43.1 mm, and of 50 ms were 53.2 mm. There was no difference in torque increment size or in variability between pulse trains with pulse durations of 0.1 ms and 0.2 ms, whereas discomfort was less for the shorter pulse durations; average discomfort ratings were 53.1 mm and 58.1 mm for pulse durations of 0.1 ms and 0.2 ms, respectively. Thus, the appropriate selection of stimulation parameters can reduce discomfort but maintain the ability to detect CAF.

Topics: Adult; Electric Stimulation; Humans; Isometric Contraction; Knee Joint; Male; Motor Neurons; Muscle, Skeletal; Pain; Pain Measurement; Perception; Torque

A single bout of eccentric exercise induces a protective adaptation against damage from a repeated bout. The aim of this study was to determine whether this repeated bout effect is due to a change in the length-tension relationship. Twelve individuals performed an initial bout of six sets of 10 eccentric quadriceps contractions and then performed a repeated bout 2 weeks later. Eccentric contractions were performed on an isokinetic dynamometer at 1.04 rad x s(-1) with a target intensity of 90% of isometric strength at 70 degrees of knee flexion. Isometric strength and pain were recorded before and after both eccentric bouts and on each of the next 3 days. Isometric strength was tested at 30 degrees, 50 degrees, 70 degrees, 90 degrees and 110 degrees of knee flexion. On the days following the initial bout, there was a significant loss of isometric strength at all knee flexion angles except 110 degrees (bout x angle: P < 0.01). On day 2, strength averaged 86% of baseline for 30-90 degrees and 102% of baseline for 110 degrees. Strength loss and pain after the initial bout was contrasted by minimal changes after the repeated bout (pain: P < 0.001; strength: P < 0.01). The repeated bout effect was associated with a rightward shift in the length-tension curve; before the repeated bout, isometric strength was 6.8% lower at 30 degrees and 13.6% higher at 110 degrees compared with values before the initial bout (bout x angle: P < 0.05). Assuming that torque production at 110 degrees occurs on the descending limb of the length-tension curve, the increase in torque at 110 degrees may be explained by a longitudinal addition of sarcomeres. The addition of sarcomeres would limit sarcomere strain for subsequent eccentric contractions and may explain the repeated bout effect observed here.

Topics: Adult; Biomechanical Phenomena; Exercise; Female; Humans; Isometric Contraction; Knee Joint; Male; Muscle, Skeletal; Pain; Torque

Muscle weakness frequently accompanies conditions with musculoskeletal pain. It is not clear if this attenuation of force is due to peripheral or central processes. The effect of experimental muscle pain on maximal voluntary contraction torque and peripheral contractile properties was therefore assessed. Experimental muscle pain reduced the torque produced by isometric knee extension, but the contractile properties assessed by twitch interpolation were not affected. This indicates that force inhibition by muscle pain is centrally mediated. This has clinical implications for rehabilitation and training of patients with musculoskeletal pain.

Topics: Adult; Afferent Pathways; Female; Humans; Male; Middle Aged; Muscle Contraction; Muscle Weakness; Muscle, Skeletal; Musculoskeletal Diseases; Neural Inhibition; Neurons, Afferent; Nociceptors; Pain; Pain Measurement; Reaction Time; Reflex; Spinal Cord; Torque

The purpose of this study was to examine the time-course and relationships of technetium-99m (99mTc) neutrophils in muscle, interleukin-6 (IL-6), myosin heavy chain fragments (MHC), eccentric torque, and delayed onset muscle soreness (DOMS) following eccentric exercise in humans. Twelve male subjects completed a pre-test DOMS questionnaire, performed a strength test and had 100 ml blood withdrawn for analysis of plasma IL-6 and MHC content. The neutrophils were separated, labelled with 99mTc, and re-infused into the subjects immediately before the exercise. Following 300 eccentric repetitions of the right quadriceps muscles on an isokinetic dynamometer, the subjects had 10 ml of blood withdrawn with repeated the eccentric torque exercise tests and DOMS questionnaire at 0, 2, 4, 6, 20, 24, 48, 72 h, and 6 and 9 days. Bilateral images of the quadriceps muscles were taken at 2, 4, and 6 h. Computer analysis of regions of interest was used to determine the average count per pixel. The 99mTc neutrophils and IL-6 increased up to 6 h post-exercise (P < 0.05). The neutrophils were greater in the exercised muscle than the non-exercised muscle (P < 0.01). The DOMS was increased from 0 to 48 h, eccentric torque decreased from 2 to 24 h, and MHC peaked at 72 h post-exercise (P < 0.001). Significant relationships were found between IL-6 and 2 h and DOMS at 24 h post-exercise (r = 0.68) and assessment of the magnitude of change between IL-6 and MHC (r = 0.66). These findings suggest a relationship between damage to the contractile proteins and inflammation, and that DOMS is associated with inflammation but not with muscle damage.

Topics: Adult; Biomarkers; Humans; Interleukin-6; Male; Myofibrils; Myosin Heavy Chains; Myositis; Neutrophils; Pain; Physical Exertion; Technetium; Torque

We hypothesized that activation of the quadriceps femoris muscle group during eccentric exercise is related to the increase in magnitude of several markers of muscle injury that developed during the next week. Fourteen male subjects performed six to eight sets of five to ten repetitions of single-leg eccentric-only seated knee extension exercise. Magnetic resonance (MR) images were collected before and immediately after exercise and on days 2-4 and 6 after eccentric exercise. Changes in maximal voluntary contraction (MVC), perceived soreness, muscle volume and muscle transverse relaxation of water protons (T2) were determined for the quadriceps femoris muscle group each day. Changes in muscle volume and T2 were determined every day for each muscle [vastus lateralis (VL), vastus medialis (VM), vastus intermedius (VI), rectus femoris (RF)] of the quadriceps femoris group. Post-exercise T2 was greater than pre-exercise T2 (P < 0.05) for all muscles. The acute deltaT2 (Post-Pre) was similar (P>0.05) among VL, VM, VI, and RF [5.5 (0.3) ms], suggesting that the four muscles were equally activated during eccentric exercise. In the week after eccentric exercise, subjects experienced delayed-onset muscle soreness (DOMS) and all muscles demonstrated a delayed increase in T2 above pre-exercise values (P < 0.05), suggesting that muscle injury had occurred. For the quadriceps femoris muscle group, there was no correlation between acute deltaT2 and delayed (peak T2 during days 2, 3, 4, 6 minus pre-exercise T2) deltaT2 (r=0.04, P>0.05). Similar results were obtained when VL, VM, VI and RF were examined separately. Of the four muscles in quadriceps femoris, the biarticular RF experienced greater muscle injury [delayed deltaT2= 15.2 (2.0) ms] compared to the three monoarticular vasti muscles [delayed deltaT2 = 7.7 (1.3) ms; P< 0.05]. We propose that the disproportionate muscle injury to RF resulted from an ineffective transfer of torque from the knee to hip joint during seated eccentric knee extension exercise, thus causing RF to dissipate greater energy than normal. We conclude that in humans, muscle activation is not a unique determinant of muscle injury.

Topics: Adult; Exercise; Humans; Knee Joint; Magnetic Resonance Imaging; Male; Muscle Relaxation; Muscle, Skeletal; Pain; Torque

The purpose of this study was to evaluate the sex differences in delayed onset muscle soreness (DOMS), torque, and accumulation of technetium-99m (Tc-99m) neutrophils in eccentric-exercised muscle. A group of 10 female and 12 male subjects took part in this study. The subjects completed a pre-test using the descriptor differential scale (DDS) to describe DOMS, and tests of concentric and eccentric torque of the right quadriceps. A volume of 100 ml of blood was taken by venipuncture for neutrophil labelling in the early morning of the exercise day. The Tc-99m neutrophils were re-infused intravenously before the eccentric exercise. The exercise stimulus consisted of 300 eccentric repetitions of the right quadriceps muscles. Radionuclide images of both quadriceps muscles (lateral views) were taken at 2 and 4 h. The DDS, and concentric and eccentric torques of the quadriceps were subsequently evaluated at 0 h, 2, 4, 20 and 24 h post-exercise. The presence of Tc-99m neutrophils was greater in the exercised leg than the non-exercised leg at 2 and 4 h post-exercise (P

Topics: Adult; Exercise; Female; Humans; Leg; Male; Muscle, Skeletal; Neutrophils; Pain; Reaction Time; Sex Characteristics; Technetium; Torque

Nine patients treated surgically for Achilles tendon rupture (7 patients) or tendinosis (2 patients) with primary repair or debridement and augmentation with the flexor hallucis longus muscle-tendon unit were evaluated at a mean of 19 months postoperative. Subjective evaluation revealed a high level of satisfaction. All patients returned to work and only two patients reported limitation in their recreational activities. The mean post-operative AOFAS Ankle-Hindfoot Score was 90 points. Four patients reported mild occasional pain and one patient complained of moderate daily pain. Motion assessment showed a 20% increase in the hallux MTP dorsiflexion compared to the non-operative side (p = 0.045). No difference in ankle motion was noted. Cybex II+ dynamic evaluation of plantarflexion peak torque was complete on both extremities. The torque deficit on the reconstructed extremity was 20% (p = 0.01) at 120 degrees per second and 26% (p = 0.003) at 30 degrees per second. There is no significant difference between the torque deficit recorded for patients with Achilles rupture and those with Achilles tendinosis. A trend toward improved torque production with longer follow up was observed.

Topics: Achilles Tendon; Adult; Aged; Ankle Joint; Debridement; Employment; Female; Follow-Up Studies; Foot; Hallux; Heel; Humans; Male; Metatarsophalangeal Joint; Middle Aged; Muscle Contraction; Muscle, Skeletal; Muscular Diseases; Pain; Patient Satisfaction; Recreation; Rupture, Spontaneous; Tendons; Torque; Treatment Outcome

Anterior knee pain (AKP) is a common pathological condition, particularly among young people and athletes, associated to an abnormal motion of the patella during the bending of the knee and possibly dependent on a muscular or structural imbalance. A lack of synergy in the quadriceps muscles results in a dynamic misalignment of the patella, which in turn produces pain. AKP rehabilitative therapy consists of conservative treatment whose main objective is to strengthen the Vastus Medialis. The aim of this article is to study the quadriceps muscle control strategy in AKP patients during an isokinetic exercise. Analysis of the muscle activation strategy is important for an objective measurement of the knee functionality in that it helps to diagnose and monitor the rehabilitative treatment. Surface electromyography (EMG) from the three superficial muscles of the femoral quadriceps during a concentric isokinetic exercise has been analyzed along with the signals of knee joint position and torque. A group of 12 AKP patients has been compared with a group of 30 normal subjects. Analysis of the grand ensemble average of the EMG linear envelopes in AKP patients reveals significant modifications in Vastus Medialis activity compared to the other quadriceps muscles. In order to study the synergy of the muscles, temporal identifiers have been associated to the EMG linear envelopes. To this end, EMG linear envelope decomposition in Gaussian pulses turned out to be effective and the results highlight an appreciable delay in the activation of the Vastus Medialis in AKP patients. This muscular unbalance can explain the abnormal motion of the patella.

Topics: Adolescent; Adult; Biomechanical Phenomena; Case-Control Studies; Electromyography; Exercise Test; Humans; Isotonic Contraction; Knee Joint; Linear Models; Male; Muscle, Skeletal; Normal Distribution; Pain; Range of Motion, Articular; Signal Processing, Computer-Assisted; Torque

In this study we investigated the effect of human experimental muscle pain on H- and stretch reflexes as indicators of changes in muscle spindle sensitivity. Fourteen healthy, male volunteers participated in the study. Muscle pain was produced by infusion of 5% hypertonic saline over a period of 10-15 min in m. soleus and in m. tibialis anterior. Reflexes were elicited in the relaxed and active soleus muscle (10-15 Nm ankle torque) before, during and after muscle pain. Control measurements were made with infusions of 0.9% isotonic saline. Surface electromyograms (EMG) were measured from the soleus muscle, and torque was measured from the ankle joint. With pain in the soleus muscle the mechanical stretch reflex response (ankle torque) increased significantly (P = 0.0007) as compared to before pain. With pain in the tibialis anterior muscle both the mechanical and EMG responses increased significantly (P = 0.001; P = 0.0003) as compared to before pain. The H-reflex showed no significant changes during the infusions in either muscles. This study has demonstrated a muscle pain-related increase in the amplitude of the stretch reflex without a corresponding increase in the H-reflex amplitude. One explanation could be an increased dynamic sensitivity of the muscle spindles during muscle pain caused by an increased firing rate in the dynamic gamma-motoneurones. However, the data could not support the vicious cycle model because the excitability of the alpha-motoneurone pool was unchanged.

Topics: Adult; Electromyography; H-Reflex; Humans; Injections, Intramuscular; Isotonic Solutions; Male; Muscles; Pain; Reflex, Stretch; Saline Solution, Hypertonic; Sodium Chloride; Torque

Variations in the levels of muscle hemoglobin and of myoglobin oxygen saturation can be detected non-invasively with near-infrared spectroscopy. This technique could be applied to the diagnosis of chronic compartment syndrome, in which invasive testing has shown increased intramuscular pressure associated with ischemia and pain during exercise. We simulated chronic compartment syndrome in ten healthy subjects (seven men and three women) by applying external compression, through a wide inflatable cuff, to increase the intramuscular pressure in the anterior compartment of the leg. The tissue oxygenation of the tibialis anterior muscle was measured with near-infrared spectroscopy during gradual inflation of the cuff to a pressure of forty millimeters of mercury (5.33 kilopascals) during fourteen minutes of cyclic isokinetic dorsiflexion and plantar flexion of the ankle. The subjects exercised with and without external compression. The data on tissue oxygenation for each subject then were normalized to a scale of 100 per cent (the baseline value, or the value at rest) to 0 per cent (the physiological minimum, or the level of oxygenation achieved by exercise to exhaustion during arterial occlusion of the lower extremity). With external compression, tissue oxygenation declined at a rate of 1.4 +/- 0.3 per cent per minute (mean and standard error) during exercise. After an initial decrease at the onset, tissue oxygenation did not decline during exercise without compression. The recovery of tissue oxygenation after exercise was twice as slow with compression (2.5 +/- 0.6 minutes) than it was without the use of compression (1.3 +/- 0.2 minutes).

Topics: Adolescent; Adult; Chronic Disease; Compartment Syndromes; Female; Hemoglobins; Humans; Ischemia; Isometric Contraction; Leg; Male; Middle Aged; Monitoring, Physiologic; Muscle Contraction; Muscle, Skeletal; Myoglobin; Oxygen Consumption; Pain; Physical Endurance; Physical Exertion; Pressure; Spectroscopy, Near-Infrared; Torque

The purpose of this investigation was to determine the influence of pain and muscle weakness on gait variables in subjects with patellofemoral pain (PFP).. Nineteen female subjects with a diagnosis of PFP and 19 female subjects without PFP participated in the study.. Subjects underwent gait analysis (stride characteristics and joint motion) during level walking, ascending and descending stairs, and ascending and descending ramps, in addition to isometric torque testing of the knee extensors of the involved limb. Pain and functional status also were assessed.. Compared with the comparison group, the primary gait compensation in the PFP group was a reduced walking speed, which was a function of both a reduced stride length and cadence. Knee extensor torque was the only predictor of gait function, with increased torque correlating with improved stride characteristics. In addition, PFP was not associated with locomotor function.. These findings suggest that functional ability in persons with PFP is associated with increased quadriceps femoris muscle torque. Future research is needed to determine whether function improves with quadriceps femoris muscle strengthening.

Topics: Adolescent; Adult; Female; Gait; Humans; Knee Joint; Middle Aged; Muscle Weakness; Muscle, Skeletal; Pain; Thigh; Torque

The purpose of this study was to determine whether a post-exercise cryotherapy protocol could facilitate recovery of elbow flexor strength and reduce the severity of delayed onset muscle soreness following eccentric exercise. Eight resistance-trained males (23 +/- 3 yr) performed 64 eccentric elbow flexions with each arm. One arm was subjected to five, 20 minute immersions in a 5 +/- 1 degree C ice-water bath interspersed by 60 minute rest periods. The non-immersed arm served as the control. A main effect for time was observed for all dependent variables (p < 0.05). Isometric torque (mean SE) decreased from a pre-exercise value of 87.9 +/- 4.5 Nm to 65.2 +/- 4.5 Nm immediately post-exercise. Isokinetic torque at 60 and 300 degrees x s(-1) decreased from 71.0 +/- 3.5 NM and 48.4 +/- 2.8 Nm to 55.8 +/- 3.3 Nm and 39.8 +/- 3.1 Nm, respectively. All torque measures returned to pre-test levels by 72 h. Muscle soreness peaked 48 h post-exercise and was evident until 120 h. Limb volume increased by 200 +/- 18 ml immediately post-exercise (p < 0.05) but was not significantly elevated thereafter. No significant difference between the immersed and control arms were observed for any variable. The result suggest that the use of cryotherapy immediately following damaging eccentric exercise may not provide the same therapeutic benefits commonly attributed to cryotherapy following traumatic muscle injury.

Topics: Adult; Analysis of Variance; Arm; Cryotherapy; Exercise; Exercise Test; Humans; Ice; Inflammation; Male; Muscle, Skeletal; Pain; Torque

The aim of this study was to evaluate and compare muscular activation in sitting and standing in patients with patellofemoral pain syndrome and healthy controls. Eleven women with patellofemoral pain syndrome and nine healthy controls were evaluated regarding: (a) muscle performance in sitting compared to standing-knee extensor torque was registered in sitting with a Kin Com dynamometer and in standing with a force plate, and quadriceps muscle activity was registered with EMG in both sitting and standing; and (b) ability to maximally voluntarily activate during sitting isometric knee extension. Maximally tolerated single-twitch electrical stimulation was superimposed on 20, 40, 60, 80 and 100% of maximal voluntary activation. Additional torque from the single twitch was documented. Five patients and all nine controls were tested twice (tests a and b) with 2 days between tests, and high reproducibility could be demonstrated. A significantly higher torque during sitting compared with standing was found in both patients and controls, but with a significant correlation between sitting and standing torque values. No significant difference was found between patients and controls. Single-twitch electrical stimulation superimposed on maximal voluntary activation resulted in increased torque in two of the nine controls compared to 10 of the 11 patients. The average increased torque in the patients were significantly higher than in the controls and estimated to 18%. It was concluded that sitting isometric measurements are representative of the ability to produce standing isometric knee torque. A moderate degree of inhibition was demonstrated during sitting strength measurements in the patients (not studied in standing).

Topics: Adolescent; Adult; Electric Stimulation; Electromyography; Female; Femur; Humans; Isometric Contraction; Joint Diseases; Knee Joint; Muscle Contraction; Muscle, Skeletal; Pain; Patella; Posture; Reproducibility of Results; Syndrome; Torque; Weight-Bearing