vendex and Muscular-Diseases

Unaccustomed exercise causes muscle damage resulting in loss of muscle function, which may be attributable to exercise-induced increases in skeletal muscle reactive oxygen species. This study examined the effect of mitochondria-targeted antioxidant supplementation on recovery of muscle function following exercise. Thirty-two untrained men received MitoQ (20 mg/day) or a placebo for 14 days before performing  300 maximal eccentric contractions of the knee extensor muscles of 1 leg. Muscle function was assessed using isokinetic dynamometry before, immediately after, and 24, 48, 72, and 168 hours after exercise. Muscle soreness was assessed using a visual analogue scale 24, 48, 72, and 168 hours after exercise. Blood samples were collected before, immediately after, and 2, 24, 48, 72, and 168 hours after exercise and urine samples were collected before and during the 48 hours after exercise. The reduction in maximal voluntary isometric contraction force and peak concentric torque following exercise was unaffected by MitoQ while recovery of peak eccentric torque was delayed in the MitoQ group. Exercise-induced increases in urine F

Topics: Antioxidants; Creatine Kinase; Dietary Supplements; F2-Isoprostanes; Humans; Isometric Contraction; Male; Mitochondria; Muscle Contraction; Muscle, Skeletal; Muscular Diseases; Myalgia; Torque

The purpose of this study was to investigate the effects of a single-dose of β-hydroxy-β-methylbutyrate free acid (HMB-FA) supplementation on muscle recovery after a high-intensity exercise bout. Twenty-three trained young males were randomly assigned to receive either a single-dose supplementation of 3 g of HMB-FA (n = 12; age, 22.8 ± 3.0 years) or placebo (PLA; n = 11; age, 22.9 ± 3.1 years). A muscle damage protocol was applied 60 min after supplementation, and consisted of 7 sets of 20 drop jumps from a 60-cm box with 2-min rest intervals between sets. Muscle swelling, countermovement jump (CMJ), maximal voluntary isometric torque (MVIT), and work capacity (WC) were measured before, immediately after, and 24, 48, and 72 h after the exercise protocol. Muscle swelling, CMJ, and MVIT changed similarly in both groups after the exercise protocol (p < 0.001), but returned to pre-exercise levels after 24 h in both groups. WC decreased similarly in both groups after the exercise protocol (p < 0.01). For HMB-FA, WC returned to pre-exercise level 24 h after exercise protocol. However, for PLA, WC did not return to pre-exercise level even 72 h after the exercise protocol. In summary, a single-dose of HMB-FA supplementation improved WC recovery after a high-intensity exercise bout. However, HMB-FA did not affect the time-course of muscle swelling, MVIT, and CMJ recovery.

Topics: Adolescent; Adult; Dietary Supplements; Dose-Response Relationship, Drug; Double-Blind Method; Exercise; Humans; Male; Mental Recall; Muscle, Skeletal; Muscular Diseases; Resistance Training; Torque; Valerates; Young Adult

Quadriceps function improves after application of focal joint cooling or transcutaneous electrical nerve stimulation to the knee in patients with arthrogenic muscle inhibition (AMI), yet it is not known whether superficial heat is able to produce a similar effect.. To determine quadriceps function after superficial heat to the knee joint in individuals with AMI.. Single blinded randomized crossover.. Laboratory.. 12 subjects (4 female, 8 males; 25.6 ± 7.7 y, 177.2 ± 12.7 cm, 78.4 ± 18.2 kg) with a history of knee-joint pathology and AMI, determined with a quadriceps central activation ratio (CAR) of <90%.. 3 treatment conditions for 15 min on separate days: superficial heat using a cervical moist-heat pack (77 °C), sham using a cervical moist pack (room temperature at about 24 °C), and control (no treatment). All subjects received all treatment conditions in a randomized order.. Central activation ratio and knee-extension torque during maximal voluntary isometric contraction with the knee flexed to 60° were collected at pre, immediately post, 30 min post, and 45 min posttreatment. Skin temperature of the quadriceps and knee and room temperature were also recorded at the same time points.. Three (treatment conditions) by 4 (time) repeated ANOVAs found that there were no significant interactions or main effects in either CAR or knee-extension torque (all P > .05). Skin-temperature 1-way ANOVAs revealed that the skin temperature in the knee during superficial heat was significantly higher than other treatment conditions at all time points (P < .05).. Superficial heat to the knee joint using a cervical moist-heat pack did not influence quadriceps function in individuals with AMI in the quadriceps.

Topics: Adolescent; Adult; Cross-Over Studies; Female; Humans; Hyperthermia, Induced; Knee Joint; Male; Muscle Contraction; Muscular Diseases; Quadriceps Muscle; Single-Blind Method; Skin Temperature; Torque; Transcutaneous Electric Nerve Stimulation; 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

Exercise-induced muscle damage (EIMD) leads to decrements in muscle performance, increases in intramuscular proteins and delayed-onset of muscle soreness (DOMS). Previous research demonstrated that one litre of milk-based protein-carbohydrate (CHO) consumed immediately following muscle damaging exercise can limit changes in markers of EIMD possibly due to attenuating protein degradation and/or increasing protein synthesis. If the attenuation of EIMD is derived from changes in protein metabolism then it can be hypothesised that consuming a smaller volume of CHO and protein will elicit similar effects. Three independent matched groups of 8 males consumed 500 mL of milk, 1,000 mL of milk or a placebo immediately following muscle damaging exercise. Passive and active DOMS, isokinetic muscle performance, creatine kinase (CK), myoglobin and interleukin-6 were assessed immediately before and 24, 48 and 72 h after EIMD. After 72 h 1,000 mL of milk had a likely benefit for limiting decrements in peak torque compared to the placebo. After 48 h, 1,000 mL of milk had a very likely benefit of limiting increases in CK in comparison to the placebo. There were no differences between consuming 500 or 1,000 mL of milk for changes in peak torque and CK. In conclusion, decrements in isokinetic muscle performance and increases in CK can be limited with the consumption of 500 mL of milk.

Topics: Adolescent; Adult; Animals; Creatine Kinase; Dietary Supplements; Drinking Behavior; Eating; Exercise; Humans; Male; Milk; Muscular Diseases; Myoglobin; Placebos; Torque; Young Adult

This study tested the hypothesis that changes in indirect markers of muscle damage following maximal eccentric exercise would be smaller for the knee extensors (KE) and flexors (KF) compared with the elbow flexors (EF) and extensors (EE). A total of 17 sedentary men performed five sets of six maximal isokinetic (90° s(-1)) eccentric contractions of EF (range of motion, ROM: 90°-0°, 0 = full extension), EE (55°-145°), KF (90°-0°), and KE (30°-120°) using a different limb with a 4-5-week interval in a counterbalanced order. Changes in maximal isometric and concentric isokinetic strength, optimum angle, limb circumference, ROM, plasma creatine kinase activity and myoglobin concentration, muscle soreness, and echo-intensity of B-mode ultrasound images before and for 5 days following exercise were compared amongst the four exercises using two-way repeated-measures ANOVA. All variables changed significantly following EF, EE, and KF exercises, but KE exercise did not change the optimum angle, limb circumference, and echo-intensity. Compared with KF and KE, EF and EE showed significantly greater changes in all variables, without significant differences between EF and EE. Changes in all variables were significantly greater for KF than KE. For the same subjects, the magnitude of change in the dependent variables following exercise varied among the exercises. These results suggest that the two arm muscles are equally more susceptible to muscle damage than leg muscles, but KF is more susceptible to muscle damage than KE. The difference in the susceptibility to muscle damage seems to be associated with the use of muscles in daily activities.

Topics: Adult; Algorithms; Creatine Kinase; Exercise; Extremities; Humans; Male; Muscle Fatigue; Muscle Strength; Muscle, Skeletal; Muscular Diseases; Myoglobin; Organ Size; Range of Motion, Articular; Torque; Ultrasonography; Young Adult

The aim of this study was to examine changes in indirect markers of muscle damage during 3 weeks of stretch-shortening exercise with a progressively increasing load and continued modulation of various key training variables. Eight healthy untrained men performed a drop-jump programme involving a progressive increase in load impact with respect to the number of jumps performed, drop (platform) height, squat depth amplitude, and addition of weights. Maximal concentric and isometric knee extensor strength were assessed immediately before and 10 min after each training session. Voluntary and 100 Hz-stimulation-evoked torque decreased acutely after each training session relative to pre-exercise values (P < 0.05) but recovered before the subsequent training session. Post-exercise plasma creatine kinase activity increased from 162.2 ± 56.2 IU · l(-1) to 284.3 ± 116.3 IU · l(-1) at 48 h after the first training session (P < 0.05) and remained marginally elevated throughout the training period. The present results indicate that detrimental muscle damage can be avoided with drop-jump training even with the gradual introduction of more demanding exercise induced by increasing the volume, intensity, and muscle stretch amplitude. These findings suggest that the human neuromuscular system is highly adaptable to progressively varied loading demands during stretch-shortening exercise training.

Topics: Adult; Biomarkers; Creatine Kinase; Exercise; Humans; Knee; Knee Joint; Male; Movement; Muscle Contraction; Muscle Strength; Muscle, Skeletal; Muscular Diseases; Torque; Young Adult

Recent efforts to establish a role for plasma matrix metalloproteinase-9 (MMP-9) as a marker of exercise-induced muscle damage have been inconsistent. Methodological and experimental design issues have contributed to confusion in this area. The purpose of this study was to use a damaging eccentric arm task to evaluate the relationship between activity-induced muscle damage and plasma MMP-9 levels in humans while controlling for physical activity history and quantifying day-to-day variability of the dependent variables. Fourteen physically inactive males performed 6 sets of 10 eccentric contractions of the elbow flexors at 120% of their voluntary concentric maximum. Soreness ratings, maximum voluntary isometric strength, range of motion (ROM), limb circumference, and plasma creatine kinase (CK) and MMP-9 levels were measured at 2 time points before, immediately after, and 1, 2, 4, and 7 days post-exercise. Changes in traditional markers of muscle damage mirrored patterns previously reported in the literature, but plasma MMP-9 concentration and activity measured by ELISA and gelatin zymography were unchanged at all time points examined. Plasma levels of the MMP-9 inhibitor, tissue inhibitor of metalloproteinase-1 (TIMP-1), were also unchanged post-exercise. Finally, although mean MMP-9 levels were not significantly different between the two pre-exercise timepoints, the high total error of measurement and low day-to-day correlation suggest substantial within and between subject variability. Plasma MMP-9 levels are not a robust or reliable marker for eccentric exercise-induced damage of the elbow flexor musculature, though this may not preclude a role for MMPs in skeletal muscle remodeling in response to injury.

Topics: Adolescent; Adult; Biomarkers; Elbow; Elbow Joint; Exercise; Humans; Isometric Contraction; Male; Matrix Metalloproteinase 9; Muscle Contraction; Muscle Fatigue; Muscular Diseases; Range of Motion, Articular; Torque; 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

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

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

To examine differences in the electromyographic vs torque (EMG-T) relationship, as well as muscle strength and indicators of muscle mass and quality between young versus postmenopausal females, and explore whether the potential differences in the EMG-T relationships could be explained by differences in muscle mass.. Thirty young (age = 20.7 ± 2.8 y) and 30 postmenopausal (age = 56.3 ± 4.7 y) females completed maximal isometric strength testing (MVIT) and isometric ramp contractions at 40% and 70% MVIT, during which electromyographic signals were collected to quantify the slopes (Slope. Postmenopausal females exhibited lower skeletal muscle mass (- 2.3 ± 1.5 kg), fat-free mass index (- 1.1 ± 0.7 kg·m. Muscle mass and quality are primary contributors to the decrements in neuromuscular function observed in postmenopausal versus young females, and the preservation of muscle mass should be prioritized in the years leading up to, during, and immediately after menopause.

Topics: Adult; Body Weight; Body Weights and Measures; Electromyography; Female; Humans; Isometric Contraction; Middle Aged; Muscle Strength; Muscle, Skeletal; Muscular Diseases; Postmenopause; Torque; Young Adult

What is the central question of this study? Oestradiol (E. Oestradiol's effects on skeletal muscle are multifactorial including the preservation of mass, contractility and regeneration. Here, we aimed to determine the extent to which oestradiol deficiency affects strength recovery when muscle is challenged by multiple BaCl

Topics: Animals; Estradiol; Female; Longitudinal Studies; Mice; Mice, Inbred C57BL; Muscle Strength; Muscle, Skeletal; Muscular Diseases; Ovariectomy; Reinjuries; Satellite Cells, Skeletal Muscle; Torque

Hamstring injuries remain the most common injury type across many professional sports. Despite a variety of intervention strategies, its incidence in soccer players playing in the UEFA Champions League has increased by 4% per year over the last decade. Test batteries trying to identify potential risk factors have produced inconclusive results. The purpose of the current study was to prospectively record hamstring injuries, to investigate the incidence and characteristics of the injuries, and to identify possible risk factors in elite male soccer players, playing in the Kosovo national premier league. A total of 143 soccer players from 11 teams in Kosovo were recruited. To identify possible prevalent musculoskeletal or medical conditions a widespread health and fitness assessment was performed including isokinetic strength testing, Nordic hamstring strength test, functional tests, and a comprehensive anamnesis surveying previous hamstring injuries. On average 27.9% of the players sustained at least one hamstring injury with three players suffering bilateral strains with the re-injury rate being 23%. Injured players were significantly older and heavier and had a higher body mass index compared to non-injured ones (p < 0.05). There was a lower passing rate in the Nordic hamstring strength test and a higher injury incidence among the previously injured players compared to non-injured ones (p < 0.05). Except for hamstring/quadriceps ratio and relative torque at 60°/sec (p < 0.05) for dominant and non-dominant leg, there were no other significant differences in isokinetic strength regardless of the angular velocity. No differences were observed for functional tests between cohorts. Regression analysis revealed that age, Nordic hamstring strength test, previous injury history, and isokinetic concentric torque at 240°/sec could determine hamstring injuries by 25.9%, with no other significant predicting risk factors. The battery of laboratory and field-based tests performed during preseason to determine performance related skills showed limited diagnostic conclusiveness, making it difficult to detect players at risk for future hamstring injuries.

Topics: Adult; Athletic Injuries; Body Mass Index; Exercise; Hamstring Muscles; Humans; Kosovo; Male; Muscle Strength; Muscular Diseases; Prognosis; Prospective Studies; Risk Factors; Soccer; Torque; Young Adult

Electrophysiological measurements are used in longitudinal clinical studies to provide insight into the progression of amyotrophic lateral sclerosis (ALS) and the relationship between muscle weakness and motor unit (MU) degeneration. Here, we used a similar longitudinal approach in the Cu/Zn superoxide dismutase (SOD1[G93A]) mouse model of ALS.. In vivo muscle contractility and MU connectivity assays were assessed longitudinally in SOD1(G93A) and wild type mice from postnatal days 35 to 119.. In SOD1(G93A) males, muscle contractility was reduced by day 35 and preceded MU loss. Muscle contractility and motor unit reduction were delayed in SOD1(G93A) females compared with males, but, just as with males, muscle contractility reduction preceded MU loss.. The longitudinal contractility and connectivity paradigm employed here provides additional insight into the SOD1(G93A) mouse model and suggests that loss of muscle contractility is an early finding that may precede loss of MUs and motor neuron death. Muscle Nerve 59:254-262, 2019.

Topics: Action Potentials; Age Factors; Amyotrophic Lateral Sclerosis; Animals; Disease Models, Animal; Disease Progression; Female; Longitudinal Studies; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Motor Neurons; Muscle Contraction; Muscle, Skeletal; Muscular Diseases; Neuromuscular Junction; Superoxide Dismutase; Torque

Heightened local inflammation due to muscle trauma or disease is associated with impaired bone regeneration.. We hypothesized that FK506, an FDA approved immunomodulatory compound with neurotrophic and osteogenic effects, will rescue the early phase of fracture healing which is impaired by concomitant muscle trauma in male (~4 months old) Lewis rats. FK506 (1 mg/kg; i.p.) or saline was administered systemically for 14 days after an endogenously healing tibia osteotomy was created and fixed with an intermedullary pin, and the overlying tibialis anterior (TA) muscle was either left uninjured or incurred volumetric muscle loss injury (6 mm full thickness biopsy from middle third of the muscle).. The salient observations of this study were that 1) concomitant TA muscle trauma impaired recovery of tibia mechanical properties 28 days post-injury, 2) FK506 administration rescued the recovery of tibia mechanical properties in the presence of concomitant TA muscle trauma but did not augment mechanical recovery of an isolated osteotomy (no muscle trauma), 3) T lymphocytes and macrophage presence within the traumatized musculature were heightened by trauma and attenuated by FK506 3 days post-injury, and 4) T lymphocyte but not macrophage presence within the fracture callus were attenuated by FK506 at 14 days post-injury. FK506 did not improve TA muscle isometric torque production CONCLUSION: Collectively, these findings support the administration of FK506 to ameliorate healing of fractures with severe muscle trauma comorbidity. The results suggest one potential mechanism of action is a reduction in local T lymphocytes within the injured musculoskeletal tissue, though other mechanisms to include direct osteogenic effects of FK506 require further investigation.

Topics: Adaptive Immunity; Animals; Biopsy; Bone Nails; Bone Regeneration; Bony Callus; Disease Models, Animal; Fracture Fixation, Intramedullary; Fracture Healing; Humans; Immunity, Innate; Immunosuppressive Agents; Macrophages; Male; Muscle, Skeletal; Muscular Diseases; Osteotomy; Rats; Rats, Inbred Lew; Soft Tissue Injuries; T-Lymphocytes; Tacrolimus; Tibial Fractures; Torque

In myopathy patients, it is useful to measure skeletal muscle forces. Conventional methods require voluntary muscle activation, which can be unreliable. We evaluated a device for nonvoluntary force assessment.. We tested 8 patients (unknown myopathy n = 2, inflammatory myopathy, facioscapulohumeral muscular dystrophy, mitochondrial myopathy, dysferlinopathy, multi-minicore disease, Becker-Kiener muscular dystrophy, n = 1 each). Isometric twitch torques of ankle dorsiflexors were measured after fibular nerve stimulation.. Six patients had decreased torques vs. 8 controls (men: median Newton-meter 1.6 vs. 5.7, women: 0.2 vs. 3.9, both P < 0.0001). Values correlated with Manual Muscle Test results (r = 0.73; r(2) = 0.53; P < 0.0001). In weak dorsiflexors, torque could be measured despite lower signal-to-noise ratios. In 2 patients with hypertrophy, we measured increased torques.. Nonvoluntary muscle force assessment can be used in patients with myopathies, and values correlate with voluntary forces determined by traditional methods. Muscle Nerve 53: 913-917, 2016.

Topics: Adult; Ankle Joint; Electric Stimulation; Electromyography; Female; Humans; Isometric Contraction; Male; Middle Aged; Muscle, Skeletal; Muscular Diseases; Statistics as Topic; Statistics, Nonparametric; Switzerland; Torque

This study examined whether avoiding or experiencing exercise-induced muscle damage (EIMD) influences strength gain after downhill walking training. Healthy young males performed treadmill downhill walking (gradient: -28%, velocity: 5 km · h(-1) and load: 10% of body mass) 1 session per week for four weeks using either a ramp-up protocol (n = 16), where exercise duration was gradually increased from 10 to 30, 50 and 70 min over four sessions, or a constant protocol (n = 14), where exercise duration was 40 min for all four sessions. Indirect markers of EIMD were measured throughout the training period. Maximal knee extension torque in eccentric (-1.05 rad·s(-1)), isometric and concentric (1.05 rad·s(-1)) conditions were measured at pre- and post-training. The ramp-up group showed no indications of EIMD throughout the training period (e.g., plasma creatine kinase (CK) activity: always <185 U · L(-1)) while EIMD was evident after the first session in the constant group (CK: peak 485 U · L(-1)). Both groups significantly increased maximal knee extension torque in all conditions with greater gains in eccentric (ramp-up: +19%, constant: +21%) than isometric (+16%, +15%) and concentric (+12%, +10%) strength without any significant group-difference. The current results suggest that EIMD can be avoided by the ramp-up protocol and is not a major determinant of training-induced strength gain.

Topics: Adult; Creatine Kinase; Humans; Knee; Knee Joint; Male; Muscle Contraction; Muscle Strength; Muscular Diseases; Quadriceps Muscle; Torque; Walking; Young Adult

Eccentric contractions may cause immediate and long-term reductions in muscle strength that can be recovered through increased protein synthesis rates. The purpose of this study was to determine whether the mechanistic target-of-rapamycin complex 1 (mTORC1), a vital controller of protein synthesis rates, is required for return of muscle strength after injury.. Isometric muscle strength was assessed before, immediately after, and then 3, 7, and 14 days after a single bout of 150 eccentric contractions in mice that received daily injections of saline or rapamycin.. The bout of eccentric contractions increased the phosphorylation of mTORC1 (1.8-fold) and p70s6k1 (13.8-fold), mTORC1's downstream effector, 3 days post-injury. Rapamycin blocked mTORC1 and p70s6k1 phosphorylation and attenuated recovery of muscle strength (∼20%) at 7 and 14 days.. mTORC1 signaling is instrumental in the return of muscle strength after a single bout of eccentric contractions in mice. Muscle Nerve 54: 914-924, 2016.

Topics: Animals; Disease Models, Animal; Electric Stimulation; Female; Immunosuppressive Agents; Mice; Mice, Inbred C57BL; Muscle Contraction; Muscle, Skeletal; Muscular Diseases; Recovery of Function; Ribosomal Protein S6 Kinases, 70-kDa; Signal Transduction; Sirolimus; Time Factors; TOR Serine-Threonine Kinases; Torque

In this investigation we aimed to determine whether: (1) physical activity protects rat skeletal muscle from ischemia/reperfusion (I/R) injury; and (2) continued activity after I/R improves the rate of healing.. Rats were divided into sedentary or active (voluntary wheel running) groups. Active rats ran for 4 weeks before I/R or 4 weeks before plus 4 weeks after I/R.. Activity before I/R resulted in 73.2% less muscle damage (Evans blue dye inclusion). Sedentary and active rats had a similar decline in neural-evoked (∼ 99%) and directly stimulated (∼ 70%) in vivo muscle torque, and a similar reduction in junctophilin 1. Active rats produced 19% and 15% greater neural-evoked torque compared with sedentary rats at 14 and 28 days postinjury, respectively, although the rate of recovery appeared similar.. Activity protects against long-term muscle damage, but not short-term neural injury or excitation-contraction uncoupling. Continued activity neither accelerates nor hinders the rate of functional recovery.

Topics: Animals; Body Weight; Disease Models, Animal; Ischemia; Isometric Contraction; Male; Muscle Fibers, Skeletal; Muscular Diseases; Physical Conditioning, Animal; Rats; Rats, Inbred Lew; Regeneration; Reperfusion Injury; Running; Statistics, Nonparametric; Torque

What is the central question of this study? Do obesity-specific factors affect skeletal muscle performance in older individuals? What is the main finding and its importance? Older obese women have a larger quadriceps femoris size but develop lower tension per unit of skeletal muscle than their normal-weight counterparts. Muscle impairment and excess body mass are very common among older people. Given that the effect of obesity on strength production has scarcely been studied in older individuals, we analysed functional and structural characteristics of quadriceps femoris (QF) in obese (OB) and normal-weight (NW) older women with comparable habitual physical activity. In five OB (body mass index 36.8 ± 1.9 kg m(-2), age 72.4 ± 2.3 years) and six NW well-functioning older women (body mass index 24.3 ± 1.8 kg m(-2), age 72.7 ± 1.9 years), peak knee-extension torque (KET) was measured in isometric (90 deg knee flexion) and isokinetic conditions (240, 180, 120 and 60 deg s(-1)). Mid-thigh QF cross-sectional area (CSA) and muscle tissue fat content (MF%) were determined with magnetic resonance imaging (Dixon sequence). Muscle fascicle length and pennation angle (PA) were assessed with ultrasonography for each muscle belly of the QF (vastus lateralis, vastus intermedius, rectus femoris and vastus intermedius). Despite similar values of KET, CSA was 17.0% larger in OB than in NW women (P < 0.05), so that KET/CSA was significantly lower (P < 0.05) in OB women. Compared with NW women, OB women had 28.7% higher MF% (P < 0.05) and 24.9% higher average PA (P < 0.05), while fascicle length was similar. Overall, isometric KET/CSA was negatively affected by both MF% (P < 0.05) and PA (P < 0.05), while isokinetic KET/CSA was negatively affected only by MF% (P < 0.01). Muscle composition and architecture seem to be important determinants of KET/CSA in elderly women. In fact, owing to the effect of obesity overload, OB women have a larger QF size than NW women, but unfavourable muscle composition and architecture. The higher MF% and steeper PA observed in OB women are associated with reduced levels of muscle specific strength.

Topics: Adiposity; Age Factors; Aged; Biomechanical Phenomena; Body Mass Index; Case-Control Studies; Female; Humans; Isometric Contraction; Magnetic Resonance Imaging; Muscle Strength; Muscular Diseases; Obesity; Quadriceps Muscle; Sex Factors; Torque; Ultrasonography

The mechanical and metabolic characteristics of skeletal muscle fibers can interfere with muscle contractile performance in healthy subjects. Few studies have investigated the degree of association between muscle function and muscle fiber morphology in patients with myopathy. A biopsy was obtained from the left biceps brachii muscle of 12 subjects with myopathic disorders. The relative cross-sectional area of type 2 fibers and their subtypes was determined by the ATPase technique. Relative torque (RT) was calculated by dividing isokinetic elbow flexion peak torque (PT) values (90 and 180° s-1) by isometric PT values. Correlations were analyzed using Spearman's coefficient (r). The relative cross-sectional area of type 2b fibers was positively correlated with RT90 (r = 0.71, P = 0.009) and RT180 (r = 0.73, P = 0.007). The relative cross-sectional area of type 2a fibers showed a moderate and negative correlation with RT180 (r = -0.62, P = 0.03) and a low correlation with RT90 (r = -0.57, P = 0.05). In contrast to healthy subjects, patients with myopathy presented changes in the contractile behavior of type 2a fibers and compensatory adaptations in type 2b fibers. The results suggest that RT in combination with morphometric parameters provides data regarding muscle function in patients with myopathic disorders and can contribute to the establishment of therapeutic exercises.

Topics: Adenosine Triphosphatases; Creatine Kinase; Cross-Sectional Studies; Elbow Joint; Electromyography; Female; Humans; Male; Movement; Muscle Contraction; Muscle Fibers, Skeletal; Muscle Strength Dynamometer; Muscular Diseases; Statistics, Nonparametric; 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

This study investigated whether exercise-induced muscle damage (EIMD) resulted in changes to whole-body substrate utilisation during exercise performed during the subsequent 48 hours. Eight males (31 ± 6 years) performed 30 minutes of bench-stepping exercise. One leg performed eccentric contractions (Ecc) by lowering the body whilst the control leg performed concentric contractions (Con) by raising the body. On the two days following bench-stepping exercise participants performed measures of muscle function on an isokinetic dynamometer and undertook a bout of one leg cycling exercise, at two differing workloads, with the first workload (WL1) at 1.5 ± 0.25 W/kg and the second workload (WL2) at 1.8 ± 0.25 W/kg with each leg. Expired respiratory gases were collected during cycling to estimate whole body substrate utilisation. There were significant decrements in measures of muscular performance (isometric force, concentric and eccentric torque) and increased perception of soreness in Ecc compared with Con (P < 0.05). The effect of the Ecc treatment on substrate utilisation during one-legged cycling revealed a significant trial × time interaction with higher rates of CHO oxidation in the Ecc condition compared with Con that were further increased 48 hours later (P = 0.02). A significant treatment × time × effort interaction (P < 0.01) indicated the effect of the treatment altered as workload increased with higher rates of CHO oxidation occurring in WL2. This is consistent with greater reliance upon muscle glycogen. Suggesting that in EIMD, reductions in strength and increased feelings of soreness can be associated with greater reliance upon intramuscular CHO oxidation, than lipid, during subsequent concentric work.

Topics: Adult; Energy Metabolism; Exercise Test; Humans; Isometric Contraction; Lactates; Male; Muscle, Skeletal; Muscular Diseases; Spectrophotometry; Torque

Here, we test the hypothesis that continuous concentric exercise training renders skeletal muscles more susceptible to damage in response to eccentric exercise. Elite road cyclists (CYC; n = 10, training experience 8.1 ± 2.0 years, age 22.9 ± 3.7 years), long-distance runners (LDR; n = 10, 9.9 ± 2.3 years, 24.4 ± 2.5 years), and healthy untrained (UT) men (n = 10; 22.4 ± 1.7 years) performed 100 submaximal eccentric contractions at constant angular velocity of 60° s(-1). Concentric isokinetic peak torque, isometric maximal voluntary contraction (MVC), and electrically induced knee extension torque were measured at baseline and immediately and 48 h after an eccentric exercise bout. Muscle soreness was assessed and plasma creatine kinase (CK) activity was measured at baseline and 48 h after exercise. Voluntary and electrically stimulated knee extension torque reduction were significantly greater (p < 0.05) in UT than in LDR and CYC. Immediately and 48 h after exercise, MVC decreased by 32 % and 20 % in UT, 20 % and 5 % in LDR, and 25 % and 6 % in CYC. Electrically induced 20 Hz torque decreased at the same times by 61 and 29 % in UT, 40 and 17 % in LDR, and 26 and 14 % in CYC. Muscle soreness and plasma CK activity 48 h after exercise did not differ significantly between athletes and UT subjects. In conclusion, even though elite endurance athletes are more resistant to eccentric exercise-induced muscle damage than are UT people, stretch-shortening exercise-trained LDR have no advantage over concentrically trained CYC.

Topics: Adult; Bicycling; Electric Stimulation; Exercise; Humans; Male; Muscle Contraction; Muscle Fatigue; Muscle, Skeletal; Muscular Diseases; Plyometric Exercise; Range of Motion, Articular; Running; Torque; Young Adult

to investigate the association between muscle strength, biomechanical functional moments during everyday tasks and health-related quality of life (HRQoL) in older adults.. eighty-four healthy adults aged 60-88 years were tested. A torque dynamometer was utilised to measure muscle moments at the knee and hip joints. Functional assessment involved three-dimensional biomechanical analysis of gait, chair rise and sit-down, stair ascent and descent using an 8-camera VICON® system with Kistler force plates. HRQoL was assessed using the Short Form-36 (SF-36) questionnaire.. Spearman's correlation coefficient showed significant correlation (P < 0.001) between isometric strength and functional moments (r = 0.24-0.67). Muscle strength was significantly correlated with SF-36 scores, including physical functioning, bodily pain, vitality, social functioning and role emotional scores. Knee flexion moment was correlated with role physical, vitality, social functioning, role emotional, mental health and mental component scores (r = 0.24-0.40).. loss of muscle strength is associated with poorer functional ability and both are associated with reduced HRQoL. The reduction in HRQoL is considerable in the physical functioning domain. Cause and effect was not established but studies need to be undertaken to evaluate the benefits of strength training, functional activity training or increased participation in life.

Topics: Activities of Daily Living; Age Factors; Aged; Aged, 80 and over; Aging; Biomechanical Phenomena; Female; Health Status; Hip Joint; Humans; Isometric Contraction; Knee Joint; Male; Middle Aged; Muscle Strength; Muscle Strength Dynamometer; Muscle, Skeletal; Muscular Diseases; Quality of Life; Scotland; Surveys and Questionnaires; Torque; Video Recording

Alpha-actinin-3 (ACTN3) is an integral part of the Z line of the sarcomere. The ACTN3 R577X (rs1815739) polymorphism determines the presence or absence of functional ACTN3, which may influence the extent of exercise-induced muscle damage. This study aimed to compare the impact of, and recovery from, muscle-damaging eccentric exercise on subjects with or without functional ACTN3. Seventeen young men (20-33 years old), homozygous for the R (n = 9) or X (n = 8) alleles, performed two bouts of stretch-shortening exercise (50 drop jumps) two weeks apart. Muscle soreness, plasma creatine kinase (CK) activity, jump height, maximal voluntary isometric torque (MVC), peak concentric isokinetic torque (IT), and electrically stimulated knee extension torques at 20 and 100 Hz were measured at baseline and at a number of time points up to 14 days after each bout. There were no significant baseline differences between the groups. However, significant time point × genotype interactions were observed for MVC (p = 0.021) and IT (p = 0.011) for the immediate effect of eccentric exercise in bout 1. The RR group showed greater voluntary force decrements (RR vs. XX: MVC, -33.3% vs. -24.5%; IT, -35.9% vs. -23.2%) and slower recovery. A repeated-bout effect was clearly observed, but there were no differences by genotype group. The ACTN3 genotype modulates the response of muscle function to plyometric jumping exercise, although the differences are modest. The ACTN3 genotype does not influence the clearly observed repeated-bout effect; however, XX homozygotes recover baseline voluntary torque values faster and thus may be able to undertake more frequent training sessions.

Topics: Actinin; Adult; Biomechanical Phenomena; Exercise; Genotype; Homozygote; Humans; Male; Muscle, Skeletal; Muscular Diseases; Plyometric Exercise; Polymorphism, Genetic; Time Factors; Torque; Young Adult

The aim of this cross-sectional study was to concurrently assess musculo-articular stiffness (MAS) and muscle stiffness (MS) of the knee extensors in younger and older individuals.. Fourteen young (22.1 ± 3.0 years old) and 12 older (65.4 ± 5.7 years old) men were tested for maximal voluntary contraction (MVC), rate of torque development (RTD), muscle thickness, MAS, and MS of knee extensors.. MVC, RTD, and muscle thickness were higher in the younger group (288.6 vs. 194.3 Nm, 1319.5 vs. 787.0 Nm s(-1), 23.1 vs. 17.7 mm, respectively, P < 0.05). MAS normalized to the load supported (30% of MVC) was not different between groups (87.9 vs. 88.5 Nm(-1) kg(-1)), whereas the older group exhibited a higher level of normalized MS (23.2 vs. 18.6 Nm(-1) kg(-1), P < 0.05).. Determinants of MS have been highlighted along with their role in elevated MS. The unaltered level of MAS, which is functionally important in an aging population, might be achieved through a decrease in tendon stiffness.

Topics: Adult; Aged; Aging; Cross-Sectional Studies; Humans; Isometric Contraction; Knee Joint; Male; Middle Aged; Muscular Diseases; Quadriceps Muscle; Tendons; 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

The goal of this study was to determine if heart failure alters knee extensor muscle torque, power production or contractile velocity.. Heart failure patients (n=11; 70.4±4.3 yrs) and controls (n=11; 70.3±3.4 yrs) matched for age and sex were evaluated for knee extensor contractile performance under isometric and isokinetic conditions and body composition by dual energy X-ray absorptiometry. Additionally, we recruited sedentary to minimally active elderly controls to match heart failure patients for habitual physical activity and assessed activity levels using accelerometry.. Groups did not differ for total or regional body composition or average daily physical activity level. Despite similar muscle size and use, heart failure patients exhibited 21-29% lower (P<0.05 to P<0.01) isometric knee extensor torque throughout a range of knee angles, 15-33% lower (P=0.05 to P<0.01) peak concentric torque measured at various isokinetic speeds and corresponding reductions (P=0.05 to P<0.01) in peak power output. Expression of peak isokinetic torque data relative to isometric torque eliminated group differences, suggesting that impaired contractile function under dynamic conditions is explained by deficits in the force generating capacity of muscle. No group differences were found in the time required to reach target velocity during isokinetic contractions, an index of contractile velocity.. Because group differences in muscle torque were independent of age, sex, physical activity level and muscle size, our results suggest that muscle contractile dysfunction in these patients is likely attributable to the heart failure syndrome.

Topics: Aged; Cachexia; Disability Evaluation; Female; Heart Failure; Humans; Isometric Contraction; Knee Joint; Male; Motor Activity; Muscle, Skeletal; Muscular Diseases; Oxygen Consumption; Sedentary Behavior; Torque

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

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

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

To determine the relationships between two tests of stepping ability (the maximal step length (MSL) and rapid step test (RST)) and standard tests of standing balance, gait, mobility, and functional impairment in a group of at-risk older adults.. Cross-sectional study.. University-based laboratory.. One hundred sixty-seven mildly balance-impaired older adults recruited for a balance-training and fall-reduction program (mean age 78, range 65-90).. Measures of stepping maximally (MSL, the ability to maximally step out and return to the initial position) and rapidly (RST, the time taken to step out and return in multiple directions as fast as possible); standard measures of balance, gait, and mobility including timed tandem stance (TS), tandem walk (TW, both timing and errors), timed unipedal stance (US), timed up and go (TUG), performance oriented mobility assessment (POMA), and 6-minute walk (SMW); measures of leg strength (peak knee and ankle torque and power at slow and fast speeds); self-report measures of frequent falls (>2 per 12 months), disability (Established Population for Epidemiologic Studies of the Elderly (EPESE) physical function), and confidence to avoid falls (Activity-specific Balance Confidence (ABC) Scale). Spearman and Pearson correlation, intraclass correlation coefficient, logistic regression, and linear regression were used for data analysis.. MSL consistently predicted a number of self-report and performance measures at least as well as other standard balance measures. MSL correlations with EPESE physical function, ABC, TUG, and POMA scores; SMW; and peak maximum knee and ankle torque and power were at least as high as those correlations seen with TS, TW, or US. MSL score was associated with the risk of being a frequent faller. In addition, the six MSL directions were highly correlated (up to 0.96), and any one of the leg directions yielded similar relationships with functional measures and a history of falls. Relationships between RST and these measures were relatively modest.. MSL is as good a predictor of mobility performance, frequent falls, self-reported function, and balance confidence as standard stance tests such as US. MSL simplified to one direction may be a useful clinical indicator of mobility, balance, and fall risk in older adults.

Topics: Accidental Falls; Age Factors; Aged; Aged, 80 and over; Cross-Sectional Studies; Female; Frail Elderly; Gait; Geriatric Assessment; Humans; Leg; Locomotion; Logistic Models; Male; Muscular Diseases; Postural Balance; Predictive Value of Tests; Risk Factors; Statistics, Nonparametric; Time Factors; Torque; Walking

Research investigating the most effective management of Achilles tendon injury has been limited by a lack of reliable outcome measurements. Calf strength may be a valid outcome measure, not only in terms of identifying possible risk factors for reoccurrence of rupture, but also as an indicator of recovery. Isokinetic dynamometry has been suggested as an effective tool for measuring the torque of the calf muscles. Such measurements have demonstrated high reliability for the assessment of calf muscle torque in healthy subjects. However, there are no published data to demonstrate the reliability of isokinetic dynamometry in subjects with pathology in the Achilles tendon. The purpose of this study was to assess the inter- and intraobserver reliability of isokinetic dynamometry for assessing plantarflexion torque following Achilles tendon rupture.. Two independent observers used the Kin-com Dynamometer to measure the torque of the plantarflexors in 22 subjects 6 months after unilateral rupture of the Achilles tendon. Twelve subjects had been managed operatively and 10 nonoperatively. Subjects were placed in the prone position with the knee extended. Measurements of peak torque, average torque, and total work were made for both concentric and eccentric plantarflexion movements at 60 degrees per second.. Intraclass correlation coefficients were used to calculate reliability of measurements both within and between observers. Reliability was slightly greater on the healthy side (0.74-0.92 ICC) in comparison with the injured side (0.74-0.89 ICC).. The results of this study suggest that isokinetic dynamometry provides a reliable method of measuring the torque of the plantarflexors following rupture of the Achilles tendon, with levels of reliability comparable with those from healthy subjects. The study concludes that this would be a valuable and reliable outcome measure for use in clinical trials.

Topics: Achilles Tendon; Adult; Aged; Female; Foot; Humans; Male; Middle Aged; Muscle Contraction; Muscular Diseases; Observer Variation; Reproducibility of Results; Rupture, Spontaneous; Tendon Injuries; Torque

We investigated the frequency dependence of motor thresholds over the frequency range 1 kHz to 25 kHz. Alternating current (AC), ramped in intensity, was applied transcutaneously, and the induced wrist extensor torque was measured. Plots of log torque versus stimulus voltage were used to accurately determine thresholds. Three kinds of sinusoidal AC stimuli were compared: continuous, 10 ms bursts at 50 Hz, and 50-Hz single-cycle. Differences were attributed to summation of subthreshold depolarizations. The variation in relative thresholds (continuous/single-cycle and burst/single-cycle) indicates that summation occurs more efficiently at higher kHz frequencies. The observed frequency and waveform dependence provides evidence for high-frequency nerve fiber firing rates and fiber dropout when continuous or modulated AC is used, with the effects increasing with AC frequency. The form of the motor response evoked at high frequencies has features that suggest that frequencies above 10-kHz have little or no useful clinical role in rehabilitation procedures.

Topics: Adult; Electric Conductivity; Electric Stimulation Therapy; Female; Humans; Male; Middle Aged; Motor Neurons; Muscle Contraction; Muscular Diseases; Torque; Wrist Joint

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