vendex and Body-Weight

The purpose of this investigation was to determine the effects of 3 d of creatine supplementation on thermoregulation and isokinetic muscular performance.. Fourteen males performed two exercise bouts following 3 d of creatine supplementation and placebo. Subjects exercised for 60 min at 60-65% of VO2max in the heat followed by isokinetic muscular performance at 60, 180, and 300°·s(-1). Dependent variables for pre- and postexercise included nude body weight, urine specific gravity, and serum creatinine levels. Total body water, extracellular water and intracellular water were measured pre-exercise. Core temperature was assessed every 5 min during exercise. Peak torque and Fatigue Index were used to assess isokinetic muscular performance.. Core temperature increased during the run for both conditions. Total body water and extracellular water were significantly greater (P<0.05) following creatine supplementation. No significant difference (P>0.05) was found between conditions for intracellular water, nude body weight, urine specific gravity, and serum creatinine. Pre-exercise scores for urine specific gravity and serum creatinine were significantly less (P<0.05) versus post-exercise. No significant differences (P>0.05) were found in peak torque values or Fatigue Index between conditions for each velocity. A significant (P<0.05) overall velocity effect was found for both flexion and extension. As velocity increased, mean peak torque values decreased.. Three d of creatine supplementation does not affect thermoregulation during submaximal exercise in the heat and is not enough to elicit an ergogenic effect for isokinetic muscle performance following endurance activity.

Topics: Adult; Body Temperature Regulation; Body Weight; Creatine; Dehydration; Dietary Supplements; Double-Blind Method; Exercise; Exercise Test; Heart Rate; Humans; Male; Muscle Contraction; Muscle, Skeletal; Physical Exertion; Torque

A reduced range of hip internal rotation is associated with increased peak anterior cruciate ligament (ACL) strain and risk for injury. It is unknown, however, whether limiting the available range of internal femoral rotation increases the susceptibility of the ACL to fatigue failure.. Risk of ACL failure is significantly greater in female knee specimens with a limited range of internal femoral rotation, smaller femoral-ACL attachment angle, and smaller tibial eminence volume during repeated in vitro simulated single-leg pivot landings.. Controlled laboratory study.. A custom-built testing apparatus was used to simulate repeated single-leg pivot landings with a 4×-body weight impulsive load that induces knee compression, knee flexion, and internal tibial torque in 32 paired human knee specimens from 8 male and 8 female donors. These test loads were applied to each pair of specimens, in one knee with limited internal femoral rotation and in the contralateral knee with femoral rotation resisted by 2 springs to simulate the active hip rotator muscles' resistance to stretch. The landings were repeated until ACL failure occurred or until a minimum of 100 trials were executed. The angle at which the ACL originates from the femur and the tibial eminence volume were measured on magnetic resonance images.. The final Cox regression model (P = .024) revealed that range of internal femoral rotation and sex of donor were significant factors in determining risk of ACL fatigue failure. The specimens with limited range of internal femoral rotation had a failure risk 17.1 times higher than did the specimens with free rotation (P = .016). The female knee specimens had a risk of ACL failure 26.9 times higher than the male specimens (P = .055).. Limiting the range of internal femoral rotation during repetitive pivot landings increases the risk of an ACL fatigue failure in comparison with free rotation in a cadaveric model.. Screening for restricted internal rotation at the hip in ACL injury prevention programs as well as in individuals with ACL injuries and/or reconstructions is warranted.

Topics: Anterior Cruciate Ligament; Anterior Cruciate Ligament Injuries; Biomechanical Phenomena; Body Weight; Cadaver; Fatigue; Female; Femur; Humans; Knee Injuries; Knee Joint; Male; Middle Aged; Muscle, Skeletal; Risk Factors; Rotation; Tibia; Torque

Little is known about the effects of total knee replacement surgery on the contributions of individual joint moments to the total support moment. A better understanding of these effects may enhance rehabilitation protocols and determine factors related to long-term surgical outcome.. Twenty-one subjects with total knee replacement and 21 controls performed level walking and stair ascent at two testing periods, pre- and 6 months post-surgery. Variables studied included gait velocity, stride length, knee flexion angle, net joint moments of the hip, knee and ankle, and total support moment. Data were analyzed at the first peak vertical ground reaction force.. For level walking, the total support moment, knee extensor moment, and knee flexion angle of total knee replacement patients were less than controls at post-surgery. For stair ascent, the patient group total support moment, ankle plantarflexor moment, and knee flexion angle were less than controls at both testing periods, while knee extensor moment was less than controls at post-surgery. Extensor synergies of the total knee replacement patients revealed less knee and more hip contributions during level walking and larger hip contributions during stair ascent to the total support moment than controls at both testing periods.. A feature of total knee replacement gait, pre- and post-surgery, is a stiff knee attitude which may serve to protect the quadriceps. The larger hip extensor contribution to the total support moment observed in the patients may compensate for the diminished knee extensor contribution during level walking and stair ascent.

Topics: Adaptation, Physiological; Aged; Arthroplasty, Replacement, Knee; Body Weight; Female; Gait; Humans; Leg; Male; Muscle Contraction; Torque; Walking; Weight-Bearing

To investigate the relationships among hip joint moments produced during functional activities and hip bone mass in sedentary older adults.. Eight male and eight female older adults (70-85 yr) performed functional activities including walking, chair sit-stand-sit, and stair stepping at a self-selected pace while instrumented for biomechanical analysis. Bone mass at proximal femur, femoral neck, and greater trochanter were measured by dual-energy X-ray absorptiometry. Three-dimensional hip moments were obtained using a six-camera motion analysis system, force platforms, and inverse dynamics techniques. Pearson's correlation coefficients were employed to assess the relationships among hip bone mass, height, weight, age, and joint moments. Stepwise regression analyses were performed to determine the factors that significantly predicted bone mass using all significant variables identified in the correlation analysis.. Hip bone mass was not significantly correlated with moments during activities in men. Conversely, in women bone mass at all sites were significantly correlated with weight, moments generated with stepping, and moments generated with walking (p<0.05 to p<0.001). Regression analysis results further indicated that the overall moments during stepping independently predicted up to 93% of the variability in bone mass at femoral neck and proximal femur; whereas weight independently predicted up to 92% of the variability in bone mass at greater trochanter.. Submaximal loading events produced during functional activities were highly correlated with hip bone mass in sedentary older women, but not men. The findings may ultimately be used to modify exercise prescription for the preservation of bone mass.

Topics: Activities of Daily Living; Aged; Aged, 80 and over; Aging; Body Weight; Bone Density; Female; Femur; Hip Joint; Humans; Male; Movement; Muscle Contraction; Organ Size; Radiography; Statistics as Topic; Stress, Mechanical; Torque; Weight-Bearing

Different methods for adjusting muscle strength ( S) to normalise for differences in various estimates of body size [such as body mass ( m) or, infrequently, some other anthropometrical measurements] have been either proposed or applied when presenting the results of muscle function tests in various medical, ergonomic, and sport related studies. However, the fact that the relationship between S and body size may differ when muscle torque (measured using a standard isokinetic apparatus) and muscle force (measured using a dynamometer) are recorded has not been taken into account. To address this problem, we tested both muscle force and muscle torque under isometric conditions in six different muscle groups. The relationship assumed between S and m was S=k.m(b) and, according to a simple mechanical model based on geometrical similarity we developed, the exponential parameter b would be expected to equal 1.00 and 0.67 for torque and force, respectively. The experimentally obtained values for the parameter b were higher for muscle torque than for muscle force in five out of the six muscle groups tested ( P=0.068; Wilcoxon matched pairs test). Despite a relatively wide scatter, the mean (SD) values were also close to those predicted, being b=0.67 (0.19) (corresponding to the allometric scaling method) and b=1.02 (0.34) (corresponding to the ratio standards method) for muscle force and for muscle torque, respectively. Therefore, we concluded that the ratio standards and allometric scaling should be employed to adjust S for body size when muscle torque and muscle force, respectively, are tested.

Topics: Adult; Anthropometry; Body Constitution; Body Weight; Elbow; Exercise; Exercise Test; Hip; Humans; Knee; Male; Middle Aged; Models, Biological; Muscle Contraction; Muscle, Skeletal; Regression Analysis; Reproducibility of Results; Sensitivity and Specificity; Stress, Mechanical; Torque

This study evaluates the reliability of isokinetic testing of the knee flexors and extensors in children with cerebral palsy (CP). Twelve children (seven girls, five boys), aged 9 to 15 years, participated in this study. The children's strength was measured bilaterally, using a dynamometer. Each participant was tested twice at an interval of 1 week. During each session, the participant performed five consecutive cycles of knee extension and flexion. Testing velocity was set at 90 degrees/s, and the range of motion was 80 degrees, starting with the knee flexed at 80 degrees and ending in full extension. The measured variable was the peak torque. Reliabilities were determined using intraclass coefficient (ICC) with two-way ANOVA model. The ICCs for individual sessions range from 0.90 to 0.99. ICCs for the eight repetitions over the two sessions range from 0.95 to 0.98. The findings indicate that measuring isokinetic strength in the tested population is highly reliable and should be considered in rehabilitation protocols.

Topics: Adolescent; Analysis of Variance; Body Weight; Cerebral Palsy; Child; Female; Humans; Isotonic Contraction; Knee; Male; Muscle, Skeletal; Reproducibility of Results; Tensile Strength; Torque

Tennis practice requires a lot of technical, physical and mental qualities that have to be trained from the youngest age. The important number of hours spent on the court can lead, medium-to-long term to strength or flexibility adaptations, even in the youngest players. The current study aimed to explore the developmental consequences of repetitively playing tennis on shoulder range of motion and shoulder rotators' strength in elite male and female tennis players.. Eigthy four painfree elite tennis players were assessed during preseason between 2009 and 2019. Clinical assessment included internal and external rotation range of motion and forward shoulder posture while maximal internal and external rotators strength were assessed with an isokinetic dynamometer in concentric and in eccentric modes (at 60°/s and 240°/s).. In male players, growth and maturation induced an increase in forward shoulder posture. Absolute peak torque and bodyweight peak torque of internal and external rotators in concentric and eccentric mode were also significantly increased during with age while ER/IR concentric ratios were significantly decreased. In the female players, only absolute peak torque of internal and external rotators in concentric mode and eccentric strength of external rotators were significantly influenced by the development.. Specific adaptations were found in male and female players with age and practice. The important variability in the results within the different age categories and the gender strengthens the importance of regular screening (and isokinetic evaluations) in young tennis players in order to highlight potential atypical profiles, which could have a negative influence on performance or increase the risk of injuries during the development of the player.

Topics: Body Weight; Female; Humans; Male; Muscle Strength; Range of Motion, Articular; Shoulder; Shoulder Joint; Tennis; Torque

Few investigations have evaluated isokinetic torque after a period of weight loss in wrestlers. Thus, the current study sought to investigate the effects of gradual weight loss in the precompetitive period on isokinetic peak torque in the upper and lower limbs and body composition in wrestling athletes.. Eight elite athletes participated in the study (mean age 20.8±3.1 years). The athletes visited the laboratory on 2 occasions: during the period of weight maintenance (baseline) and during weight loss, in the precompetitive period (post). The variables analyzed were body composition through air displacement plethysmography (BOD POD) and peak torque (PT) of knee flexion and extension movements, and internal and external shoulder rotation in concentric action, at speeds of 60°/s and 180°/s, determined using an isokinetic dynamometer (Biodex Medical Systems; Shirley, NY, USA).. A significant decrease was observed in body composition values, except lean mass. No significant differences were observed in the PT of the movements analyzed: Shoulder internal rotation (60°/s P=0.825; 180°/s P=0.245) and external rotation (60°/s P=0.149; 180°/s P=0.163) and knee extension (60°/s P=0.086; 180°/s P=0.630) and flexion (60°/s P=0.310; 180°/s P=0.239).. Gradual weight loss did not affect the production of torque in the wrestlers before a competition. In addition, gradual weight loss contributed to a reduction in body fat, associated with an increase in percentage lean body mass.

Topics: Adipose Tissue; Adolescent; Adult; Athletes; Body Composition; Body Weight; Female; Humans; Male; Muscle Strength; Rotation; Shoulder; Torque; Weight Loss; Wrestling; Young Adult

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

Obesity is becoming more common in the world. This causes various health problems, especially musculoskeletal disorders. Previous studies have examined the kinematic effects of increasing weight on joints. However, the mechanical effects of movement patterns have not yet been described. The aim of this study was to investigate joint torques in sit-to-stand movement in teenagers with a range of body mass indices (BMI).. 20 participants (12-17 years old) participated the study. They were divided into 4 groups according to BMI. Participants performed sit-to-stand movements and the video was captured. Angular displacement, angular velocity, and angular acceleration were calculated for each joint. A four-degree-of-freedom link-segment model was created for a dynamic analysis of sit-to-stand. Joint torques were calculated using the inverse dynamic method.. Overweight increases joint torques in hips, knees, and ankles. In obese participants with a BMI 36% higher than normal-weight participants, joint torques in hips, knees, and ankles were higher by 46, 48, and 33%, respectively. In underweight participants with a BMI 21% lower than normal-weight participants, joint torques in neck, hip, knee, and ankle were lower by 20, 30, 17, and 7%, respectively.. Overweight participants have a different sit-to-stand movement pattern. Movement differences and overweight may cause an overload on joints.

Topics: Adolescent; Biomechanical Phenomena; Body Weight; Child; Hip Joint; Humans; Knee Joint; Movement; Posture; Torque

The objective of this study is to investigate the association between muscle function, body composition, and metabolic control in adults with type 2 diabetes mellitus (DM2).. Forty-eight individuals with DM2 were divided into four groups according to the severity of obesity (body mass index [BMI]: lean [LN, n = 10], overweight [OW, n = 16], obese class I [OBI, n = 15], and obese class II [OBII, n = 7]). Absolute peak torque (TQ), relative peak torque (TQ/body weight [BW]), total work (TW), and fatigue index (FI) were assessed by means of an isokinetic dynamometer during concentric knee extensor contraction. Spearman's correlation coefficients were used to estimate the association between measurements.. Although OBII had higher insulin levels than both LN and OW groups, no significant differences were found between groups for TQ, TQ/BW, TW, and FI, as well as between metabolic variables and muscle measurements. There was a positive correlation between BMI and TQ (r. Metabolic variables do not correlate with muscle strength and endurance in DM2. However, severity of obesity measured by the BMI is positively associated with muscle force-generating capacity and endurance.

Topics: Aged; Anthropometry; Body Composition; Body Mass Index; Body Weight; Diabetes Mellitus, Type 2; Female; Humans; Knee Joint; Male; Muscle Strength; Muscle, Skeletal; Obesity; Risk Factors; Torque

The purpose of this study was to use polynomial regression analyses to examine the torque- and power-velocity relationships and calculate and compare the vertices of these nonlinear models, and how they relate to measurements of muscle size and maximal strength, between male and female children and adolescents during maximal isokinetic leg extension muscle actions. Sixteen children (n = 8 males, n = 8 females) and 22 adolescents (n = 11 males, n = 11 females) participated in this study. Measurements of growth included age, maturity offset, height, body mass, fat-free mass, and quadriceps femoris muscle cross-sectional area (CSA). Participants completed maximal voluntary isometric contractions (MVICs) of the leg extensors and maximal voluntary isokinetic leg extensions at 60, 120, 180, 240, and 300°·s

Topics: Adolescent; Aging; Biomechanical Phenomena; Body Height; Body Weight; Child; Female; Humans; Isometric Contraction; Leg; Male; Muscle Strength; Nonlinear Dynamics; Quadriceps Muscle; Torque

One of the possible mechanisms leading to secondary impingement syndrome may be the strength imbalance of shoulder rotators which is known as functional control ratio (FCR). The FCR is a ratio dividing the eccentric peak torque of the external rotators by the concentric peak torque of the internal rotators. Previous studies have focused on the reproducibility and reliability of isokinetic assessment, but there is little information on the influence of variable shoulder positions on FCR.. To compare shoulder FCR across 3 different shoulder abduction positions during isokinetic assessment.. Cross-sectional study.. Biomechanics laboratory.. Thirty-one healthy young university students (age 22.35 [0.95] y, weight 60.52 [9.31] kg, height 168.23 [9.47] cm).. The concentric peak torque of internal rotators and eccentric peak torque of external rotators of right shoulder were measured on an isokinetic dynamometer.. Concentric peak torque of the internal rotators and eccentric peak torque of the external rotators, measured using an isokinetic dynamometer.. The concentric peak torque of internal rotators was significantly lower at 120° shoulder abduction compared with other positions (P < .001). The FCR was significantly higher at 120° shoulder abduction than 90° (P = .002) or 60° (P < .001) shoulder abduction because of the lower concentric peak torque. No significant difference was found in the FCR between the other 2 shoulder positions (P = .14).. Shoulder position variations may influence FCR because of weakness of the internal rotators. Rehabilitation and injury prevention training programs should specifically focus on strengthening the internal rotators at more elevated angles of shoulder abduction.

Topics: Body Weight; Cross-Sectional Studies; Female; Humans; Kinetics; Male; Muscle Weakness; Pectoralis Muscles; Posture; Reproducibility of Results; Rotator Cuff; Shoulder; Shoulder Joint; Statistics, Nonparametric; Torque; Young Adult

Alterations in throwing mechanics have been identified as a risk factor for overuse injuries in baseball players. Glenohumeral internal rotation deficit (GIRD) has been found to adversely affect throwing mechanics, but the effect of GIRD on medial elbow torque is unclear.. To investigate the relationship between GIRD and medial elbow torque in high school-aged baseball pitchers.. Descriptive laboratory study.. High school baseball pitchers (14-18 years old) were recruited for participation in this study. Players' height, weight, body mass index, and arm measurements were recorded as well as shoulder and elbow range of motion measurements. GIRD was calculated from the difference between dominant and nondominant shoulder internal rotation. Participants then pitched 5 fastballs at maximum effort while wearing a wireless sensor that recorded elbow torque, arm slot, arm speed, shoulder rotation, and ball velocity. Principal component analysis was performed to determine which variables were associated with elbow torque or ball velocity.. Twenty-three high school pitchers participated in this study; 35% (n = 8) of participants exhibited GIRD of at least 20°. The mean GIRD was 15.3°± 11.2° and was not a predictor of medial elbow torque (. In high school baseball pitchers, GIRD was not associated with medial elbow torque during the pitching motion. Instead, ball velocity, player age, and player height carried greater significance.. This study suggests that high school pitchers with GIRD do not have an inherently greater risk for increased medial elbow torque during the throwing motion. It is recommended that pitchers instead assess their ball velocity to evaluate for relative differences in medial elbow torque.

Topics: Adolescent; Baseball; Biomechanical Phenomena; Body Height; Body Mass Index; Body Weight; Cumulative Trauma Disorders; Elbow Injuries; Elbow Joint; Humans; Male; Range of Motion, Articular; Risk Factors; Rotation; Shoulder Injuries; Shoulder Joint; Torque; Young Adult

The associations among lower extremity functional performance and quality of life in obese youth are unknown. The aims of this study were to compare lower extremity strength, lower extremity functional performance, and health related quality of life between obese and healthy-weight youth and evaluate the relationships between lower extremity performance and health related quality of life in obese youth. Twenty obese and 20 age and sex matched healthy-weight youth were recruited. Peak torque of the major lower extremity muscles were measured. Functional performance was measured with single leg hop and single leg balance tests. The Paediatric Quality of Life questionnaire's physical and psychosocial health subscales were used. Paired t-tests and multiple regression analyses were performed. Obese youth demonstrated decreased peak torque in all muscles measured (P < 0.05), poorer functional performance (P < 0.05), and worse physical health related quality of life (P < 0.05) compared to healthy-weight youth. Lower extremity functional performance was associated with aspects of quality of life in the obese group (P = 0.002), but not in the healthy-weight group (P < 0.05). These results may assist in encouraging best practices in the promotion of exercise, physical activity, and quality of life in obese youth.

Topics: Adolescent; Body Weight; Child; Exercise; Exercise Test; Female; Humans; Lower Extremity; Male; Muscle Strength; Muscle, Skeletal; Pediatric Obesity; Physical Functional Performance; Quality of Life; Regression Analysis; Sexual Development; Surveys and Questionnaires; Torque

Aging brings about challenges in the ability to recover balance through protective stepping, especially in the lateral direction. Previous work has suggested that lateral protective stepping during weight transfer may be affected by impaired muscle composition and performance of the hip abductors (AB) in older adults. Hence, this study investigated the influence of hip abductor-adductor (AB-AD) neuromuscular performance on the weight transfer phase of lateral protective stepping in younger and older adults. Healthy younger (n = 15) and older adults (n = 15) performed hip AB-AD isometric maximal voluntary contractions (IMVC). Lateral balance perturbations were applied via motorized waist-pulls. Participants were instructed to recover their balance using a single lateral step. Kinetic, kinematic and electromyographic (EMG) data were analyzed during the weight transfer phase. In the hip IMVC task, older adults showed reduced peak AB-AD torque, AB rate of torque development and AB-AD rate of EMG neuromuscular activation (RActv). During the lateral balance perturbations, older individuals had a lower incidence of lateral steps, reduced hip AB-AD RActv and delayed weight transfer. However, several outcomes were larger in the older group, such as, center of mass momentum at step onset, step-side peak rate of vertical force development, hip AB net joint torque, and power. Although older adults had greater hip muscular output during the weight transfer phase, their lateral balance recovery was still impaired. The reduced maximal hip AB-AD capacity, especially RActv, may have been a greater contributor to this impairment, as it affects the ability to generate rapid force, crucial for balance recovery.

Topics: Aged; Aging; Biomechanical Phenomena; Body Weight; Female; Hip Joint; Humans; Isometric Contraction; Male; Mechanical Phenomena; Movement; Muscle, Skeletal; Nervous System Physiological Phenomena; Postural Balance; Torque

The primary purpose of this investigation was to determine whether strength-matched men and women exhibit a different magnitude and ratio of leg muscle activity during a maximal voluntary isometric squat. The secondary purpose was to assess the effect of normalization method on differences in strength between men and women. Thirty-two men (n = 16) and women (n = 16) were successfully strength-matched (≤10% difference) by maximal force produced during an isometric squat (IS) when normalized to body weight. Subjects first performed a maximal isometric knee extension (IKE) and knee flexion (IKF) followed by the IS and muscle activity (EMG

Topics: Body Mass Index; Body Weight; Electromyography; Female; Hamstring Muscles; Humans; Isometric Contraction; Knee; Leg; Male; Muscle Strength; Quadriceps Muscle; Resistance Training; Sex Factors; Task Performance and Analysis; Torque

This study investigated differences in the declines of isometric strength in hip abductors and adductors versus knee extensors across four different age groups (n = 31: 11.2 ± 1.0 y, n = 30: 23.1 ± 2.7 y, n = 27: 48.9 ± 4.4 y, and n = 33: 70.1 ± 4.2 y) with a total of 121 female subjects. As a starting point, we assumed that, during their daily activities, elderly people would use their leg stabilizers less frequently than their leg primary movers as compared to younger people. Given that muscle strength decreases in the course of the aging process, we hypothesized that larger strength declines in hip abductors and hip adductors as compared to knee extensors would be detected across age. Maximal isometric force for these muscle groups was assessed with a digital hand-held dynamometer. Measurements were taken at 75% of the thigh or shank length and expressed relative to body weight and lever arm length. Intratester reliability of the normalized maximal torques was estimated by using Cronbach's alpha and calculated to be larger than 0.95. The obtained results indicate a clearly more pronounced strength decline in hip abductors and hip adductors across age than in the knee extensors. Therefore, a particular need for strength training of the lower extremity stabilizer muscles during the aging process is implied.

Topics: Accidental Falls; Adolescent; Adult; Aged; Body Weight; Child; Female; Humans; Isometric Contraction; Knee; Knee Joint; Leg; Middle Aged; Muscle Strength; Muscle Strength Dynamometer; Muscle, Skeletal; Reproducibility of Results; Torque; Young Adult

We present a novel control method for an omnidirectional robotic platform for gait training. This mobile platform or "walker" provides trunk support and allows unrestricted motion of the pelvis simultaneously. In addition to helping the user maintain balance and preventing falls, the walker combines two types of therapeutic intervention: forward propulsion of the trunk and partial body weight support (BWS). The core of the walker's control is an admittance controller that maximizes the platform's horizontal mobility by optimizing the virtual mass of the admittance model. Said mass represents the best tradeoff between a low-frequency oscillation mode that becomes more damped as the virtual mass decreases, and a high-frequency mode that becomes less damped simultaneously and hence could destabilize the system. Forward propulsion of the trunk is aided by a horizontal force that is modulated with the patient's gait speed and turning rate to ensure easy adaptation. BWS is provided by a second, independent admittance controller that generates a spring-like upward force. In an initial study, a stroke patient was able to walk stably in the platform, as evidenced by the absence of oscillations associated with an excessively low virtual mass. A progressive increase in the patient's self-selected speed, along with greater uniformity in the instantaneous velocity, suggest that forward propulsion was effective in compensating the patient's own propulsion deficit.

Topics: Body Weight; Chronic Disease; Feedback; Female; Gait; Humans; Linear Models; Stroke; Stroke Rehabilitation; Torque

Human joint impedance describes the dynamic relationship between perturbation induced change in position and the resulting response torque. Understanding the natural regulation of ankle impedance during locomotion is necessary to discern how humans interact with their environments, and provide a foundation for the design of biomimetic assistive devices and their control systems. This paper estimates ankle impedance during terminal stance phase of walking using a parametric model consisting of stiffness, damping, and inertia. The model accurately described ankle torque, accounting for 90% ± 7.7% of the variance. Stiffness was found to decrease from 3.7 to 2.1 Nm/rad/kg between 75% and 85% stance. Quasi-stiffness-the slope of the ankle's torque-angle curve-showed a similar decreasing trend but was significantly larger at the onset of terminal stance phase. The damping component of impedance was constant during terminal stance phase, and was increased relative to values previously reported during early and mid-stance phases, indicating an increase in damping in preparation for toe-off. Inertia estimates were consistent with previously reported inertia values for the human ankle. This paper bridges a gap in our understanding of ankle impedance during walking, and provides new insight into how ankle impedance is regulated during regions when substantial mechanical energy is added.

Topics: Adult; Algorithms; Ankle; Biomechanical Phenomena; Body Weight; Female; Healthy Volunteers; Humans; Male; Models, Theoretical; Robotics; Self-Help Devices; Torque; Walking; Young Adult

We compared the skeletal muscle hypertrophy resulting from isometric (Iso) or eccentric (Ecc) electrical stimulation (ES) training with different stimulation frequencies. Male Wistar rats were assigned to the Iso and Ecc groups. These were divided into three further subgroups that were stimulated at 10 Hz (Iso-10 and Ecc-10), 30 Hz (Iso-30 and Ecc-30), or 100 Hz (Iso-100 and Ecc-100). In experiment 1, the left plantarflexor muscles were stimulated every other day for 3 wk. In experiment 2, mammalian target of rapamycin complex 1 (mTORC1) signaling was investigated 6 h after one bout of ES. The contralateral right muscle served as a control (non-ES). Ecc contractions comprised forced dorsiflexion combined with ES. The peak torque and torque-time integral during ES were higher in the Ecc group than that in the Iso group in all stimulation frequencies examined. The gastrocnemius muscle weight normalized to body weight in ES side was increased compared with the non-ES side by 6, 7, and 17% in the Ecc-30, Iso-100, and Ecc-100 groups, respectively, with a greater gain in Ecc-100 than the Ecc-30 and Iso-100 groups. The p70S6K (Thr389) phosphorylation level was higher in the Ecc-30 and -100 than in the Iso-30 and -100 groups, respectively. The peak torque and torque-time integral were highly correlated with the magnitude of increase in muscle mass and the phosphorylation of p70S6K. These data suggest that ES-induced muscle hypertrophy and mTORC1 activity are determined by loading intensity and volume during muscle contraction independent of the contraction mode. NEW & NOTEWORTHY Eccentric contraction and high-frequency stimulation (HFS) are regarded as an effective way to increase muscle mass by electrical stimulation (ES) training. However, little is known about whether muscle hypertrophy is affected by contraction mode and stimulation frequency in ES training. Here, we provide the evidence that muscle hypertrophy and mammalian target of rapamycin complex 1 activity are determined by mechanical loading during contraction but not on the contraction mode itself, with a greater gain at HFS.

Topics: Animals; Body Weight; Electric Stimulation; Hypertrophy; Isometric Contraction; Male; Mechanistic Target of Rapamycin Complex 1; Muscle Proteins; Muscle, Skeletal; Myofibrils; Phosphorylation; Physical Conditioning, Animal; Rats, Wistar; Ribosomal Protein S6; Ribosomal Protein S6 Kinases; Ribosomal Protein S6 Kinases, 70-kDa; Torque

To establish reference values for new methods designed to quantitatively measure forearm torque and lifting strength and to compare these values with grip strength.. A total of 499 volunteers, 262 males and 237 females, aged 15 to 85 (mean, 44) years, were tested for lifting strength and forearm torque with the Kern and Baseline dynamometers. These individuals were also tested for grip strength with a Jamar dynamometer. Standardized procedures were used and information about sex, height, weight, hand dominance, and whether their work involved high or low manual strain was collected.. Men had approximately 70% higher forearm torque and lifting strength compared with females. Male subjects aged 26 to 35 years and female subjects aged 36 to 45 years showed highest strength values. In patients with dominant right side, 61% to 78% had a higher or equal strength on this side in the different tests performed. In patients with dominant left side, the corresponding proportions varied between 41% and 65%. There was a high correlation between grip strength and forearm torque and lifting strength. Sex, body height, body weight, and age showed a significant correlation to the strength measurements. In a multiple regression model sex, age (entered as linear and squared) could explain 51% to 63% of the total variances of forearm torque strength and 30% to 36% of lifting strength.. Reference values for lifting strength and forearm torque to be used in clinical practice were acquired. Grip strength has a high correlation to forearm torque and lifting strength. Sex, age, and height can be used to predict forearm torque and lifting strength. Prediction equations using these variables were generated.. Normative data of forearm torque and lifting strength might improve the quality of assessment of wrist and forearm disorders as well as their treatments.

Topics: Adolescent; Adult; Age Factors; Aged; Aged, 80 and over; Body Weight; Female; Forearm; Functional Laterality; Hand Strength; Humans; Lifting; Male; Middle Aged; Muscle Strength Dynamometer; Sex Factors; Torque; Young Adult

Risberg, MA, Steffen, K, Nilstad, A, Myklebust, G, Kristianslund, E, Moltubakk, MM, and Krosshaug, T. Normative quadriceps and hamstring muscle strength values for female, healthy, elite handball and football players. J Strength Cond Res 32(8): 2314-2323, 2018-This study presents normative values for isokinetic knee extension and flexion muscle strength tests in 350 elite, female, handball (n = 150) and football (n = 200) players. Isokinetic concentric muscle strength tests at 60°·sec were recorded bilaterally using a dynamometer. Peak torque (in Newton meter [N·m]), body mass normalized peak torque (N·m·kg), and hamstring to quadriceps ratio (H:Q ratio) for dominant and nondominant legs were recorded. The female elite players were 20.9 ± 4.0 years, started playing at the elite level at the age of 18.2 ± 2.7 years, with a mean of 9.7 ± 2.2 hours of weekly in-season training. Handball players demonstrated greater quadriceps muscle strength compared with football players (11.0%) (p < 0.001), also when normalized to body mass (4.1%) (p = 0.012), but not for weight-adjusted hamstring muscle strength. The H:Q ratio was higher on the dominant compared with the nondominant leg for handball players only (p = 0.012).The H:Q ratio was significantly lower for handball players (0.58) compared with football players (0.60) (p < 0.02). These normative values for isokinetic knee extension and flexion torques of healthy, elite, female handball and football players can be used to set rehabilitation goals for muscle strength after injury and enable comparison with uninjured legs. Significantly greater quadriceps muscle strength was found for handball players compared with football players, also when normalized to body mass.

Topics: Adolescent; Adult; Body Weight; Female; Hamstring Muscles; Humans; Knee Joint; Muscle Strength; Quadriceps Muscle; Range of Motion, Articular; Reference Values; Soccer; Torque; Young Adult

This study sought to analyze the extent of motor adaptation in ankle plantar flexors and dorsiflexors among older drivers during clinical isokinetic testing.. One hundred older adults (70.4±5.7 years) participated in two bilateral ankle plantar flexor and dorsiflexor isokinetic assessments at 30°/sec. Peak torque (PTQ), PTQ adjusted for body weight (PTQ/BW), and total work (TW) were analyzed.. On the dominant side, PTQ/BW and TW were significantly greater for the second plantar flexion test than were those for the first such test (p<0.001), whereas PTQ, PTQ/BW, and TW (p<0.001) were significantly greater for the second dorsiflexion test than were those for the first such test. On the non-dominant side, plantar flexion PTQ and TW were significantly lower for the second test than were those for the first test (p<0.001).. Older drivers demonstrated better performance with the dominant limb on the second test. The low variability in test execution showed the existence of a motor adaptation effect for the tested movements, despite the short recovery period between the assessments.

Topics: Adaptation, Physiological; Age Factors; Aged; Aging; Ankle Joint; Automobile Driving; Body Weight; Female; Humans; Male; Motor Activity; Muscle Contraction; Muscle Strength; Reference Values; Statistics, Nonparametric; Torque

Spasticity of the elbow was generally assessed by repeated passive stretch movement, including the modified Ashworth Scale (MAS) from physiotherapist, and biomechanics analysis of the movement. The MAS-based method depends on the subjective evaluations and the performance of biomechanics analysis assessment is affected by the individual difference. Therefore, the normalization to reduce the individual difference for the assessment of spasticity is very important. In this study, the elbow spasticity was assessed with MAS by one skillful physiotherapist and biomechanics measurements during repetitive passive isokinetic movements at velocity of 60 degree$/$second. 20 post-stroke patients with elbow spasticity caused by hemorrhagic cerebral damage were divided into three groups according to the MAS grades (MAS $=1, 1+$, 2). The torque and position were recorded when the patients extension their elbows passively. The mean stiffness and the mean torque features of the passive isokinetic were calculated. Two normalization factors for biomechanics analysis assessment were investigated: body weight normalization factor and maximum isometrics volunteer contraction normalization factor. Spearman correlation analysis was used to investigate the relationship between the features and spasticity grades. The results showed that the correlation between MAS and two biomechanics features (mean stiffness, mean torque) were significant improved. For mean stiffness feature, the correlation coefficients were $-0.313, -0.563$ and -0.603 individually for non-normalization, body weight normalization and maximum isometrics volunteer contraction normalization. For mean torque feature, the correlation coefficients were $-0.260, -0.523$ and -0.691, respectively. These results suggest that the normalization methods would be helpful for the assessment of spasticity in biomechanics and will be a necessary way of spasticity estimation in clinical methods.

Topics: Body Weight; Brain Injuries; Elbow; Elbow Joint; Female; Humans; Male; Movement; Muscle Spasticity; Range of Motion, Articular; Stroke; Torque

While body weight support (BWS) intonation is vital during conventional gait training of neurologically challenged subjects, it is important to evaluate its effect during robot assisted gait training. In the present research we have studied the effect of BWS intonation on muscle activities during robotic gait training using dynamic simulations.. Two dimensional (2-D) musculoskeletal model of human gait was developed conjointly with another 2-D model of a robotic orthosis capable of actuating hip, knee and ankle joints simultaneously. The musculoskeletal model consists of eight major muscle groups namely; soleus (SOL), gastrocnemius (GAS), tibialis anterior (TA), hamstrings (HAM), vasti (VAS), gluteus maximus (GLU), uniarticular hip flexors (iliopsoas, IP), and Rectus Femoris (RF). BWS was provided at levels of 0, 20, 40 and 60% during the simulations. In order to obtain a feasible set of muscle activities during subsequent gait cycles, an inverse dynamics algorithm along with a quadratic minimization algorithm was implemented.. The dynamic parameters of the robot assisted human gait such as joint angle trajectories, ground contact force (GCF), human limb joint torques and robot induced torques at different levels of BWS were derived. The patterns of muscle activities at variable BWS were derived and analysed. For most part of the gait cycle (GC) the muscle activation patterns are quite similar for all levels of BWS as is apparent from the mean of muscle activities for the complete GC.. Effect of BWS variation during robot assisted gait on muscle activities was studied by developing dynamic simulation. It is expected that the proposed dynamic simulation approach will provide important inferences and information about the muscle function variations consequent upon a change in BWS during robot assisted gait. This information shall be quite important while investigating the influence of BWS intonation on neuromuscular parameters of interest during robotic gait training.

Topics: Ankle Joint; Biomechanical Phenomena; Body Weight; Computer Simulation; Gait; Hip Joint; Humans; Knee Joint; Models, Theoretical; Muscle, Skeletal; Orthotic Devices; Robotics; Torque

The aim of this study was to examine the differences in body composition, strength and power of lower limbs, height of jump measured for the akimbo counter movement jumps, counter movement jump and spike jumps between deaf and hearing elite female soccer players.. Twenty deaf (age: 23.7±5.0 years, hearing loss: 96±13.9 dB) and 25 hearing (age: 20.3±3.8 years) participated in the study. Their WHR and BMI were calculated. Body fat was measured using the BIA method. The maximal power and height of jump were measured by force plate. Biodex dynamometer was used to evaluate isokinetic isometric strength of the hamstrings and quadriceps.. Significant differences between hearing and deaf soccer players in anthropometric values were for the waist and calf circumferences and the WHR index ( p < 0.01, effect size 0.24-0.79). Statistically significant differences were observed for flexion of the lower limb in the knee joint for the relative joint torque and relative power obtained for the angular velocity of 300 degˑs-1 for both lower limbs (p < 0.01, effect size 0.19-0.48) and for 180 degˑs-1 during flexion of the left limb (p = 0.02, effect size 0.13). The hearing female football players developed significantly greater MVC in all the cases. Statistically significant differences between deaf and hearing athletes were found for spike jump for maximal power (1828.6 ± 509.4 W and 2215.2 ± 464.5 W, respectively; p = 0.02, effect size 0.14).. Hearing impairment does not limit the opportunities for development of physical fitness in the population of deaf women.

Topics: Biomechanical Phenomena; Body Weight; Deafness; Female; Hearing; Humans; Muscle Contraction; Soccer; Torque; Young Adult

To verify the effect of Pilates exercises in a child with cerebral palsy (CP) with mild functional impairment.. We evaluated average peak torque of ankle and knee extensors/flexors using a Biodex System, using concentric active-assisted test. We also evaluated amplitude of anterior-posterior and of medial-lateral displacement of the CoP and area of oscillation during quite standing with a BERTEC platform. We applied Pilates exercises for eight weeks.. Peak torque/body weight of ankle and knee extensors/flexors of both affected and unaffected limbs increased after Pilates. Also, all kinetic variables decreased after Pilates' intervention. After one-month follow-up, isokinetic variable values were higher while kinetic variable values were lower than baseline values.. Pilates may be an important rehabilitation technique for children with CP that present mild deficits in motor structures and high functional level, especially when the aims are to improve muscle strength and postural control during quite standing.

Topics: Ankle; Biomechanical Phenomena; Body Weight; Cerebral Palsy; Child; Exercise Therapy; Female; Humans; Knee; Lower Extremity; Muscle Strength; Muscle, Skeletal; Paresis; Torque; Treatment Outcome

The goal of this study is to analyze the effects of hand grip training on shoulder joint internal rotation (IR)/external rotation (ER) peak torque for healthy people.. The research was conducted on 23 healthy adults in their 20 s-30 s who volunteered to participate in the experiment. Hand grip power test was performed on both hands of the research subjects before/after the test to study changes in hand grip power. Isokinetic machine was used to measure the concentric IRPT (internal rotation peak torque) and concentric ERPT (external rotation peak torque) at the velocity of 60°/sec, 90°/sec, and 180°/sec before/after the test. Hand grip training was performed daily on the subject's right hand only for four weeks according to exercise program. Finally, hand grip power of both hands and the maximum torque values of shoulder joint IR/ER were measured before/after the test and analyzed.. There was a statistically significant difference in the hand grip power of the right hand, which was subject to hand grip training, after the experiment. Also, statistically significant difference for shoulder ERPT was found at 60°/sec.. Hand grip training has a positive effect on shoulder joint IRPT/ERPT and therefore can help strengthen muscles around the shoulder without using weight on the shoulder. Consequently, hand grip training would help maintain strengthen the muscles around the shoulder in the early phase of rehabilitation process after shoulder surgery.

Topics: Adult; Body Weight; Exercise; Female; Hand Strength; Humans; Male; Physical Conditioning, Human; Range of Motion, Articular; Rotation; Shoulder Joint; Torque; Young Adult

We evaluated sciatic nerve impairment after eccentric contractions (ECs) in rat triceps surae.. Wistar rats were randomly assigned to different joint angular velocity: 180°/s (FAST), 30°/s (SLOW), or nontreated control (CNT). FAST and SLOW groups were subjected to multiple (1-4) bouts of 20 (5 reps, 4 sets) ECs. Nerve conduction velocity (NCV) and isometric tetanic ankle torque were measured 24 h after each ECs bout. We also assessed nerve morphology.. After 4 ECs bouts, NCVs and isometric torque in the FAST group were significantly lower than those in the CNT (NCV: 42%, torque: 66%; P < 0.05). After 4 bouts, average nerve diameter was significantly smaller in the FAST group [2.39 ± 0.20 μm vs. 2.69 ± 0.20 μm (CNT) and 2.93 ± 0.24 μm (SLOW); P < 0.05] than that in other two groups.. Chronic ECs with high angular velocity induce serious nerve damage. Muscle Nerve 54: 936-942, 2016.

Topics: Analysis of Variance; Animals; Ankle; Body Weight; Disease Models, Animal; Isometric Contraction; Male; Microscopy, Electron; Muscle, Skeletal; Myelin Sheath; Nerve Fibers; Neural Conduction; Organ Size; Rats; Rats, Wistar; Reaction Time; Sciatic Neuropathy; Torque

A stationary start modification to the Wingate Anaerobic Test (WAnT) has become increasingly common. The aim of the present study was to determine whether the traditional 85 g kg(-1) body weight (BW) load (TRAD), or an individualized optimal load (OPT), is more suitable for obtaining peak and mean power outputs (PPO and MPO, respectively) for a stationary start.. Twelve recreationally active males and 10 females (mean age 30 ± 9.1 and 25 ± 5.5 years, respectively) completed three trials. The first determined the OPT load and included a familiarization of the 30-s stationary start test, followed by two randomized sessions testing the OPT and TRAD loads during the 30-s stationary start test on separate days. For each test, measures of power (watts), time, and cadence were collected to determine PPO, MPO, rate of power decline (rPD) and time to peak power (TtPP). All power data were corrected for flywheel moment of inertia.. Results revealed significant differences between OPT and TRAD load settings for males (95.1 ± 10.7 and 85.06 ± 0.40 g kg(-1) BW; p = 0.008) but not for females (84.71 ± 8.72 and 85.2 ± 0.61 g kg(-1) BW; p = 0.813). Relative PPO was not different for OPT or TRAD loads for males (p = 0.485) or females (p = 0.488).. It is not necessary to use an OPT load setting to acquire maximal PO for a 30-s cycle test using a stationary start. Instead, the traditional 85 g kg(-1) BW loading is suitable for both males and females.

Topics: Adult; Body Weight; Ergometry; Exercise Test; Female; Humans; Male; Muscle, Skeletal; Physical Exertion; Torque; Young Adult

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

The aim of the study was to determine the anthropometric and fitness profiles of European half-heavyweight judokas by success in competition. For this purpose, we compared 5 international medalists (elite) with 5 national medalists (subelite). All male judokas won at least 1 medal in the half-heavyweight category during the previous 2 years. The testing in this cross-sectional study was performed during 4 days. All subjects underwent anthropometric assessment with body mass, height, skinfold, and limb circumference measures, and the body fat percentage was estimated by manual bioimpedance. The physical fitness evaluation consisted in peak torques for thigh and shoulder muscles, handgrip strength, high and long jumps, medicine ball throw, pull-ups, deadlift, bench press, deep squat, V[Combining Dot Above]O2max, Max Power, and Tokui Waza tests. The statistical analysis by the Student's t test showed significant differences for forearm and upper-arm circumferences, peak torques, pull-ups, bench press, deadlift, deep squat, V[Combining Dot Above]O2max, Max Power, and Tokui Waza tests. Our results showed that elite judokas have a superior fitness profile than subelite athletes from the half-heavyweight category. Moreover, elite judokas seem to have a higher arm muscle mass than subelite athletes but a similar body fat percentage. This study could be of interest for judo coaches with athletes competing in the half-heavyweight category, as some tests that discriminate by judo success for this specific weight category are described. Few studies analyze anthropometric and fitness profiles in half-heavyweight male judokas, so additionally our results can be used as a reference for coaches, athletes, and scientists.

Topics: Adiposity; Adult; Arm; Body Height; Body Weight; Body Weights and Measures; Cross-Sectional Studies; Exercise Test; Forearm; Hand Strength; Humans; Male; Martial Arts; Muscle, Skeletal; Oxygen Consumption; Physical Fitness; Shoulder; Skinfold Thickness; Thigh; Torque; Young Adult

The aim of this study was to investigate the association between dietary protein (PRO) intake and maximal and rapid strength of the leg flexors in blue collar (BC) working men. Twenty-four young (age, 23.2 ± 2.1 years) and 19 older (age, 52.8 ± 5.2 years) men employed in BC occupations completed a 3-day dietary record and isometric strength testing of the leg flexors. Food logs were analyzed for total PRO (TPRO) and essential amino acid (EAA) intake. Rapid and maximal strength capacities were examined from the rate of torque development at 50 milliseconds and peak torque of the torque-time curves, respectively. Pearson correlations and partial correlations were used to examine the relationships between TPRO and EAA intake on strength variables. Peak torque was positively correlated to TPRO and EAA intake in the young (r = 0.439 and r = 0.431; P < .05) and older (r = 0.636 and r = 0.605; P < .01) men, and rate of torque development at 50 milliseconds was correlated to TPRO and EAA intake in the young (r = 0.512 and r = 0.310; P = .01) and older (r = 0.662 and r = 0.665; P < .01) men, respectively. There were no relationships (P > .05) between TPRO and strength variables when controlling for EAA intake. Total PRO intake explained 20 to 44% of the variance in rapid and maximal strength for both age groups. Essential amino acid intake was largely responsible for the positive relationship between PRO intake and strength. Across young and older BC working male populations, PRO consumption was associated with both maximal and explosive strength capacities of the leg flexors muscle group.

Topics: Adult; Amino Acids, Essential; Body Mass Index; Body Weight; Cross-Sectional Studies; Dietary Proteins; Humans; Leg; Male; Middle Aged; Muscle Strength; Muscle, Skeletal; Nutrition Assessment; Occupations; Torque; Young Adult

The purpose of this study was to determine the relative contributions of isokinetic forearm flexion (FLX) and extension (EXT) peak torque (PT) at 180°·s, height (HT), percent body fat (%BF), and fat-free mass (FFM) to the prediction of estimated propulsive force (EPF) and which of these variables should be a focus of training in young male swimmers. Thirty young male swimmers (mean age ± SD = 12.4 ± 2.7 years) volunteered for this study. The subjects were members of local swimming clubs who competed in the front crawl. The swimmers were measured for FLX and EXT PT at 180°·s, HT, body mass (BM), arm muscle area (AMA), arm circumference, triceps skinfold, %BF, and FFM. Arm muscle area was used to calculate EPF. Zero-order correlations and stepwise multiple regression analyses were used to examine the relationships among variables and the relative contributions of FLX, EXT, HT, %BF, and FFM to the prediction of EPF. Forearm flexion PT at 180°·s, EXT, BM, HT, FFM, AMA, and EPF were significantly intercorrelated (r = 0.83-1.00). In addition, 4 variables contributed significantly to the prediction of EPF (standardized regression coefficients = FFM [1.00], FLX [0.92], EXT [-0.62], and HT [-0.35]). Percent body fat did not contribute to any of the stepwise models. These findings suggested that age-related increases in HT and FFM, as well as training for increases in FLX and EXT strength may improve propulsive force and swimming performance in young male swimmers.

Topics: Adiposity; Adolescent; Body Height; Body Weight; Body Weights and Measures; Child; Forearm; Humans; Male; Muscle Strength; Muscle, Skeletal; Skinfold Thickness; Swimming; Torque

Juvenile idiopathic arthritis (JIA) is a chronic illness with a high risk of developing long-term disability. Disease activity is currently being monitored and quantified by ACR core set. Here, joint inflammation is determined; however joint function is the crucial component for developing disability. The aim of this study was to quantify and compare dynamic joint function in healthy and arthritic knee joints and to evaluate response to improvement.. A single center cohort study of consecutive children presenting to the rheumatology outpatient clinic was performed to measure dynamic knee joint function. Serial measures were performed if possible. Splint fixed electrogoniometers were used to measure dynamic knee joint function including ROM and flexion and extension torque.. A total of 54 children were tested including 44 with JIA, of whom eight had to be excluded for non-JIA-related knee problems. The study included 36 JIA patients of whom eight had strictly unilateral knee arthritis, and nine controls. Dynamic joint function ROM and torque depended on age and bodyweight, as demonstrated in healthy joints. ROM and torques were significant lower in arthritic compared to unaffected knee joints in children with unilateral arthritis and across the cohort. Importantly, extension torque was the most sensitive marker of impaired joint function. Follow up measurements detected responsiveness to change in disease activity.. Measuring dynamic joint function with electrogoniometers is feasible and objective. Active ROM and torque during flexion and extension of arthritic knee joints were significant lower compared to unaffected. In dynamic joint measurement extension torque is a sensitive marker for disease activity.

Topics: Adolescent; Age Factors; Arthritis, Juvenile; Arthrometry, Articular; Body Weight; Case-Control Studies; Child; Child, Preschool; Cohort Studies; Feasibility Studies; Female; Humans; Knee Joint; Male; Range of Motion, Articular; Severity of Illness Index; Torque; Young Adult

A prospective study was performed on the assessment of both thoracic and lumbar spine sagittal profiles (from C7 to S1).. To propose a new noninvasive method for measuring the spine curvatures in standing and lying prone positions and to analyze their relationship with various biometric characteristics.. Modifications of spine curvatures (i.e. lordosis or kyphosis) are of importance in the development of spinal disorders. Studies have emphasized the development of new devices to measure the spine sagittal profiles using a noninvasive and low-cost method. To date, it has not been applied for analyzing both lumbar and thoracic alterations for various positioning.. Seventy-five healthy subjects (mean 22.6 ± 4.3 yr) were recruited to participate in this study. Thoracic and lumbar sagittal profiles were assessed in standing and lying prone positions using a 3D digitizer. In addition, several biometric data were collected including maximal trunk isometric strength for flexion and extension movement. Statistical analysis consisted in data comparisons of spine profiles and a multivariate analysis including biometric features, to classify individuals considering low within- and high between-variability.. Kyphosis and lordosis angles decreased significantly from standing to lying prone position by an average of 13.4° and 16.6°, respectively. Multivariate analysis showed a sample clustering of 3 homogenous subgroups. The first group displayed larger lordosis and flexibility, and had low data values for height, weight, and strength. The second group had lower values than the overall trend of the whole sample, whereas the third group had larger score values for the torques, height, weight, waist, body mass index, and kyphosis angle but a reduced flexibility.. The present results demonstrate a significant effect of the positioning on both thoracic and lumbar spine sagittal profiles and highlight the use of cluster analysis to categorize subgroups after biometric characteristics including curvature measurement.. N/A.

Topics: Adolescent; Adult; Biometry; Body Height; Body Mass Index; Body Weight; Female; Healthy Volunteers; Humans; Imaging, Three-Dimensional; Isometric Contraction; Kyphosis; Lordosis; Lumbar Vertebrae; Male; Muscle Strength; Muscle, Skeletal; Prone Position; Prospective Studies; Range of Motion, Articular; Thoracic Vertebrae; Torque; Torso; Young Adult

The purpose of this study was to investigate the relationship between physiological, anthropometric, strength, and muscle power variables and a 5-km time trial (5kmT) in young runners. Twenty-three runners volunteered to participate in this study. Height, body mass, body fat, and fat-free mass (FFM) were measured. The subjects underwent laboratory testing to determine maximal oxygen uptake ((Equation is included in full-text article.)), velocity at ventilatory threshold (VVT), running economy (RE), velocity associated with maximal oxygen uptake ((Equation is included in full-text article.)), and peak velocity (PV). Peak torque, total work, and power were measured by an isokinetic dynamometer at 60°·s(-1) and 240°·s(-1) angular velocities. Right and left knee flexor and extensor torques were evaluated. Finally, the participants performed a 5kmT. Multiple regression and correlation analysis were used to determine the variables that significantly related to 5kmT. Strength and muscle power variables did not correlate with 5kmT. However, most physiological variables were associated with 5kmT. Velocity at ventilatory threshold alone explains 40% of the variance in 5kmT. The addition of the RE at speed 11.2 km·h(-1) (RE11.2) and FFM to the prediction equation allowed for 71% of the adjusted variance in 5kmT to be predicted. These results show that strength and muscle power variables are not good predictors of 5kmT; however, the physiological variables presented high prediction capacity in the 5kmT. Moreover, the anthropometric measures showed significant influence in performance prediction.

Topics: Adiposity; Adolescent; Athletic Performance; Body Height; Body Weight; Body Weights and Measures; Humans; Knee; Male; Muscle Strength; Muscle, Skeletal; Oxygen Consumption; Running; Torque; Young Adult

The medial collateral (MCL) and anterior cruciate ligaments (ACL) are, respectively, the primary and secondary ligamentous restraints against knee abduction, which is a component of the valgus collapse often associated with ACL rupture during athletic tasks. Despite this correlation in function, MCL ruptures occur concomitantly in only 20% to 40% of ACL injuries.. The purpose of this investigation was to determine how athletic tasks load the knee joint in a manner that could lead to ACL failure without concomitant MCL failure. It was hypothesized that (1) the ACL would provide greater overall contribution to intact knee forces than the MCL during simulated motion tasks and (2) the ACL would show greater relative peak strain compared with the MCL during simulated motion tasks.. Controlled laboratory study.. A 6-degrees-of-freedom robotic manipulator articulated 18 cadaveric knees through simulations of kinematics recorded from in vivo drop vertical jump and sidestep cutting tasks. Specimens were articulated in the intact-knee and isolated-ligament conditions. After simulation, each ACL and MCL was failed in uniaxial tension along its fiber orientations.. During a drop vertical jump simulation, the ACL experienced greater peak strain than the MCL (6.1% vs 0.4%; P < .01). The isolated ACL expressed greater peak anterior force (4.8% vs 0.3% body weight; P < .01), medial force (1.6% vs 0.4% body weight; P < .01), flexion torque (8.4 vs 0.4 N·m; P < .01), abduction torque (2.6 vs 0.3 N·m; P < .01), and adduction torque (0.5 vs 0.0 N·m; P = .03) than the isolated MCL. During failure testing, ACL specimens preferentially loaded in the anteromedial bundle failed at 637 N, while MCL failure occurred at 776 N.. During controlled physiologic athletic tasks, the ACL provides greater contributions to knee restraint than the MCL, which is generally unstrained and minimally loaded.. Current findings support that multiplanar loading during athletic tasks preferentially loads the ACL over the MCL, leaving the ACL more susceptible to injury. An enhanced understanding of joint loading during in vivo tasks may provide insight that enhances the efficacy of injury prevention protocols.

Topics: Anterior Cruciate Ligament; Anterior Cruciate Ligament Injuries; Biomechanical Phenomena; Body Weight; Cadaver; Exercise; Female; Humans; Knee Injuries; Knee Joint; Male; Medial Collateral Ligament, Knee; Middle Aged; Random Allocation; Range of Motion, Articular; Risk Factors; Robotics; Rupture; Sports; Sprains and Strains; Stress, Physiological; Torque

Learning to maintain standing balance in the presence of a paretic limb is an important recovery process for many stroke survivors. In this study, we used a robotic balance simulator to investigate whether manipulating medial-lateral or anterior-posterior torque contributions (i.e. input gains) could shift the control of balance toward a targeted lower limb in healthy controls. Manipulation of medial-lateral (ML) torque gains shifted the vertical load distribution toward the virtually weakened limb, but did not result in a significant shift in anterior-posterior (AP) torque control. Instead individual participants were observed to shift AP torque control in either direction, although participants more often shifted control toward the virtually weakened limb at larger ML asymmetries. In contrast, manipulation of AP torque gains did not produce any observable changes in measured torque signals. The shift in torque contributions during ML manipulations shows promise as an implicit training method for reducing weight-bearing asymmetry. However, further work is required to ensure both vertical load and AP torque control shift in the desired direction as well as to determine the applicability of the protocol in a patient population.

Topics: Adult; Body Weight; Computer Simulation; Extremities; Female; Humans; Male; Postural Balance; Posture; Robotics; Signal Processing, Computer-Assisted; Torque; Weight-Bearing

Differences in trunk strength capacity because of gender and sports are well documented in adults. In contrast, data concerning young athletes are sparse. The purpose of this study was to assess the maximum trunk strength of adolescent athletes and to investigate differences between genders and age groups. A total of 520 young athletes were recruited. Finally, 377 (n = 233/144 M/F; 13 ± 1 years; 1.62 ± 0.11 m height; 51 ± 12 kg mass; training: 4.5 ± 2.6 years; training sessions/week: 4.3 ± 3.0; various sports) young athletes were included in the final data analysis. Furthermore, 5 age groups were differentiated (age groups: 11, 12, 13, 14, and 15 years; n = 90, 150, 42, 43, and 52, respectively). Maximum strength of trunk flexors (Flex) and extensors (Ext) was assessed in all subjects during isokinetic concentric measurements (60°·s(-1); 5 repetitions; range of motion: 55°). Maximum strength was characterized by absolute peak torque (Flexabs, Extabs; N·m), peak torque normalized to body weight (Flexnorm, Extnorm; N·m·kg(-1) BW), and Flexabs/Extabs ratio (RKquot). Descriptive data analysis (mean ± SD) was completed, followed by analysis of variance (α = 0.05; post hoc test [Tukey-Kramer]). Mean maximum strength for all athletes was 97 ± 34 N·m in Flexabs and 140 ± 50 N·m in Extabs (Flexnorm = 1.9 ± 0.3 N·m·kg(-1) BW, Extnorm = 2.8 ± 0.6 N·m·kg(-1) BW). Males showed statistically significant higher absolute and normalized values compared with females (p < 0.001). Flexabs and Extabs rose with increasing age almost 2-fold for males and females (Flexabs, Extabs: p < 0.001). Flexnorm and Extnorm increased with age for males (p < 0.001), however, not for females (Flexnorm: p = 0.26; Extnorm: p = 0.20). RKquot (mean ± SD: 0.71 ± 0.16) did not reveal any differences regarding age (p = 0.87) or gender (p = 0.43). In adolescent athletes, maximum trunk strength must be discussed in a gender- and age-specific context. The Flexabs/Extabs ratio revealed extensor dominance, which seems to be independent of age and gender. The values assessed may serve as a basis to evaluate and discuss trunk strength in athletes.

Topics: Adolescent; Age Factors; Body Weight; Child; Female; Humans; Male; Muscle Strength; Muscle, Skeletal; Sex Factors; Torque; Torso

Age-associated loss of muscle mass (sarcopenia) and strength (dynapenia) is associated with a loss of independence that contributes to falls, fractures, and nursing home admissions, whereas regular physical activity has been suggested to offset these losses. The purpose of this study was to evaluate the effect of habitual endurance exercise on muscle mass and strength in active older adults. A longitudinal analysis of muscle strength (≈4.8 years apart) was performed on 59 men (age at start of study: 58.6 ± 7.3 years) and 35 women (56.9 ± 8.2 years) who used endurance running as their primary mode of exercise. There were no changes in fat-free mass although body fat increased minimally (1.0-1.5%). Training volume (km·wk, d·wk) decreased in both the men and women. There was a significant loss of both isometric knee extension (≈5% per year) and knee flexion (≈3.6% per year) strength in both the men and women. However, there was no significant change in either isokinetic concentric or eccentric torque of the knee extensors. Our data demonstrated a significant decline in isometric knee extensor and knee flexor strength although there were no changes in body mass in this group of very active older men and women. Our data support newer exercise guidelines for older Americans suggesting resistance training be an integral component of a fitness program and that running alone was not sufficient to prevent the loss in muscle strength (dynapenia) with aging.

Topics: Aged; Aged, 80 and over; Aging; Anaerobic Threshold; Body Composition; Body Weight; Female; Humans; Isometric Contraction; Knee; Leg; Longitudinal Studies; Male; Middle Aged; Muscle Strength; Muscle, Skeletal; Physical Endurance; Quadriceps Muscle; Running; Sarcopenia; Torque

The loads acting in knee joints must be known for improving joint replacement, surgical procedures, physiotherapy, biomechanical computer simulations, and to advise patients with osteoarthritis or fractures about what activities to avoid. Such data would also allow verification of test standards for knee implants. This work analyzes data from 8 subjects with instrumented knee implants, which allowed measuring the contact forces and moments acting in the joint. The implants were powered inductively and the loads transmitted at radio frequency. The time courses of forces and moments during walking, stair climbing, and 6 more activities were averaged for subjects with I) average body weight and average load levels and II) high body weight and high load levels. During all investigated activities except jogging, the high force levels reached 3,372-4,218N. During slow jogging, they were up to 5,165N. The peak torque around the implant stem during walking was 10.5 Nm, which was higher than during all other activities including jogging. The transverse forces and the moments varied greatly between the subjects, especially during non-cyclic activities. The high load levels measured were mostly above those defined in the wear test ISO 14243. The loads defined in the ISO test standard should be adapted to the levels reported here. The new data will allow realistic investigations and improvements of joint replacement, surgical procedures for tendon repair, treatment of fractures, and others. Computer models of the load conditions in the lower extremities will become more realistic if the new data is used as a gold standard. However, due to the extreme individual variations of some load components, even the reported average load profiles can most likely not explain every failure of an implant or a surgical procedure.

Topics: Activities of Daily Living; Aged; Arthroplasty, Replacement, Knee; Biomechanical Phenomena; Body Weight; Female; Humans; Jogging; Knee Joint; Knee Prosthesis; Male; Middle Aged; Osteoarthritis, Knee; Reference Standards; Reference Values; Stress, Mechanical; Torque; Walking

Material properties of tissue in vivo present an opportunity for clinical analysis of healing progression and pathologies as well as provide an excellent research tool yielding quantified data for longitudinal and cross population studies. Echogenicity is a material׳s ability to reflect sound and, using ultrasound, it has been shown to increase with tendon tension in vitro, though this non-invasive measurement technique for determining mechanical properties has not been tested in vivo. The aim of this study was to establish if echogenicity, seen by the increase in image brightness, could be correlated to stress within a tissue. 18 Achilles tendons were imaged in the sagittal and transverse planes while producing a series of isometric contractions starting from rest and producing the torque equivalent of 0.5, 1.0, 1.5, and 2.0× body weights. Manual tracing identified the tendon in each of the images. The cross-sectional area determined from the transverse plane images in conjunction with the tendon force yielded the tendon stress. The echogenicity of the tendon was determined from the mean brightness change from rest to each of the contraction cases, measured from the sagittal plane images. A weak correlation existed between the echogenicity and stress (R=0.25) but it was found that there was no significant change in axial area during contraction (p=0.683) establishing the tendon as incompressible. Echogenicity proved to be non-functional for measuring the mechanical properties of the Achilles tendon due to the additional factors included with in vivo testing e.g. tendon twist and multi-axial loading.

Topics: Achilles Tendon; Adult; Body Weight; Compressive Strength; Cross-Sectional Studies; Elasticity Imaging Techniques; Humans; Isometric Contraction; Stress, Mechanical; Tendons; Torque; Wound Healing; Young Adult

Neuromuscular electrical stimulation is well-known as a modality to improve the performance of neuromuscular system, but its clinical value on muscle strengthening remains equivocal. In this study, we designed a system for an involuntary eccentric contraction of biceps brachii muscles using continuous passive movement and commercial neuromuscular electrical stimulation devices.. To investigate the effects of involuntary eccentric contraction training by neuromuscular electrical stimulation on the enhancement of muscle strength, seven healthy men between the ages of 24 and 29 years participated in this study. Participants were trained two times per week for 12 weeks. Each exercise session was performed for 30 min with no rest intervals. Isometric elbow flexion torque and biceps brachii muscle thickness were chosen as evaluation indices, and were measured at pre-/post-training.. After the 12-week training, the isometric elbow flexion torque of the trained side significantly increased by approximately 23% compared to the initial performance (P<0.01). Meanwhile, the torque of the untrained side showed no significant change (P=0.862). During the 12-week training period, the biceps brachii muscle thickness of the trained side significantly increased by around 8% at rest and 16% at maximum voluntary contraction (P<0.01).. The developed system and the technique show promising results, suggesting that it has the potential to be used to increase the muscle strength in patients with neuromuscular disease and to be implemented in design rehabilitative protocols.

Topics: Adult; Arm; Body Weight; Elbow Joint; Electric Stimulation; Equipment Design; Exercise; Humans; Male; Muscle Contraction; Muscle Strength; Muscle, Skeletal; Rehabilitation; Retrospective Studies; Software; Torque; Ultrasonography

Robots are very useful tools in orthopedic research. They can provide force/torque controlled specimen motion with high repeatability and precision. A method to analyze dissipative energy outcome in an entire joint was developed in our group. In a previous study, a sheep knee was flexed while axial load remained constant during the measurement of dissipated energy. We intend to apply this method for the investigation of osteoarthritis. Additionally, the method should be improved by simulation of in vivo knee dynamics. Thus, a new biomechanical testing tool will be developed for analyzing in vitro joint properties after different treatments.. Discretization of passive knee flexion was used to construct a complex flexion movement by a robot and simulate altering axial load similar to in vivo sheep knee dynamics described in a previous experimental study.. The robot applied an in vivo like axial force profile with high reproducibility during the corresponding knee flexion (total standard deviation of 0.025 body weight (BW)). A total residual error between the in vivo and simulated axial force was 0.16 BW. Posterior-anterior and medio-lateral forces were detected by the robot as a backlash of joint structures. Their curve forms were similar to curve forms of corresponding in vivo measured forces, but in contrast to the axial force, they showed higher total standard deviation of 0.118 and 0.203 BW and higher total residual error of 0.79 and 0.21 BW for posterior-anterior and medio-lateral forces respectively.. We developed and evaluated an algorithm for the robotic simulation of complex in vivo joint dynamics using a joint specimen. This should be a new biomechanical testing tool for analyzing joint properties after different treatments.

Topics: Algorithms; Animals; Biomechanical Phenomena; Body Weight; Computer Simulation; Hindlimb; Joints; Movement; Osteoarthritis; Reproducibility of Results; Robotics; Sheep; Torque

The relationship between participation in highly competitive exercise, thigh muscle strength, and regional and total body bone mineral density (BMD) in elite senior athletes and healthy elderly controls was investigated. One hundred and four elite senior athletes (age: 72.6 ± 6.4 years, height: 168.7 ± 8.6 cm, mass: 72.6 ± 13.5 kg, 57 male:47 female) and 79 healthy controls (age: 75.4 ± 5.6 years, height: 170.8 ± 25.5 cm, mass: 79.5 ± 11.7 kg, 46 male:33 female) participated in this cross-sectional study. Vitamin D and calcium intake were assessed via a recall survey. Isometric knee extension and flexion peak torque were measured via a custom strength measurement device. Total body and regional BMD of the hip, radius, and spine were assessed with a dual-energy x-ray absorptiometer. For each BMD site assessed, multivariate linear regression analysis was performed in 4 steps (α = 0.10) to examine the contribution of (a) age, sex, bodyweight, and calcium and vitamin D intake; (b) group (elite senior athlete, control); (c) knee extension peak torque; and (d) knee flexion peak torque on BMD. Sex, age, bodyweight, and calcium and vitamin D intake explained a significant amount of variance in BMD in each site. Group was not significant. Knee extension peak torque explained an additional 3.8% of the variance in hip BMD (p = 0.06). Knee flexion peak torque was not correlated to BMD at any of the sites assessed. In conclusion, participation in highly competitive athletics was not related to total body or regional BMD. Age, sex, bodyweight, and vitamin D and calcium intake were significantly related to BMD at all the sites assessed. Quadriceps strength contributed slightly to hip BMD. Our results imply that participation in highly competitive senior athletics does not have a protective effect on BMD, perhaps because of a lower bodyweight or other confounding factors.

Topics: Age Factors; Aged; Aged, 80 and over; Body Weight; Bone Density; Calcium, Dietary; Competitive Behavior; Cross-Sectional Studies; Female; Hip; Humans; Isometric Contraction; Knee; Male; Muscle Strength; Quadriceps Muscle; Radius; Sex Factors; Spine; Sports; Torque; Vitamin D

It is not known whether the human anterior cruciate ligament (ACL) is susceptible to fatigue failure as a result of repetitive loading or whether certain knee morphologic characteristics increase that risk.. The number of knee loading cycles required to fail an ACL by fatigue failure is unaffected by the magnitude of the external load delivered to the knee joint. Furthermore, sex, ACL cross-sectional area, and lateral tibial slope will not affect the number of loading cycles to ACL failure.. Controlled laboratory study.. Knee pairs from 10 cadaveric donors (5 female) of similar age, height, and weight were imaged with 3-T magnetic resonance imaging to measure lateral tibial slope and ACL cross-sectional area. One knee from each pair was then subjected to repeated application of a load of 3 times body weight (3*BW), while the other knee was subjected to a 4*BW load, both involving impulsive compression force, knee flexion moment, and internal tibial torque combined with realistic trans-knee muscle forces. The resulting 3-dimensional tibiofemoral kinematics and kinetics were recorded, along with ACL relative strain and quadriceps, hamstring, and gastrocnemius muscle forces. The loading cycle was repeated until the ACL ruptured, a 3-mm increase in cumulative anterior tibial translation occurred, or a minimum of 50 trials was reached.. Eight of 10 knees failed under the 4*BW load (mean ± SD cycles to failure, 21 ± 18), while 5 of 10 knees failed under the 3*BW load (mean ± SD cycles to failure, 52 ± 10). Four knees exhibited a 3-mm increase in anterior tibial translation, 7 knees developed partial or complete visible ACL tears, and 2 knees developed complete ACL tibial avulsions. A Cox regression showed that the number of cycles to ACL failure was influenced by the simulated landing force (P = .012) and ACL cross-sectional area (P = .022). Donor sex and lateral tibial slope did not influence the number of cycles to ACL failure.. The human ACL is susceptible to fatigue failure when pivot landings of 3*BW or more load the knee repeatedly within a short time span. An ACL with a smaller cross-sectional area is at greater risk for this type of failure.. The results show that the human knee can only withstand a certain number of 3*BW or greater jump loading cycles within a short time period before the ACL will fail. Therefore, limiting the increase in the number and severity of pivot landing maneuvers performed over a week of training would make sense from an injury prevention viewpoint.

Topics: Anterior Cruciate Ligament; Anterior Cruciate Ligament Injuries; Body Weight; Cadaver; Compressive Strength; Fatigue; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Movement; Proportional Hazards Models; Stress, Mechanical; Stress, Physiological; Torque

The purpose of this investigation was to assess the effects of stance width and foot rotation angle on three-dimensional knee joint moments during bodyweight squat performance. Twenty-eight participants performed 8 repetitions in 4 conditions differing in stance or foot rotation positions. Knee joint moment waveforms were subjected to principal component analysis. Results indicated that increasing stance width resulted in a larger knee flexion moment magnitude, as well as larger and phase-shifted adduction moment waveforms. The knee's internal rotation moment magnitude was significantly reduced with external foot rotation only under the wide stance condition. Moreover, squat performance with a wide stance and externally rotated feet resulted in a flattening of the internal rotation moment waveform during the middle portion of the movement. However, it is speculated that the differences observed across conditions are not of clinical relevance for young, healthy participants.

Topics: Body Weight; Computer Simulation; Foot; Humans; Knee Joint; Models, Biological; Movement; Muscle Contraction; Muscle, Skeletal; Posture; Rotation; Task Performance and Analysis; Torque; Young Adult

Existing models of muscle deconditioning such as bed rest are expensive and time-consuming. We propose a new model utilizing a weighted suit to manipulate muscle strength, power, or endurance relative to body weight. The aims of the study were to determine as to which muscle measures best predict functional task performance and to determine muscle performance thresholds below which task performance is impaired. Twenty subjects performed seven occupational astronaut tasks (supine and upright seat egress and walk, rise from fall, hatch opening, ladder climb, object carry, and construction board activity), while wearing a suit weighted with 0-120 % of body weight. Models of the relationship between muscle function/body weight and task completion time were developed using fractional polynomial regression and verified with pre- and post-flight astronaut performance data. Spline regression was used to identify muscle function thresholds for each task. Upright seat egress and walk was the most difficult task according to the spline regression analysis thresholds. Thresholds normalized to body weight were 17.8 N/kg for leg press isometric force, 17.6 W/kg for leg press power, 78.8 J/kg for leg press work, 5.9 N/kg isometric knee extension and 1.9 Nm/kg isokinetic knee extension torque. Leg press maximal isometric force/body weight was the most reliable measure for modeling performance of ambulatory tasks. Laboratory-based manipulation of relative strength has promise as an analog for spaceflight-induced loss of muscle function. Muscle performance values normalized to body weight can be used to predict occupational task performance and to establish relevant strength thresholds.

Topics: Activities of Daily Living; Adult; Biomechanical Phenomena; Body Weight; Equipment Design; Female; Humans; Isometric Contraction; Male; Middle Aged; Motor Activity; Muscle Strength; Muscle, Skeletal; Regression Analysis; Space Flight; Space Suits; Supine Position; Task Performance and Analysis; Time Factors; Torque; Walking

The purpose of this study was to investigate ground reaction forces (GRF) in collegiate baseball pitchers and their relationship to pitching mechanics. Fourteen healthy collegiate baseball pitchers participated in this study. High-speed video and force plate data were collected for fastballs from each pitcher. The average ball speed was 35 ± 3 m/sec (78 ± 7 mph). Peak GRFs of 245 ± 20% body weight (BW) were generated in an anterior or braking direction to control descent. Horizontal GRFs tended to occur in a laterally directed fashion, reaching a peak of 45 ± 63% BW. The maximum vertical GRF averaged 202 ± 43% BW approximately 45 milliseconds after stride foot contact. A correlation between braking force and ball velocity was evident. Because of the downward inclination and rotation of the pitching motion, in addition to volume, shear forces may occur in the musculoskeletal tissues of the stride limb leading to many of the lower-extremity injuries seen in this athletic population.

Topics: Adult; Baseball; Biomechanical Phenomena; Body Weight; Elbow; Humans; Lower Extremity; Rotation; Shoulder; Torque; Videotape Recording; Weight-Bearing; Young Adult

Football turf is increasingly used in European soccer competition. Little is known on the rotational torque that players experience on these fields. High rotational torques between the shoe outsole and the sports surface has been correlated with torsional injuries of the lower limb and knee.. To evaluate the effect of six parameters that could influence the rotational torque between the shoe outsole and the latest generation football turf.. Controlled laboratory study.. A testing apparatus was constructed to measure the peak torque generated during a controlled rotation of the foot. Six parameters that could potentially influence the frictional forces, were considered: (1) the sports surface, (2) the shoe outsole cleat design, (3) the weather conditions, (4) the weight, (5) the presence of an impact and (6) the direction of rotation.. The football turf without infill showed significantly lower frictional torques than natural grass whereas a football turf with sand/rubber infill had significantly higher torques. Blades were associated with significantly higher torques than studs on natural grass and on one football turf with sand/rubber infill. Dry weather was associated with higher torques only for the football turf without infill. The torque increased linearly and significantly with an increasing vertical load. The rotational torque increased significantly following an impact. Torques on external rotational movements were significantly higher with blades.. Important differences in rotational torques are found and could be seen as potential risk factors for torsional injuries of the lower limb.

Topics: Body Weight; Equipment Design; Female; Floors and Floorcoverings; Friction; Humans; Leg Injuries; Male; Shoes; Soccer; Sports Equipment; Torque; Torsion Abnormality

This paper describes the application of a powered lower limb exoskeleton to aid paraplegic individuals in stair ascent and descent. A brief description of the exoskeleton hardware is provided along with an explanation of the control methodology implemented to allow stair ascent and descent. Tests were performed with a paraplegic individual (T10 complete injury level) and data is presented from multiple trials, including the hip and knee joint torque and power required to perform this functionality. Joint torque and power requirements are summarized, including peak hip and knee joint torque requirements of 0.75 Nm/kg and 0.87 Nm/kg, respectively, and peak hip and knee joint power requirements of approximately 0.65 W/kg and 0.85 W/kg, respectively.

Topics: Body Weight; Evaluation Studies as Topic; Humans; Lower Extremity; Male; Orthotic Devices; Paraplegia; Posture; Torque; Walking

Optimal performance of a dynamical pole vault process was modeled as a constrained nonlinear optimization problem. That is, given a vaulter's anthropomorphic data and approach speed, the vaulter chose a specific take-off angle, pole stiffness and gripping height in order to yield the greatest jumping height compromised by feasible bar-crossing velocities. The optimization problem was solved by nesting a technique of searching an input-to-output mapping arising from the vaulting trajectory and a method of nonlinear sequential quadratic programming (SQP). It was suggested from the optimization results that the body's weight has an important influence on the vaulting performance beside the vaulter's height and approach speed; the less skilled vaulter should gradually adopt a longer pole to improve the performance.

Topics: Athletic Performance; Biomechanical Phenomena; Body Weight; Computer Simulation; Humans; Torque; Track and Field

Since cut-out still remains one of the major clinical challenges in the field of osteoporotic proximal femur fractures, remarkable developments have been made in improving treatment concepts. However, the mechanics of these complications have not been fully understood.We hypothesize using the experimental data and a theoretical model that a previous rotation of the femoral head due to de-central implant positioning can initiate a cut-out.. In this investigation we analysed our experimental data using two common screws (DHS/Gamma 3) and helical blades (PFN A/TFN) for the fixation of femur fractures in a simple theoretical model applying typical gait pattern on de-central positioned implants. In previous tests during a forced implant rotation by a biomechanical testing machine in a human femoral head the two screws showed failure symptoms (2-6Nm) at the same magnitude as torques acting in the hip during daily activities with de-central implant positioning, while the helical blades showed a better stability (10-20Nm).To calculate the torque of the head around the implant only the force and the leverarm is needed (N [Nm] = F [N] * × [m]). The force F is a product of the mass M [kg] multiplied by the acceleration g [m/s2]. The leverarm is the distance between the center of the head of femur and the implant center on a horizontal line.. Using 50% of 75 kg body weight a torque of 0.37Nm for the 1 mm decentralized position and 1.1Nm for the 3 mm decentralized position of the implant was calculated. At 250% BW, appropriate to a normal step, torques of 1.8Nm (1 mm) and 5.5Nm (3 mm) have been calculated.Comparing of the experimental and theoretical results shows that both screws fail in the same magnitude as torques occur in a more than 3 mm de-central positioned implant.. We conclude the center-center position in the head of femur of any kind of lag screw or blade is to be achieved to minimize rotation of the femoral head and to prevent further mechanical complications.

Topics: Aged, 80 and over; Biomechanical Phenomena; Body Weight; Bone Screws; Cadaver; Equipment Failure Analysis; Femur Head; Fracture Fixation, Internal; Hip Fractures; Humans; Male; Materials Testing; Models, Theoretical; Prosthesis Design; Prosthesis Failure; Range of Motion, Articular; Rotation; Torque; Weight-Bearing

The purpose of this study was to demonstrate the feasibility of producing an orthotic knee joint that could lock and unlock during ambulation for eventual use in a reciprocating gait orthosis (RGO) for severely disabled patients.. Three prototype orthotic knee joints incorporating braking mechanisms were designed and manufactured to demonstrate their ability to withstand a maximum calculated sagittal plane bending moment of 73 Nm. Each was then subjected to bench trials to test their performance against the required specification.. Although all three joints achieved the requirement to sustain the specified externally applied bending moments, the hydraulic disc brake system proved significantly superior and was selected for more comprehensive testing.. The results confirmed the feasibility of utilising a hydraulic braking mechanism within an orthotic knee joint to withstand the knee flexing moments during walking in a lower limb orthosis. This gave the development group confidence to progress to the prototype design phase with the specific aim of eventually incorporating such a joint in an RGO designed for severely disabled patients such as those with complete paraplegia up to level T4 and those with severe neurological dysfunction.

Topics: Body Weight; Braces; Gait; Gait Disorders, Neurologic; Humans; Knee Joint; Pilot Projects; Torque

Robotic locomotor training devices have gained popularity in recent years, yet little has been reported regarding contact forces experienced by the subject performing automated locomotor training, particularly in animal models of neurological injury. The purpose of this study was to develop a means for acquiring contact forces between a robotic device and a rodent model of spinal cord injury through instrumentation of a robotic gait training device (the rat stepper) with miniature force/torque sensors. Sensors were placed at each interface between the robot arm and animal's hindlimb and underneath the stepping surface of both hindpaws (four sensors total). Twenty four female, Sprague-Dawley rats received mid-thoracic spinal cord transections as neonates and were included in the study. Of these 24 animals, training began for 18 animals at 21 days of age and continued for four weeks at five min/day, five days/week. The remaining six animals were untrained. Animal-robot contact forces were acquired for trained animals weekly and untrained animals every two weeks while stepping in the robotic device with both 60 and 90% of their body weight supported (BWS). Animals that received training significantly increased the number of weight supported steps over the four week training period. Analysis of raw contact forces revealed significant increases in forward swing and ground reaction forces during this time, and multiple aspects of animal-robot contact forces were significantly correlated with weight bearing stepping. However, when contact forces were normalized to animal body weight, these increasing trends were no longer present. Comparison of trained and untrained animals revealed significant differences in normalized ground reaction forces (both horizontal and vertical) and normalized forward swing force. Finally, both forward swing and ground reaction forces were significantly reduced at 90% BWS when compared to the 60% condition. These results suggest that measurement of animal-robot contact forces using the instrumented rat stepper can provide a sensitive and reliable measure of hindlimb locomotor strength and control of flexor and extensor muscle activity in neurologically impaired animals. Additionally, these measures may be useful as a means to quantify training intensity or dose-related functional outcomes of automated training.

Topics: Animals; Biomechanical Phenomena; Body Weight; Female; Hindlimb; Locomotion; Mechanical Phenomena; Physical Conditioning, Animal; Rats; Rats, Sprague-Dawley; Robotics; Spinal Cord Injuries; Torque

Studies that have attempted to address the influence of exercise programs on muscle strength have usually analyzed single exercise training types. They have not often addressed multicomponent exercise interventions that combine strength, flexibility, balance and aerobic training. The aim of the present study was to assess and compare improvements in muscle strength induced by 24 weeks of two training regimens in elderly adults aged 65-82 years.. Participants underwent a multicomponent exercise program (ME, n=25, 69.4+/-4.1 yrs) or combined ME plus resistance training (CE, n=24, 68.7+/-4.2 yrs). Maximum strength of knee extensors (KE) and flexors (KF) was measured at 60 masculine/s and 180 masculine/s with an isokinetic dynamometer before and 12 and 24 weeks after the training programs.. The CE group showed a significant increase in maximum voluntary knee extensors (22.3%, p<0.001) and knee flexors (29.6%, p<0.001) at 180 masculine/s in the non-dominant leg, in knee extensor torque at 60 masculine/s in the dominant (6.7%, p=0.023) and non-dominant leg (17.3%, p<0.001) and in knee flexor torque at 60 masculine/s in dominant (16.4%, p=0.020) and non-dominant leg (24.2%, p<0.001). No significant changes were observed in the ME group after 24 weeks of training.. The present study indicates that twice-weekly ME has a limited effect on isokinetic muscle strength. Our results also emphasize that adding moderate intensity resistance exercise twice a week to a ME protocol is sufficient to induce higher and significant strength improvements in healthy older subjects.

Topics: Aged; Aged, 80 and over; Body Height; Body Weight; Dominance, Cerebral; Exercise; Humans; Knee Joint; Muscle Strength; Resistance Training; Torque; Weight Lifting

This study investigated the event-related differences in the cross-sectional areas (CSAs) and torque generation capabilities of the quadriceps femoris (QF) and hamstrings (HAM) in male high school athletes. Subjects were soccer players (n=32), volleyball players (21), rowers (29), karate athletes (18), sumo wrestlers (15), sprinters (22), throwers (16), and nonathletes (20). The CSAs of QF and HAM at the mid-thigh were determined using magnetic resonance imaging. In addition, isokinetic torques during knee extension and flexion were determined at a pre-set velocity of 1.05 rad/s. The CSAs of the two muscle groups and torques developed in the two motions were significantly related to the two-third power of lean body mass (LBM(2/3)) and the product of CSA and femur length (CSA*fl), calculated as an index of muscle volume, respectively. CSA relative to LBM(2/3) for QF did not differ among the groups, but that for HAM was higher in sprinters, soccer players, throwers, and karate athletes than in sumo wrestlers, rowers, volleyball players, and nonathletes. Knee extension torque relative to the CSA*fl of QF was higher in karate athletes, soccer players, and rowers than in nonathletes, but the corresponding value for knee flexion did not differ among groups. Thus, the present study indicated that, at least in male high school athletes, the event-related differences in LBM and the muscularity of QF and HAM produced the corresponding differences in the CSAs of the reciprocal muscle groups and knee extension and flexion torques, respectively. However, specific profiles related to competitive and/or training styles exist in HAM CSA and knee extension torque, which cannot be explained by the magnitude of LBM and QF CSA, respectively.

Topics: Adolescent; Analysis of Variance; Anatomy, Cross-Sectional; Athletes; Biomechanical Phenomena; Body Weight; Humans; Magnetic Resonance Imaging; Male; Quadriceps Muscle; Torque

A number of devices have been developed to measure joint stiffness. This study investigated the reliability of the Intelligent (Intel) stretch device to measure bilateral ankle joint stiffness during passive range of motion (ROM).. The reliability of the device was investigated based on torque and angle by establishing the consistency of measurements between examiners on different testing days. In addition, demographic variables were analyzed to investigate the degree of stiffness. Forty-six gender-matched subjects completed the test.. The reliability ICC₂(,)₁ coefficient of ankle stiffness between-day for both examiners was 0.77 for the right ankle and 0.76 for the left ankle with a 0.05 standard error of measurement (SEM) for ankle stiffness for the right side and 0.04 for the left side. The ICC values of the two examiners were also high based on Chronbach's alpha (0.87 and 0.86). Among the demographic variables, gender (F=35.25, p=0.001) and body weight (F=23.55, p=0.001) were the most important factors in determining ankle joint stiffness.. The results of this study indicated that dorsiflexion and plantarflexion measurements obtained by the Intel stretch device are reproducible and consistent. In addition, ankle stiffness was significantly different based on gender and body weight to develop and/or maintain ankle function. These results may help to identify ankle stiffness factors that will lead to more efficient rehabilitation programs and injury prevention strategies.

Topics: Adult; Ankle Joint; Body Weight; Decision Making, Computer-Assisted; Electromyography; Feedback; Female; Humans; Male; Middle Aged; Physical Therapy Modalities; Range of Motion, Articular; Regression Analysis; Reproducibility of Results; Sex Factors; Torque

To examine whether normalized quadriceps and hamstring strength would predict quadriceps and hamstring muscle activation amplitudes and whether these neuromuscular factors would predict knee kinematics and kinetics during a drop jump task.. Thirty-nine females and 39 males were measured for isometric quadriceps and hamstring strength and were instrumented to obtain surface electromyography, kinematic, and kinetic measures during the initial landing of a drop jump. Multiple linear regressions first examined the relationship between thigh strength and activation then examined whether these neuromuscular variables were predictive of hip and knee flexion excursions, knee extensor moments (KEM), and anterior knee shear forces during the deceleration phase of the drop jump.. Females versus males produced lower normalized thigh strength and demonstrated greater quadriceps and hamstring activation amplitudes during the drop jump. Lower thigh muscle strength was a weak (males) to moderate (females) predictor of greater quadriceps activation amplitudes. However, thigh strength and activation were poor predictors of hip and knee joint excursions and KEM. Regardless of sex and thigh strength, anterior shear forces were greater in individuals who demonstrated less hip flexion and greater knee flexion excursions and greater peak quadriceps activation and internal KEM during the landing.. Although thigh muscle strength explained some of the variance in quadriceps and hamstring activation levels as measured with surface electromyography, we failed to support the hypothesis that these neuromuscular factors are strong predictors of sagittal plane hip and knee flexion excursions or KEM. Although greater quadriceps activation amplitude was a significant predictor of greater anterior tibial shear forces, its contribution was relatively small compared with kinematic and kinetic variables.

Topics: Anterior Cruciate Ligament Injuries; Biomechanical Phenomena; Body Weight; Exercise Test; Female; Humans; Knee; Male; Movement; Muscle Strength; Risk Factors; Thigh; Torque; Weight-Bearing; Young Adult

Forward dynamics simulations of a dismount preparation swing on the uneven parallel bars were optimized to investigate the sensitivity of dismount revolution potential to the maximum bar force before slipping, and to low-bar avoidance. All optimization constraints were classified as 1-anatomical/physiological; limiting maximum hand force on the high bar before slipping, joint ranges of motion and maximum torques, muscle activation/deactivation timing and 2-geometric; avoiding low-bar contact, and requiring minimum landing distance. The gymnast model included torso/head, arm and two leg segments connected by a planar rotating, compliant shoulder and frictionless ball-and-socket hip joints. Maximum shoulder and hip torques were measured as functions of joint angle and angular velocity. Motions were driven by scaling maximum torques by a joint torque activation function of time which approximated the average activation of all muscles crossing the joint causing extension/flexion, or adduction/abduction. Ten joint torque activation values, and bar release times were optimized to maximize dismount revolutions using the downhill simplex method. Low-bar avoidance and maximum bar-force constraints are necessary because they reduce dismount revolution potential. Compared with the no low-bar performance, optimally avoiding the low bar by piking and straddling (abducting) the hips reduces dismount revolutions by 1.8%. Using previously reported experimentally measured peak uneven bar-force values of 3.6 and 4.0 body weight (BW) as optimization constraints, 1.40 and 1.55 revolutions with the body extended and arms overhead were possible, respectively. The bar-force constraint is not active if larger than 6.9 BW, and instead performances are limited only by maximum shoulder and hip torques. Bar forces accelerate the mass center (CM) when performing muscular work to flex/extend the joints, and increase gymnast mechanical energy. Therefore, the bar-force constraint inherently limits performance by limiting the ability to do work and reducing system energy at bar release.

Topics: Athletes; Biomechanical Phenomena; Body Weight; Computational Biology; Computer Simulation; Female; Gymnastics; Humans; Joints; Models, Statistical; Motion; Movement; Muscles; Shoulder; Torque

Normal human locomotion requires the ability to control a complex, redundant neuromechanical system to repetitively cycle the legs in a stable manner. In a reduced paradigm of locomotion, hopping, we investigated the ability of human subjects to exploit motor redundancy in the legs to coordinate joint torques fluctuations to minimize force fluctuations generated against the ground. Although we saw invariant performance in terms of force stabilization across frequencies, we found that the role of joint torque coordination in stabilizing force was most important at slow hopping frequencies. Notably, the role of this coordinated variation strategy decreased as hopping frequency increased, giving way to an independent joint variation strategy. At high frequencies, the control strategy to stabilize force was more dependent on a direct reduction in ankle torque fluctuations. Through the systematic study of how joint-level variances affect task-level end-point function, we can gain insight into the underlying control strategies in place for automatically counteracting cycle-to-cycle deviations during normal human locomotion.

Topics: Adult; Analysis of Variance; Biomechanical Phenomena; Body Height; Body Weight; Female; Functional Laterality; Humans; Joints; Locomotion; Male; Motor Activity; Psychomotor Performance; Torque; Walking; Young Adult

The activation capacities and neuromuscular efficiency (NME) of the triceps surae (TS) of prepubescent children (7-11 years) and adults were evaluated during submaximal and maximal (MVC) isometric plantarflexion to determine whether they varied with age. TS-EMG were obtained by summing-up the rectified electromyograms of the soleus and gastrocnemii muscles; these data were quantified using a sliding average method and normalized with reference to the TS maximal compound action potential (TS-M-wave). The maximal EMG increased significantly with age in the children, but less than MVC, what led to a significant increase in NME(Max) (MVC/TS-EMG(max) ratio). The EMG-torque relationship indicated an age-related overactivation of TS at low torque, what led to a lower NME(Sub-max) (inverse of the slope of the EMG-torque relationship) for the youngest children. The overactivation of TS was accompanied by contraction of the TA, which decreased with age. The youngest children were also less able to maintain a target torque and muscle activation. Finally, the twitch interpolated method revealed an age-dependant activation deficit. We conclude that central mechanisms are the main cause of the lower torques developed by children and they appear to vary with age in prepubertal children.

Topics: Action Potentials; Adult; Age Factors; Ankle Joint; Body Height; Body Weight; Child; Electric Stimulation; Electromyography; Ergometry; Female; Humans; Isometric Contraction; Knee Joint; Male; Muscle Contraction; Muscle, Skeletal; Puberty; Reference Values; Torque

The posttraumatic response to a severe burn leads to marked and prolonged skeletal muscle catabolism and weakness, which persist despite standard rehabilitation programs of occupational and physical therapy. We investigated the degree to which the prolonged skeletal muscle catabolism affects the muscle function of children 6 months after severe burn.. Burned children, with >40% total body surface area burned, were assessed at 6 months after burn in respect to lean body mass and leg muscle strength at 150 degrees /s. Lean body mass was assessed using dual-energy X-ray absorptiometry. Leg muscle strength was assessed using isokinetic dynamometry. Nonburned children were assessed similarly, and served as controls.. We found that severely burned children (n=33), relative to nonburned children (n=46) had significantly lower lean body mass. Additionally they had significantly lower peak torque as well total work performance using the extensors of the thigh.. Our results serve as an objective and a practical clinical approach for assessing muscle function and also aid in establishing potential rehabilitation goals, and monitoring progress towards these goals in burned children.

Topics: Absorptiometry, Photon; Adolescent; Analysis of Variance; Body Mass Index; Body Weight; Burns; Case-Control Studies; Child; Energy Metabolism; Female; Humans; Male; Muscle Proteins; Muscle Strength; Muscle, Skeletal; Torque

The purposes of the study were to establish isometric torque reference values for healthy 6- to 8-year-old children for 6 lower extremity muscles and determine the effects of gender, age, height, weight, and physical activity upon strength.. A hand-held dynamometer was used to obtain force/torque values for 154 children.. Age-referenced force/torque and cutoff values are provided for each muscle group. Torque increased with age and height for all muscles and with weight for all muscles except knee extensors. No gender differences were found. Children who participated in 3 or more hours per week in organized sports were stronger in 4 of 6 muscles; the number of hours spent in active play did not affect torque.. This study provides hand-held dynamometer strength reference values to enable clinicians to determine if clients of the same age, height, and weight have muscle weakness.

Topics: Body Height; Body Weight; Child; Female; Humans; Isometric Contraction; Male; Motor Activity; Muscle Strength; Muscle Strength Dynamometer; Pilot Projects; Reference Values; Reproducibility of Results; Torque

To examine the reliability of clinical techniques for testing hip abductor and adductor muscle performance.. Repeated measures.. Academic laboratory.. A sample of 21 healthy subjects (12 men, 9 women) between 22 and 31 years of age.. Not applicable.. Reliability of repeated measures was estimated by calculating intraclass correlation coefficients. Torque production capability was calculated by multiplying force output obtained with a hand-held dynamometer by the length of the resistance lever arm.. The reliability of abduction testing was greatest in the long-lever condition. Adduction test reliability was greatest in the long-lever condition with bench stabilization. The maximal hip abduction torque tested in the long-lever position was significantly greater (t(20)=9.21, P<.001) than that in the short-lever position. The maximal hip adduction torque occurred using a long lever for resistance application and a bench to stabilize the nontest leg (F(1,20)=15.64, P=.001).. Muscle performance testing of hip abductors and adductors with a hand-held dynamometer can be performed with good to excellent intratester and intertester reliability. Hip abduction testing is best performed with a long lever. Hip adduction is best performed with a long lever and a bench to stabilize the nontest extremity.

Topics: Adult; Analysis of Variance; Body Height; Body Mass Index; Body Weight; Equipment Design; Female; Hip; Humans; Male; Minnesota; Muscle Contraction; Muscle Strength Dynamometer; Muscle Weakness; Observer Variation; Physical Examination; Pronation; Sensitivity and Specificity; Single-Blind Method; Supination; Torque

Dynamometric studies of grip strength are widely used in clinics. We present a clinic dynamometer that can be used to measure pronation and supination moments while the subject being tested is holding a cylindrical handle in neutral pronosupination. One hundred volunteers without any previous history of upper extremity injury were tested in pronation and supination in order to provide a database of strength values and to study variations with respect to sex, age, dominance, weight and height.

Topics: Adult; Age Factors; Body Height; Body Weight; Data Interpretation, Statistical; Female; Hand Strength; Humans; Male; Muscle Strength Dynamometer; Outpatients; Prone Position; Sex Factors; Supine Position; Torque; Wrist

Variations in joint parameter (JP) values (axis positions and orientations in body segments) and inertial parameter (IP) values (segment masses, mass centers, and moments of inertia) as well as kinematic noise alter the results of inverse dynamics analyses of gait. Three-dimensional linkage models with joint constraints have been proposed as one way to minimize the effects of noisy kinematic data. Such models can also be used to perform gait optimizations to predict post-treatment function given pre-treatment gait data. This study evaluates whether accurate patient-specific JP and IP values are needed in three-dimensional linkage models to produce accurate inverse dynamics results for gait. The study was performed in two stages. First, we used optimization analyses to evaluate whether patient-specific JP and IP values can be calibrated accurately from noisy kinematic data, and second, we used Monte Carlo analyses to evaluate how errors in JP and IP values affect inverse dynamics calculations. Both stages were performed using a dynamic, 27 degrees-of-freedom, full-body linkage model and synthetic (i.e., computer generated) gait data corresponding to a nominal experimental gait motion. In general, JP but not IP values could be found accurately from noisy kinematic data. Root-mean-square (RMS) errors were 3 degrees and 4 mm for JP values and 1 kg, 22 mm, and 74 500 kg * mm2 for IP values. Furthermore, errors in JP but not IP values had a significant effect on calculated lower-extremity inverse dynamics joint torques. The worst RMS torque error averaged 4% bodyweight * height (BW * H) due to JP variations but less than 0.25% (BW * H) due to IP variations. These results suggest that inverse dynamics analyses of gait utilizing linkage models with joint constraints should calibrate the model's JP values to obtain accurate joint torques.

Topics: Biomechanical Phenomena; Body Height; Body Weight; Calibration; Computer Simulation; Gait; Humans; Joints; Kinetics; Lower Extremity; Male; Models, Biological; Monte Carlo Method; Musculoskeletal System; Torque

The purpose of the present investigation was to examine the effects of a collegiate wrestling season on body weight, hydration, and muscular performance. Twelve Division I collegiate wrestlers (mean +/- SE; 20.75 +/- 0.41 year) volunteered to participate in testing sessions during midseason and 3 weeks following the season. Testing consisted of weigh-in, providing a urine sample for hydration analysis, and a measure of isometric leg extension peak torque. Weight significantly increased (p < 0.05) following the completion of the competitive season. No significant change in urine specific gravity (p > 0.05) was observed. Muscular performance was affected by the season as peak torque (PT) and PT-to-body weight ratio increased significantly (p < 0.05). Following the collegiate wrestling season, augmentation in body weight and muscular performance of the wrestlers occurs without alterations in hydration status. Further research is warranted on what type of strength training program would most effectively reduce the decrements in strength associated with weight loss and the strain of a competitive season.

Topics: Adult; Body Weight; Humans; Isometric Contraction; Leg; Male; Muscle Strength; Seasons; Specific Gravity; Students; Torque; Universities; Urinalysis; Water-Electrolyte Balance; Wrestling

Nitric oxide (NO) is a signaling molecule synthesized from l-arginine by nitric oxide synthases (NOSs). NOS isoforms are either constitutive (endothelial NOS [eNOS] and neuronal NOS [nNOS]) or inducible NOS (iNOS). Previously, our group has reported that NO is expressed during and modulates fracture healing. In this study, we evaluated the specific contribution of iNOS to fracture healing by using iNOS gene therapy in iNOS-deficient mice. Twelve-week-old female wild-type mice and iNOS-KO mice had a right femoral midshaft osteotomy fixed with an intramedullary 0.5-mm-diameter needle. A gelatine sponge was implanted across the fracture site. The gelatine sponge received either Ad5-CMViNOS (in iNOS-deficient mice; n=16) or Ad5-CMVempty (in wild-type mice; n=15, and iNOS-deficient mice; n=15) at a dose of 10(7) pfu. Mice were sacrificed at day 14, and their right and left hind limbs were harvested. Cross-sectional area (CSA) was determined by measuring the callus diameter across the mediolateral and anteroposterior plane using a vernier caliper. Specimens were loaded to failure torsionally in a biaxial INSTRON testing system, and maximum torque, torsional stiffness, and maximal and total energy were determined. Deletion of the iNOS gene decreased the total and maximum energy absorption of the healing femoral fracture by 30% and by 70% (P<0.01), respectively, in comparison to the wild-type mice. This reduction in energy absorption was reversed by iNOScDNA administration via adenovirus vector. Furthermore, iNOScDNA caused an increase in torsional failure by 20% (P=0.01) in comparison to iNOS(-/-) mice that did not receive the iNOScDNA. There were no significant differences in the biomechanical properties of intact femora. These data indicate that iNOS is important in mouse fracture healing. However, the clinical utility of NOS gene therapy to enhance fracture healing will need further evaluation.

Topics: Animals; Biomechanical Phenomena; Body Weight; Bony Callus; Female; Femur; Fracture Healing; Gene Deletion; Genetic Therapy; Mice; Mice, Knockout; Nitric Oxide Synthase Type II; Osteotomy; Torque

To determine and compare lower-limb force production during a single-leg horizontal press in involved and uninvolved limbs in people with unilateral total knee arthroplasty (TKA) and the limb of age- and gender-matched subjects.. Quasi-experimental, posttest only control group design.. Subjects living in the community and were tested at a university facility.. Nine people with unilateral TKA and 9 subjects without TKA volunteered. The mean postsurgery time for the TKA group was 15.89+/-6.62 months.. Not applicable.. Force production in kilograms during a single-leg press.. Lower-limb force production differed significantly between involved and uninvolved limbs (P=.007) for the unilateral TKA group. Lower-limb force production of the involved limb in persons with unilateral TKA was significantly lower than the limb of the age- and gender-matched controls (P=.0001).. Lower-limb force production on the involved side was significantly lower than the uninvolved side. When compared with an age-matched control group, subjects with unilateral TKA produced less force during a single-leg horizontal press.

Topics: Activities of Daily Living; Aged; Analysis of Variance; Arthroplasty, Replacement, Knee; Biomechanical Phenomena; Body Height; Body Mass Index; Body Weight; Case-Control Studies; Elasticity; Exercise Therapy; Female; Humans; Isometric Contraction; Knee Prosthesis; Lower Extremity; Male; Middle Aged; Muscle Weakness; Needs Assessment; Range of Motion, Articular; Torque; Weight-Bearing

To evaluate neck flexion, extension, and, especially, rotation strength in women with chronic neck pain compared with healthy controls and to evaluate the repeatability of peak isometric neck strength measurements in patients with neck pain.. Cross-sectional.. Rehabilitation center and physical and rehabilitation medicine department at a Finnish hospital.. Twenty-one women with chronic neck pain and healthy controls matched for sex, age, anthropometric measures, and occupation.. Not applicable.. Peak isometric strength of the cervical muscles was tested in rotation, flexion, and extension.. Significantly lower flexion (29%), extension (29%), and rotation forces (23%) were produced by the chronic neck pain group compared with controls. When the repeated test results were compared pairwise against their mean, considerable variation was observed in the measures on the individual level. Intratester repeatability of the neck muscle strength measurements was good in all the 4 directions tested in the chronic neck pain group (intraclass correlation coefficient range,.74-.94). The coefficient of repeatability was 15N, both in flexion and extension, and 1.8 Nm in rotation. On the group level, improvement up to 10% due to repeated testing was observed.. The group with neck pain had lower neck muscle strength in all the directions tested than the control group. This factor should be considered when planning rehabilitation programs. Strength tests may be useful in monitoring training progress in clinical settings, but training programs should be planned so that the improvement in results is well above biologic variation, measurement error, and learning effect because of repeated testing.

Topics: Adult; Analysis of Variance; Body Height; Body Mass Index; Body Weight; Case-Control Studies; Chronic Disease; Cross-Sectional Studies; Female; Finland; Hand Strength; Head Movements; Humans; Isometric Contraction; Middle Aged; Muscle Weakness; Neck Muscles; Neck Pain; Observer Variation; Physical Therapy Modalities; Range of Motion, Articular; Rotation; Torque

In a prospective study (1993-2000), we measured the isokinetic strength of the quadriceps and hamstring muscles in 31 children aged 5-17 years, on average, 3 (1.5-5) years after treatment for a displaced femoral fracture by external fixation and early mobilization. A group of age-, sex- and weight-matched children without previous injury were used as controls. The hop-index test was used to assess the patient's confidence in the injured limb and was similar in the fractured and unfractured legs as well as in the patients and controls. We measured the peak torque output at 2 angular velocities (60 degrees/s and 180 degrees/s) in the hamstring and quadriceps muscles, using Cybex testing equipment. Torque to body weight ratios were used to compare muscle strength in patients and controls. We found no differences in muscle strength between patients and controls or in the distribution of which leg was stronger, equal or weaker in the patients or controls at any test speed. External fixation and early mobilization seem to prevent residual muscle weakness, which occurs with traction or a cast for femoral fractures in children.

Topics: Adolescent; Body Weight; Case-Control Studies; Casts, Surgical; Child; Child, Preschool; Early Ambulation; External Fixators; Female; Femoral Fractures; Fracture Fixation; Fracture Healing; Functional Laterality; Humans; Male; Muscle Weakness; Prospective Studies; Recovery of Function; Sex Characteristics; Time Factors; Torque; Traction; Treatment Outcome; Weight-Bearing

The purpose of this study was to determine if the elimination of satellite cell proliferation using gamma-irradiation would inhibit normal force recovery after eccentric contraction-induced muscle injury. Adult female ICR mice were implanted with a stimulating nerve cuff on the common peroneal nerve and assigned to one of four groups: 1) irradiation- and eccentric contraction-induced injury, 2) eccentric contraction-induced injury only, 3) irradiation only, and 4) no intervention. Anterior crural muscles were irradiated with a dose of 2,500 rad and injured with 150 in vivo maximal eccentric contractions. Maximal isometric torque was determined weekly through 35 days postinjury. Immediately after injury, maximal isometric torque was reduced by approximately 50% and had returned to normal by 28 days postinjury in the nonirradiated injured mice. However, torque production of irradiated injured animals did not recover fully and was 25% less than that of injured nonirradiated mice 35 days postinjury. These data suggest that satellite cell proliferation is required for approximately half of the force recovery after eccentric contraction-induced injury.

Topics: Animals; Body Weight; Cell Division; Female; Isometric Contraction; Mice; Mice, Inbred ICR; Muscle Fibers, Skeletal; Muscle, Skeletal; Organ Size; Recovery of Function; Satellite Cells, Skeletal Muscle; Torque

The objective of this study was to quantify the relationship between trunk posture and trunk muscle function in a group of young, normal male and female subjects. Ten male and 10 female subjects performed isometric flexion and extension tasks using a trunk dynamometer. Peak isometric torque was recorded in flexion and extension at 10 degrees increments over a sagittal posture range of -20 degrees extension to +50 degrees of flexion. Significant differences in trunk strength (isometric torque) were found between males and females, at various sagittal plane trunk postures, and between flexion (F) and extension (E) tasks. Flexion torque was greatest at 20 degrees to 30 degrees flexion, whereas extension torque was greatest at 50 degrees flexion. Gender-specific differences in trunk strength were markedly reduced when the torque data were normalized by the subject's height multiplied by body weight. The E/F torque ratio showed a relatively linear, over twofold increase with increasing flexion angle, and was significantly greater for female subjects compared with male subjects at most sagittal postures. The baseline trunk isometric strength data provided by this study should help clinicians to use strength testing more precisely and specifically in prevention and diagnosis of patients at risk for back disorders.

Topics: Adult; Biomechanical Phenomena; Body Weight; Electromyography; Female; Humans; Isometric Contraction; Male; Movement; Muscle, Skeletal; Posture; Reference Values; Sex Characteristics; Torque

Numerous models used to investigate the causes of low back pain are based upon the concept of the lever model that considers equilibrium of forces and moments about a single intervertebral joint. Consideration of forces and moments at each intervertebral joint is essential if a more realistic idea of the loading on the spine is to be obtained. This will also allow the role of the curvature of the spine to be investigated. A distributed loading pattern for forces due to body weight for the whole spine has not been investigated before. In this paper, a distributed loading pattern for the whole spine for various postures is investigated and the potential impact on the calculations is discussed.

Topics: Body Weight; Computer Simulation; Humans; Models, Biological; Posture; Rotation; Sensitivity and Specificity; Spine; Stress, Mechanical; Torque; Weight-Bearing

The purpose of this study was to identify quadriceps femoris strength thresholds below which performance on ambulatory tasks is compromised. A second purpose was to evaluate whether self-reported functioning matches evaluated performance of the activities. Subjects (N = 100; age 73 +/- 0.9 years) participated in isometric knee extension strength tests, performed three functional ambulatory tasks (chair rise, gait speed, and stair ascent and descent), and answered standard survey questions assessing physical function. Significant relationships were observed between functional performance and the ratio of isometric leg extension peak torque to body weight (STR/WT) for each activity (p <.0001). For each activity, thresholds of STR/WT between 3.0 and 3.5 N m/kg were observed, below which the likelihood for success was reduced. Thresholds were determined by calculating the value of STR/WT that minimized the classification error. Individuals with a STR/WT < 3.0 N m/kg are at a substantial risk for impaired function in chair rise, gait speed, and stair ascent and descent. Sensitivity and specificity of STR/WT as a predictor of functional success ranged from 76% to 81% and from 78% to 94%, respectively, depending on activity. This is of clinical significance, as the STR/WT thresholds can identify individuals with preclinical disability (beginning to have difficulty with ambulatory tasks) as opposed to those in whom an outright disability is observed. This may be useful for targeting individuals for strengthening interventions and developing specific intervention goals.

Topics: Aged; Body Weight; Differential Threshold; Female; Humans; Isometric Contraction; Male; Muscle, Skeletal; Self Concept; Thigh; Torque

In trotting dogs, the pattern of activity of the obliquely oriented hypaxial muscles is consistent with the possible functions of (i) stabilization against vertical accelerations that cause the trunk to sag in the sagittal plane and (ii) stabilization against forces that tend to shear the trunk in the sagittal plane. To test these hypotheses, we compared the amount of activity of the intercostal and abdominal oblique muscles (i) when dogs carried additional mass (8-15% of body mass) supported over the limb girdles versus supported mid-trunk (test of sagittal bounce), and (ii) when dogs trotted up versus down a 10 degrees slope (test of sagittal shear). In response to the loading manipulations, only the internal oblique muscle responded in a manner that was consistent with stabilization of the trunk against forces that cause the trunk to sag sagittally. In contrast, when the fore-aft forces were manipulated by running up- and downhill, all four of the monitored muscles changed their activity in a manner consistent with stabilization of the trunk against sagittal shearing. Specifically, muscles with a craniodorsal orientation (external oblique and external intercostal muscles) showed an increase in activity when the dogs ran downhill and a decrease when they ran uphill. Muscles with a cranioventral orientation (internal oblique and internal intercostal muscles) exhibited the opposite pattern: increased activity when the dogs ran uphill and decreased activity when they ran downhill. Changes in activity of two extrinsic appendicular muscles, the serratus ventralis and deep pectoralis, during uphill and downhill running were also consistent with the sagittal shearing hypothesis. In contrast, changes in the level of recruitment of the oblique hypaxial muscles were not consistent with stabilization of the trunk against torques that induce yaw at the girdles. Hence, we suggest that the oblique hypaxial muscles of trotting dogs act to stabilize the trunk against sagittal shearing torques induced by limb retraction (fore-aft acceleration) and protraction (fore-aft deceleration).

Topics: Animals; Biomechanical Phenomena; Body Weight; Dogs; Electrodes, Implanted; Electromyography; Locomotion; Muscle, Skeletal; Running; Torque

In the light of experimental results showing significant forward centre of mass (CoM) displacements within the base of support, this study investigated if whole body reaching movements can be executed whilst keeping the CoM fixed in the horizontal axis. Using kinematic simulation techniques, angular configurations were recreated from experimental data imposing two constraints: a constant horizontal position of the CoM and an identical trajectory of the hand to grasp an object. The comparison between recorded and simulated trials showed that stabilisation of the CoM was associated with greater backward hip displacements, which became more marked with increasing object distance. This was in contrast to recorded trials showing reductions in backward hip displacements with increasing distance. Results also showed that modifications to angular displacements were necessary only at the shoulder and hip joints, but that these modifications were within the limits of joint mobility. The analysis of individual joint torques revealed that the pattern and timing of simulated trials were similar to those recorded experimentally. Peak joint torque values showed particularly that keeping the CoM at a constant horizontal position resulted in significantly smaller ankle peak flexor and extensor torques. It may be concluded from this study that 'stabilising' the CoM during human whole body reaching represents a feasible strategy, but not the one chosen by subjects under experimental conditions. Our results also do not support the idea of the CoM as the stabilised reference value for the coordination between posture and goal-directed movements.

Topics: Adolescent; Adult; Biomechanical Phenomena; Body Weight; Computer Simulation; Female; Hand; Hip; Humans; Joints; Male; Mathematics; Movement; Postural Balance; Posture; Pressure; Psychomotor Performance; Time Factors; Torque

To investigate the effects of age on the reciprocal peak torque ratios during knee muscle contractions, 25 elite male soccer players, aged 22.3 +/- 3.8 yr (18-28), volunteered for the present study. The players were grouped as adult (> 21 years, n = 13) and young players (< or = 21 years, n = 12). Maximal concentric (CON) and eccentric (ECC) isokinetic thigh muscle strength was measured at angular velocities of 30 degrees, 180 degrees, 240 degrees and 300 degrees/s. ECC and CON peak torques of knee flexors (hamstring, HAM) and CON peak torques of knee extensors (quadriceps, QUA) in the dominant knee were greater (P < 0.05) in adult players than in young players at 180, 240 and 300 degrees/s. ECC HAM/CON QUA peak torque ratio at 300 degrees/s was greater (P < 0.05) for adult players compared to young players in the dominant knee but not in the nondominant knee. Furthermore, conventional HAM/QUA peak torque ratios of the dominant knee at all angular velocities for ECC contraction were higher (P < 0.05) in adult players than in young players. In conclusion, the findings of the present study indicate that the reciprocal torque ratio is influenced by age in the dominant knee of elite soccer players. Because there was no effect of age for the nondominant leg, the findings of the present study are more likely to be the result of the training background of the players than their age.

Topics: Adolescent; Adult; Age Factors; Aging; Analysis of Variance; Body Mass Index; Body Weight; Humans; Knee; Knee Joint; Male; Muscle Contraction; Muscle, Skeletal; Oxygen Consumption; Range of Motion, Articular; Soccer; Tendons; Thigh; Torque

This paper examines the effects of two glove conditions and selected handle and task characteristics on tightening (clockwise) torques on cylindrical handles in simulated oil rig tasks. Ten males exerted MVC torques with the right hand on nine handles with different length-diameter combinations (3.8, 7.6, and 12.7 cm in length with 3.8, 6.7, and 8.4 cm in diameter) with dry and grease-smeared gloves in two orientations. The results showed a 50% reduction of torque when using grease-smeared glove compared to dry glove; a 15% increase with the long handle compared to the short one; a 25% increase with the medium diameter handle compared to the small one; and a 12% increase with the horizontally oriented handle compared with the vertical one. There were important interaction effects also.

Topics: Adult; Analysis of Variance; Body Height; Body Weight; Chemical Industry; Equipment Design; Gloves, Protective; Hand; Hand Strength; Humans; Industrial Oils; Male; Muscle Contraction; Petroleum; Posture; Stress, Mechanical; Surface Properties; Task Performance and Analysis; Torque; Transducers

This study examined the nutritional and performance status of elite soccer players during intense training. Eight male players (age 17+/-2 years) of the Puerto Rican Olympic Team recorded daily activities and food intake over 12 days. Daily energy expenditure was 3,833+/-571 (SD) kcal, and energy intake was 3,952+/-1,071 kcal, of which 53.2+/-6.2% (8.3 g x kg BW(-1)) was from carbohydrates (CHO), 32.4+/-4.0% from fat, and 14.4+/-2.3% from protein. With the exception of calcium, all micronutrients examined were in accordance with dietary guidelines. Body fat was 7.6+/-1.1% of body weight. Time to completion of three runs of the soccer-specific test was 37.65+/-0.62 s, and peak torques of the knee flexors and extensors at 60 degrees x s(-1) were 139+/-6 and 225+/-9 N x m, respectively. Players' absolute amounts of CHO seemed to be above the minimum recommended intake to maximize glycogen storage, but calcium intakes were below recommended. Their body fat was unremarkable, and they had a comparatively good capacity to endure repeated bouts of intense soccer-specific exercise and to exert force with their knee extensors and flexors.

Topics: Activities of Daily Living; Adipose Tissue; Adolescent; Body Mass Index; Body Weight; Calcium, Dietary; Diet; Dietary Carbohydrates; Dietary Fats; Dietary Proteins; Energy Intake; Energy Metabolism; Glycogen; Humans; Knee Joint; Male; Micronutrients; Motor Skills; Muscle, Skeletal; Nutritional Physiological Phenomena; Physical Endurance; Puerto Rico; Soccer; Torque

The purpose of this study was to develop further normative data for an isokinetic profile for intercollegiate baseball pitchers at 180, 300, and 450 degrees.s-1. Information on isokinetic performance at 450 degrees.s-1 was not found in previously published literature.. Sixteen intercollegiate baseball pitchers volunteered for isokinetic strength testing of internal and external rotators of the shoulder. The testing was conducted at 180, 300, and 450 degrees.s-1; with the pitchers in a position of function (90 degrees/90 degrees).. The subjects were able to reach maximal velocity for each of the speeds tested, including 450 degrees.s-1. These pitchers demonstrated no significant difference between dominant and nondominant arms for peak torque, torque/body weight, work/body weight, or average power (P < 0.05). Torque produced at 0.2 s was significantly greater in the dominant arm compared with the nondominant arm at 450 degrees.s-1 only. Internal rotation values were significantly greater than external rotation values for all areas of comparison. External rotation/internal rotation ratios remained consistent for each speed tested (approximately 0.65).. There is minimal difference in strength values between dominant and nondominant arms of intercollegiate baseball pitchers, with the exception of significantly greater internal rotation peak torque at 0.2 s at 450 degrees.s-1 in the dominant arm. Dominant arm, as well as nondominant arm, ER/IR ratios remain consistent throughout the velocity spectrum. A valid test speed for intercollegiate baseball pitchers appears to be 450 degrees.s-1 when tested before the start of throwing from the pitcher's mound.

Topics: Adolescent; Adult; Baseball; Body Weight; Ergometry; Functional Laterality; Humans; Male; Muscle Contraction; Muscle, Skeletal; Range of Motion, Articular; Reproducibility of Results; Rotation; Shoulder Joint; Torque; Work

Maximal isokinetic concentric (60 degrees/s and 180 degrees/s) and eccentric (60 degrees/s) muscle strength of the external and internal rotator muscles of the shoulder and the flexor and extensor muscles of the elbow was measured in a position resembling spiking and serving in volleyball, on 11 non-injured female volleyball players (first division) and 11 non-active females. In the dominant arm, the volleyball players had significantly higher concentric peak torque of the internal and external rotators and elbow extensors at both velocities, and significantly higher eccentric peak torque of the shoulder internal and external rotators and elbow flexors and extensors, than the controls. In the volleyball group, the concentric internal rotation peak torque at 60 degrees/s was significantly higher in the dominant than in the non-dominant arm. The external/internal strength ratio was significantly lower at 60 degrees/s, but not at 180 degrees/s, in the dominant arm.. The female volleyball players had a higher concentric and eccentric strength in the rotator muscles of the shoulder and in the extensor muscles of the elbow compared to untrained controls in this special test position. There were signs of rotator muscle imbalance at the low test speed, but no signs of weakness of the external rotators, in the dominant arm of the volleyball players.

Topics: Acceleration; Adult; Age Factors; Body Weight; Elbow; Elbow Joint; Female; Functional Laterality; Humans; Muscle Contraction; Muscle, Skeletal; Range of Motion, Articular; Rotation; Shoulder; Shoulder Joint; Sports; Torque

In this population-based study, the relationship between childhood weight and height, and adolescent bone mass and muscle strength have been studied in 39 girls and 48 boys. Total body and femoral neck bone mass measurements (bone mineral content, BMC and bone mineral density, BMD) were made by dual X-ray absorptiometry. Quadriceps muscle strength was measured. Mean age at the time of measurement was 15.1 years for girls and boys. Results were individually linked to data on childhood (birth to 6 years of age) weight and height, taken from community health records. Childhood weight was found to be predictive of adolescent total body BMC (TBMC). However, this was not the case when correlating childhood weight and total body BMD (TBMD), suggesting that growth determines the size of the skeleton, whereas the density within that bone envelope is to a greater extent governed by other factors. Further, in a multiple regression model we found that the combined effect of childhood weight and height was significantly correlated with adolescent quadriceps muscle strength.

Topics: Absorptiometry, Photon; Adolescent; Body Height; Body Weight; Bone and Bones; Bone Density; Female; Femur; Humans; Leg; Male; Menarche; Muscle, Skeletal; Predictive Value of Tests; Sex Characteristics; Torque

We study the influence of the calculation of the trunk gravity correction, in standing position, on the isokinetic trunk flexors and extensors performance of a healthy population. Thirty men and 30 women are subjected to two tests, one with gravity correction, the other without, at angular speeds of 30 degrees/s and 120 degrees/s. In all cases the results with gravity correction show: a significant decrease of Peak Torque (PT) and Power (P) recorded on the trunk flexors and a significant increase of Peak Torque and Power recorded on the trunk extensors. Thus, the flexors/extensors ratios (50%) of both parameters are quite different from the ratios usually referred to in the literature (70%).

Topics: Adult; Back; Body Weight; Ergometry; Exercise Test; Female; Gravitation; Humans; Isometric Contraction; Male; Middle Aged; Muscle Contraction; Muscle Relaxation; Muscle, Skeletal; Posture; Torque