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In sweep rowers, the lower extremities muscle strength translates into the driving force of the boat. Therefore, isokinetic assessment of muscle torque is used by coaches as an indicator of the level of athletes' preparation for competitions. A total of 22 elite sweep rowers performed an isokinetic test of knee joint flexors and extensors, and a test on an asymmetric ergometer with the electromyography measures. Significantly higher quadriceps peak torque was shown during the beginning than the end of the preparatory period (

The study aimed to analyse the effectiveness of two variants of 8-week strength training (hypertrophy, strength) with different modes of resistance. Healthy male subjects (n=75) were allocated to five groups of equal size: hypertrophy training with a variable cam (Hyp-Cam), hypertrophy training with disc plates (Hyp-Disc), maximal strength training with a variable cam (Str-Cam), maximal strength training with disc plates (Str-Disc), and a control group (CG). The Hyp-Cam and Str-Cam groups trained with a machine where the load was adjusted to the strength capabilities of the elbow flexors. The Hyp-Disc and Str-Disc groups trained on a separate machine in which a load was applied with disc plates. The CG did not train. All groups were assessed for changes and differences in one-repetition (1RM) lifts, isokinetic muscle torque, arm circumference and arm skinfold thickness, and plasma creatine kinase (CK) activity. Within the 8-week training period the 1RM increased (p.05) or Str-Disc (0.2 cm; p>.05) group. Skinfold thickness of the biceps and triceps decreased more within the 8-week period in Str-Cam (by 1.1 and 2.1 cm; p.05 and p.05 and p.05). The 8-week hypertrophy training with a variable cam results in greater peak muscle torque improvement than in the other examined protocols, with an insignificant increase in training-induced muscle damage indices.

Background: Muscle weakness is characteristic of knee osteoarthritis. Muscle steadiness may be an important adjunct to knee muscle strength in improving physical function in knee osteoarthritis. However, the role of muscle steadiness is uncertain. Aims: To determine the associations of knee extensor muscle steadiness with maximal voluntary torque and physical function in patients with knee osteoarthritis. Methods: Baseline data from 177 patients in a randomized clinical trial were used. Isokinetic knee extension torque was processed into maximal voluntary torque [Nm]. Muscle steadiness was expressed as the coefficient of variance [%] and as peak power frequency [Hz]. Physical function was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index, the Get-Up-and-Go and Stair-climb tests. Associations were determined using regression analyses and adjusted for confounders. Findings: Lower muscle steadiness (i.e., higher coefficient of variance and peak power frequency) was associated with lower maximal voluntary torque (B = − 7.38, [−10.8, −3.95], R2 = 0.10 and B = −14.71, [−28.29, −1.13], R2 = 0.03, respectively). Higher coefficient of variance was associated with lower self-reported physical function (B = 1.14, [0.11,2.17], R2 = 0.03) and remained significant after adjusting for potential confounders. Peak power frequency was not associated with physical function. Interpretation: Low muscle steadiness was weakly associated with low muscle strength and poorer self-reported physical function. Muscle steadiness and muscle strength seem to be different attributes of muscle function. There is no convincing evidence that muscle steadiness is an important adjunct in studying physical function in patients with knee osteoarthritis.

The primary objective was to compare hip and knee isometric muscle strength between individuals with a first-time acute lateral ankle sprain and controls. A secondary objective was to investigate hip and knee isometric muscle strength three months post-injury.Cross-sectional and prospective follow-up components.Laboratory environment.Forty-two participants (21 acute lateral ankle sprain and 21 controls) matched for age, sex, physical activity and leg dominance participated.Hip and knee isometric muscle torque was assessed using a rigidly fixated hand-held dynamometer. Testing in acute lateral ankle sprain participants was performed within four weeks of injury and three months post-injury. Controls were tested at one timepoint.There were no differences in hip or knee isometric muscle torque between acute lateral ankle sprain and control participants (mean differences0.08). Hip and knee isometric muscle torque in acute ankle sprain participants did not differ between baseline and three months post-injury testing (mean difference0.06).Proximal lower limb isometric strength is not impaired within the first three months of sustaining a first-time lateral ankle sprain injury. This implies that hip and knee isometric strength deficits in individuals with CAI may occur at some later stage.

Background Identifying the characteristics of physical function and muscle strength related to swing velocity is necessary for improving batting performance. The purpose of this study was to identify the factors related to swing velocity in youth baseball players. Methods 191 youth baseball players aged 7-13 years old participated and were divided into the Tee Ball (˂9.5 years) and Major (≥9.5 years) divisions. We measured the swing velocity for batting performance, medicine ball (MB) back throw and modified star excursion balance test (SEBT) for physical function, and hip muscle torque for lower extremity muscle strength. Results Height and MB back throw (β=0.403 and 0.380) for physical function (R2=0.646), and height and internal rotation (IR) torque of the step leg (β=0.620 and 0.216) in lower extremity muscle strength (R2=0.616) were all extracted as related independents for the multiple regression analysis on swing velocity in all subjects. Additionally, height, MB back throw and modified SEBT in the pivot leg (β=0.420, 0.324 and 0.218) for the Major division (R2=0.579), and IR torque of the pivot leg and step leg (β=0.555 and 0.525) for the Tee Ball Division (R2=0.568) were selected. Conclusions Swing velocity was related to height, MB back throws on physical function, and IR torque of the stepping leg in lower extremity muscle strength in youth baseball players. Therefore, the explosive power and strength for stopping the body opposite to the hitting direction are considered necessary to increase the swing velocity.

Purpose: This study aimed to determine the contribution of metabolic, cardiopulmonary, neuromuscular, and biomechanical factors to the energy cost (ECR) of graded running in well-trained runners. Methods: Eight men who were well-trained trail runners (age: 29 [10] y, mean [SD]; maximum oxygen consumption: 68.0 [6.4] mL·min−1·kg−1) completed maximal isometric evaluations of lower limb extensor muscles and 3 randomized trials on a treadmill to determine their metabolic and cardiovascular responses and running gait kinematics during downhill (DR: −15% slope), level (0%), and uphill running (UR: 15%) performed at similar O2 uptake (approximately 60% maximum oxygen consumption). Results: Despite similar O2 demand, ECR was lower in DR versus level running versus UR (2.5 [0.2] vs 3.6 [0.2] vs 7.9 [0.5] J·kg−1·m−1, respectively; all P r2 = .63; P = .018). Importantly, while ECR was correlated with heart rate, cardiac output, and arteriovenous O2 difference in UR (all r2 > .50; P r2 > .58; P Conclusion: The determining physiological factors of ECR might be slope specific, mainly metabolic and cardiovascular in UR versus mainly neuromuscular and mechanical in DR. This possible slope specificity of ECR during incline running opens the way for the implementation of differentiated physiological evaluations and training strategies to optimize performance in well-trained trail runners.

This study explores the cardiorespiratory and muscular fatigue responses to downhill (DR) vs uphill running (UR) at similar running speed or similar oxygen uptake (⩒O2). Eight well-trained, male, t...

Objectives We compared hip and knee isometric muscle torque between individuals with chronic ankle instability (CAI), those who have sustained one ankle sprain with no ongoing problems (copers) and healthy controls. Our secondary objective was to compare balance between groups and investigate the relationship between muscle torque and balance. Design Cross-sectional study. Methods 22 CAI, 20 copers and 22 uninjured participants were tested. Isometric torque (normalised to body mass (Nm/kg)) was measured using a rigidly-fixated hand-held dynamometer. Balance was assessed with the Y-balance test. Results Knee and hip flexor and extensor, and hip adductor and abductor muscle torque was less in individuals with CAI compared to controls (standardised mean difference (SMD) >1.2). Hip and knee flexor and extensor muscle torque was less in CAI participants than copers (SMD: 0.69–1.1). Hip external and internal rotator torque did not differ between groups. There was no difference in hip or knee muscle torque between controls and copers (SMD: 0.01–0. 54). Balance was impaired in CAI participants compared to copers and controls in all directions. There was a strong positive correlation between posterolateral Y-balance test performance and torque of the hip adductors (r = 0.53), flexors (r = 0.52) and extensors (r = 0.50). Conclusions Individuals with CAI have weak knee and hip muscles compared to copers and controls. Hip strength was shown to be related to posterolateral balance performance. Future studies may investigate the effect of hip and knee strengthening exercise on ongoing ankle problems, such as episodic giving way in individuals with CAI.

The aim of this study was to determine the effect of muscular strength, strength asymmetries, and fatigue on the speed and accuracy of an instep kick in soccer players. We measured ball velocity (BV) and kicking accuracy (KA) in the preferred (PL) and non-preferred leg (NPL) before (PRE) and after (POST) physical load in the PL. Maximum peak muscle torque of the knee extensors and flexors in the PL and NPL as well as ipsilateral knee flexors and knee extensors ratio (H:Q ratio) for both legs were assessed. BV was significantly decreased in POST physical load (5.82%, BVPRE=30.79±1.70 m·s−1, BVPOST=29.00±1.70 m·s−1, t19=3.67, p=0.00, d=1.05). Instep kick accuracy after the physical load worsened by an average of 10% in the most accurate trials. Results revealed a significant decrease in instep kick accuracy after physical loading (KAPRE=2.74±0.70 m, KAPOST=3.85±1.24 m, t19=–3.31, p=0.00, d=1.10). We found an insignificant correlation between H:Q ratio and KA in PRE test value, whereas a lower ipsilateral ratio (higher degree of strength asymmetry) in the POST physical load significantly correlated with KA in all angular velocities (r=–0.63 up to –0.67, p=0.00).

Introduction . The aim of the study was to determine the changes in the peak torque of the knee extensors and flexors of the dominant lower limb, the shoulder internal and external rotators of the dominant upper limb, and the shoulder extensors and flexors of the dominant upper limb as well as the changes in jump height in volleyball players during the annual training macrocycle. Material and methods . The study involved 13 volleyball players from a Polish second-league team. The measurements were performed five times: before the preparation period (T1), at the beginning of the competitive season (T2), in the middle (T3) and at the end of the first competition period (T4), and after the competitive season (T5). The torque of the knee muscles and shoulder rotators was measured in isokinetic conditions, and the torque of the shoulder extensors and flexors was assessed in isometric conditions. Jumping ability was tested using a piezoelectric platform. Results . We observed statistically significant differences (p < 0.05) in jump height and relative peak torque between the measurements, except for the torque of the shoulder external rotators and flexors. The results of multiple factor analysis based on 5 sets composed of 5 strength variables revealed differences between subjects and measurement sessions. Conclusions . The results obtained indicate that strength and jumping ability should be assessed regularly during the competitive season. The findings of the study suggest that it is necessary to modify the training methods used during the preparation period and individualize the training in the final phase of the competition period.

Introduction Kinesio taping consists of the attachment of a thin elastic tape over specific muscles, the thickness of which is similar to that of the epidermis. Objective The aim of the present study was to compare the effect of Kinesio taping and placebo taping on muscle torque, muscle activity and jumping performance soccer players. Methods Thirty athletes were randomly allocated to two groups (Group A: Kinesio taping and Group B: placebo taping). The participants were instructed to perform the Hop test's and were submitted to an isokinetic evaluation of the knee extensors as well as an electromyographic evaluation of the retus femoris muscle of the dominant lower limb. Next, Kinesio taping was performed for the activation of the rectus femoris muscle in Group A and placebo taping was performed in Group B. The participants were reevaluated 30 minutes after taping and 24 hours after the first evaluation using the same tests. Intra-group and inter-group comparisons were made considering the three evaluation times. Results No statistically significant differences were found between groups at any evaluation time regarding the Hop test's, root mean square of the electromyographic signal or peak torque of the knee extensors of the dominant lower limb (p>0.05). Conclusion Kinesio taping for the activation of the rectus femoris muscle has no effect on peak muscle torque, muscle activity or jumping performance among soccer players.

International audience; Purpose: Perception of action capabilities can be altered by changes in sensorimotor processes, as showed in previous works in populations dealing with regular and pathological sensorimotor deficits. Misestimating changes in performance ability could lead to risky behavior, injury, and/or reduced performance. However, the relationship between sensorimotor processes, the action-perception coupling, and the related anatomical structures is still a matter of debate. We investigated whether changes in the muscle-tendon system's mechanical properties experimentally induced by eccentric contractions could alter the action-perception coupling (APC) in a reaching-to-grasp task, in which the participants estimated the maximal distance they predicted that they would able to reach a glass.Methods: Based on their repartition, volunteers performed a conditioning session the first day: a series of isokinetic elbow extension in passive condition (control group, n = 11) or when performing elbow flexors eccentric contractions (eccentric group, n = 11). Performance estimates and actual performances in a reaching-to-grasp task were completed before, and immediately, 24 hours and 48 hours after the conditioning session. Alterations of musculo-articular mechanical properties were assessed through global joint stiffness (joint passive torque through load/unload cycles) and local stiffness (muscle elastography).Results: The results showed that the APC related to reaching-to-grasp performance was not impacted by post-exercise changes in mechanical properties of the musculo-articular system.Conclusion: These findings emphasize the central dimension of sensorimotor processing instead of peripheral structures to investigate the APC for an altered sensorimotor environment.

The link between age-related changes in muscle strength and gait is unclear. We tested if knee extensor functional demand differs by age and physical activity status and if functional demand increases with walking speed or after exercise. Gait and knee extensor muscle torque were collected from young adults and highly and less active older adults before and after treadmill walking. Functional demand was the ratio of knee moments during gait to knee extensor muscle torques estimated from participant-specific torque–velocity curves. Functional demand at the peak knee flexion moment was greater in less active older adults than young adults (29.3% [14.3%] vs 24.6% [12.1%]) and increased with walking speed (32.0% [13.9%] vs 22.8% [10.4%]). Functional demand at both knee extension moments increased ∼2% to 3% after exercise. The low functional demand found in this study suggests that healthy adults maintain a reserve of knee extensor strength.

Background Many studies have investigated the correlation between muscle torque and joint position sense (JPS), but few studies have been performed on the correlation between torque ratio and JPS. Objective The aim of this study was to investigate JPS and muscle torque ratios of agonist and antagonist muscles in the ankle and knee joints of young adults. Methods A total of 38 right handed healthy participants, 12 males and 26 females, were recruited. All participants measured their peak torque of knee flexor/extensor and ankle dorsiflexor/plantar flexor by using a Biodex system. They also used the Biodex to assess the proprioception through active joint reposition sense test in knee and ankle joint. Peak torque of each muscle, agonist/antagonist torque ratio and JPS error were collected, and Pearson's correlation analysis was used to examine correlations between peak torque, torque ratio and JPS error. Results For knee joints, correlations were found between flexion and extension torque, extension torque and torque ratio, and torque ratio and JPS error (r= 0.825/p= 0.000, r=-0.482/p= 0.002, and r=-0.685/p= 0.000, respectively). For ankle joints, correlations were found between dorsiflexion and plantar flexion torques, plantar flexion torque and torque ratio, plantar flexion torque and JPS, and torque ratio and JPS (r= 0.654/p= 0.000, r=-0.621/p= 0.000, r=-0.563/p= 0.000, and r=-0.761/p= 0.000, respectively). Conclusions JPS error of lower extremity joint may be more related with agonist/antagonist torque ratio rather than peak torque. Therefore, people who will have training for reducing JPS error need to consider torque ratio, too.

Older females experience higher rates of disability than males, potentially due to sex-specific differences in gait and muscle function. The authors evaluated the effects of age and physical activity (PA) on gait mechanics and knee extensor muscle function in males and females. Three groups of 20 individuals (each 10 females) participated: young (21–35 y) and highly and less active older (55–70 y) adults. Knee extensor strength and joint mechanics during preferred speed gait were collected before and after 30 minutes of walking. Age by sex and PA by sex interactions indicated older and less active older females had lower concentric knee extensor muscle power and larger hip extension moments than males. After 30 minutes of walking, older less active adults had larger decreases in knee extensor power than their highly active older counterparts, and older adults of both sexes had decreases in ankle dorsiflexion moments while young adults did not. These results suggest that older, particularly less active, adults are susceptible to knee extensor muscle fatigue from moderate activity. For older adults, high levels of PA may be necessary to preserve gait mechanics in response to a bout of exercise. This new information may be important for targeting interventions in at-risk older adults.

The temporal structure, or complexity, of muscle torque output reflects the adaptability of motor control to changes in task demands. This complexity is reduced by neuromuscular fatigue during intermittent isometric contractions. We tested the hypothesis that sustained fatiguing isometric contractions would result in a similar loss of complexity. To that end, nine healthy participants performed, on separate days, sustained isometric contractions of the knee extensors at 20% MVC to task failure and at 100% MVC for 60 seconds. Torque and surface EMG signals were sampled continuously. Complexity and fractal scaling were quantified by calculating approximate entropy (ApEn) and the detrended fluctuation analysis (DFA) α scaling exponent. Global, central and peripheral fatigue were quantified using maximal voluntary contractions (MVCs) with femoral nerve stimulation. Fatigue reduced the complexity of both submaximal (ApEn from 1.02 ± 0.06 to 0.41 ± 0.04, P < 0.05) and maximal contractions (ApEn from 0.34 ± 0.05 to 0.26 ± 0.04, P < 0.05; DFA α from 1.41 ± 0.04 to 1.52 ± 0.03, P < 0.05). The losses of complexity were accompanied by significant global, central and peripheral fatigue (all P < 0.05). These results demonstrate that a fatigue-induced loss of torque complexity is evident not only during fatiguing intermittent isometric contractions, but also during sustained fatiguing contractions.

Introduction. The aim of the current study was to examine the relationship between knee and elbow isometric muscle torque values and the results obtained in special and specific exercises in young weightlifters. Material and methods. The study involved eight young weightlifters (age: 19.9 ± 4.3 years; height: 176.8 ± 10.6 cm; weight: 69.0 ± 19.7 kg - pretest, 70.9 ± 21.6 - posttest). Their performance put them in the second and third top classes of weightlifters their age according to the Polish norms for weightlifting (the so-called ‘national class’ and ‘first class’ in the Polish system, which are lower than the ‘international class’). The differences between the values obtained in the first measurement of torque performed at the beginning of the preparation period and those obtained at the beginning of the immediate pre-competition period were compared with the differences in the maximal load lifted in special and specific exercises. Results. The training that the weightlifters underwent during the preparation period caused a significant increase in the relative torque values of the knee extensors (0.56 Nm/kg on average, p ≤ 0.047) and those of the elbow flexors (0.35 Nm/kg, p ≤ 0.0002). Significant differences (p ≤ 0.05) were observed between the results obtained in all of the special and specific exercises examined. A statistically significant relationship was also found between the changes in relative torque values and the results achieved in special and specific exercises. Conclusions. The regression equations derived in the study can help predict sports performance outcomes based on the results of laboratory tests.

Background:Long-term maintenance of sports participation is important for young men undergoing anterior cruciate ligament (ACL) reconstruction. Identifying biomechanical characteristics in patients who achieve this goal can assist in elaborating rehabilitation programs and in identifying successful recovery, but this has rarely been investigated.Purpose:To test the association between maintenance of sports participation at 5 to 10 years after ACL reconstruction and measures of force production and landing biomechanics in men.Study Design:Cross-sectional study; Level of evidence, 3.Methods:A total of 30 men who underwent isolated ACL reconstruction were examined. At 5- to 10-year follow-up, associations were tested between reported outcomes of sports maintenance and objective biomechanical measures. The biomechanical tests included isokinetic knee torque and lower limb kinetics and kinematics during landing tasks. Measurements for each limb were conducted separately, and side-to-side symmetry indices (SI) were calculated. Subgroups included SI greater than +10% (ie, extreme positive), SI lower than –10% (ie, extreme negative), and SI between –10% and +10% (ie, symmetric).Results:At follow-up, concentric knee torque in the operated limb correlated with Tegner and Marx scores ( r = 0.42-0.47; P ≤ .05). Regarding the SI of knee torque, the highest Tegner, Marx, and KOOS (Knee injury and Osteoarthritis Outcome Score) results were associated with symmetry, as opposed to patients with extreme positive or extreme negative SIs ( P < .05). As for landing kinematics, Tegner score negatively correlated with knee range of motion (ROM) in the operated limb ( r = –0.38; P ≤ .05). With regard to SI, hip and knee ROM correlated with Tegner, IKDC, and KOOS scores ( r = 0.41-0.51; P ≤ .05). Specifically, the highest sports participation levels were associated with achieving symmetric hip and knee ROM but also with extreme positive SIs, as opposed to patients with extreme negative SIs ( P < .03), indicating substantially higher ROM in the uninjured limb as compared with the operated limb.Conclusion:At 5 to 10 years after ACL reconstruction, maintenance of sports participation was associated with symmetric side-to-side concentric knee torque and with producing greater attenuation of hip and knee ROM during the drop jump landing in the operated limb. Therefore, eccentric load programs that can improve attenuation-phase kinematics during landing tasks may be valuable in addition to concentric training and may facilitate enhanced long-term outcomes.

Introduction. In order to help volleyball players achieve superior results, their coaches are constantly seeking new training methods. One of the methods used to improve the effectiveness of the training that is being implemented is conducting tests which make it possible to assess the player’s locomotor system in terms of its motor and biomechanical functions. The aim of the study was to determine the torque of the knee flexor and extensor muscles of volleyball players in three stages of the annual macrocycle. Material and methods. The study involved 14 volleyball players. Torque was assessed using the BIODEX System 4 Pro at the angular velocities of 60°/s and 180°/s, in three periods of the annual training macrocycle. Results. After the preparatory training period, there was a statistically significant increase in the torque of the flexor and extensor muscles of the lower limbs, both for the lower velocity (p ≤ 0.02 for the right limb and p ≤ 0.024 for the left limb) and the higher one (p ≤ 0.03 for the right limb and p ≤ 0.034 for the left limb). After the preliminary round, statistically insignificant changes were found for the torque values obtained at both velocities. Conclusions. The study showed that frequent monitoring of players can help assess their strength capacity in a more reliable way. The results of such measurements carried out in different periods of the volleyball season can help evaluate the players’ strength at a given moment, verify and modify the training methods which are being used, and approach each player individually.

WOS: 000446805000006 PubMed ID: 25960982 After anterior cruciate ligament (ACL) reconstruction, which muscle groups are more affected from frequently developing thigh muscle atrophy is a matter of debate. We evaluate the effect of thigh circumference difference between patients' knees who were administered the ACL reconstruction with hamstring tendon autograft and intact knees, on torque between the hamstring and quadriceps muscles. Fifty-five patients at least 6 months follow-up period available were included in our study. Power measurements of quadriceps and hamstring muscle groups in patients' extremities were done by using isokinetic dynamometer. The maximum torque values at 60 degrees/sec, 240 degrees/sec in frequency, positions of flexion and extension were determined. In accordance with our findings it is still possible to encounter the thigh atrophy in average 28 months after ACL reconstruction surgery even under physical rehabilitation programs and appropriate follow-up. It is inevitable for the clinician to consider these changes in diagnosis and rehabilitation stages. It can't be ignored that muscle weakness mechanisms developing in the thigh circumference vary according to the thigh muscle group and knee flexors play an important role in thigh atrophy when determining an appropriate rehabilitation program after reconstruction application.

International audience; We examined if experts and novices show different utilization of the torque components impulses during dart throwing. Participants threw darts continuously at a dartboard aiming for the centre (target bull’s eye). The upper-limb joint torque impulses were obtained through inverse dynamics with anthropometric and motion capture data as input. Depending on the joint degree of freedom (DOF) and movement phase (acceleration and follow-through), three main strategies of net torque (NET) impulse generation through joint muscle (MUS) and interaction (INT) torque impulses were highlighted. Firstly, our results showed that the elbow flexion–extension DOF leads the movement according to the joint leading hypothesis. Then, considering the acceleration phase, the analysis revealed differences in torque impulse decomposition between expert and novices. For the glenohumeral (GH) joint abduction–adduction and for wrist flexion, the INT torque impulse contributed positively to NET joint torque impulse in the group of experts unlike novices. This allowed to lower the necessary MUS torque impulse at these DOFs. Also, GH axial rotation was actively controlled by muscle torque impulse in the group of experts. During the follow-through, the experts used the INT torque impulse more proficiently than novices to break the elbow extension. The comparison between experts and novices through inverse dynamics document the link between the exploitation of interaction torques impulses and expertise in dart throwing for which the main objective is precision rather than velocity.

The temporal structure, or complexity, of muscle torque output decreases with neuromuscular fatigue. The role of central fatigue in this process is unclear.We tested the hypothesis that caffeine administration would attenuate the fatigue-induced loss of torque complexity.Eleven healthy participants performed intermittent isometric contractions of the knee extensors to task failure at a target torque of 50% maximal voluntary contraction, with a 60% duty factor (6-s contraction, 4-s rest), 60 min after ingesting 6 mg·kg caffeine or a placebo. Torque and surface EMG signals were sampled continuously. Complexity and fractal scaling of torque were quantified using approximate entropy (ApEn) and the detrended fluctuation analysis (DFA) α scaling exponent. Global, central, and peripheral fatigue was quantified using maximal voluntary contractions with femoral nerve stimulation.Caffeine ingestion increased endurance by 30% ± 16% (mean ± SD; P = 0.019). Complexity decreased in both trials (decreased ApEn, increased DFA α; both P0.01), as global, central, and peripheral fatigue developed (all P0.01). Complexity decreased significantly more slowly after caffeine ingestion (ApEn, -0.04 ± 0.02 vs -0.06 ± 0.01 (P = 0.004); DFA α, 0.03 ± 0.02 vs 0.04 ± 0.03 (P = 0.024)), as did the rates of global (-18.2 ± 14.1 vs -23.0 ± 17.4 N·m·min, P = 0.004) and central (-3.5 ± 3.4 vs -5.7 ± 3.9 %·min, P = 0.02) but not peripheral (-6.1 ± 4.1 vs -7.9 ± 6.3 N·m·min, P = 0.06) fatigue.Caffeine ingestion slowed the fatigue-induced loss of torque complexity and increased the time to task failure during intermittent isometric contractions, most likely through central mechanisms.

BACKGROUND: Although a number of studies have compared the influence of different electrical pulse parameters on maximum electrically induced torque (MEIT) and discomfort, the role of phase duration has been poorly investigated. OBJECTIVE: To examine the variation in muscle torque and discomfort produced when electrically stimulating quadriceps femoris using pulsed current with three different phase durations in order to establish whether there are any advantages or disadvantages in varying the phase duration over the range examined. METHOD: This is a two repeated-measures, within-subject study conducted in a research laboratory. The study was divided into 2 parts with 19 healthy young adults in each part.In part 1, MEIT was determined for each phase duration (400, 700, and 1000 µs), using a biphasic pulsed current at a frequency of 50 Hz. In part 2, stimulus amplitude was increased until the contractions reached 40% of maximum voluntary isometric contraction (MVIC) and the associated discomfort produced by each phase duration was measured. RESULTS: In part 1 of the study, we found that the average MEITs generated with each phase duration (400, 700, and 1000 µs) were 55.0, 56.3, and 58.0% of MVIC respectively, but the differences were not statistically significant (p=.45). In part 2, we found a statistically significant increase in discomfort over the same range of phase durations. The results indicate that, for a given level of torque production, discomfort increases with increasing phase duration (p=.008). CONCLUSIONS: Greater muscle torque cannot be produced by increasing the stimulus phase duration over the range examined. Greater discomfort is produced by increasing the stimulus phase duration.

INTRODUÇÃO: A influência dos efeitos do calor no torque em indivíduos de ambos os gêneros é desconhecida, principalmente quando associado à estimulação elétrica. OBJETIVOS: Analisar o efeito da diatermia por ondas curtas no torque do músculo quadríceps femoral gerado pela contração voluntária e eletricamente induzida em indivíduos assintomáticos de ambos os gêneros e avaliar o desconforto gerado pela corrente elétrica. MÉTODOS: Participaram do estudo 26 voluntários, onde foi avaliada a capacidade de produção de torque em um dinamômetro isocinético através de contrações isométricas voluntárias máximas (CIVM) e eletricamente induzida (TEI). Os voluntários foram submetidos a quatro momentos: mensuração do torque através de contração voluntária, contração voluntária após aplicação do calor, contração eletricamente induzida e contração eletricamente induzida após aplicação do calor. O desconforto sensorial durante a estimulação elétrica foi avaliado com a escala visual analógica (EVA). RESULTADOS: O torque no sexo masculino foi maior quando submetido à aplicação da corrente elétrica associado ao calor (p = 0,030). Em relação ao desconforto gerado pela corrente elétrica, foi observado aumento no sexo feminino quando associado ao calor (p = 0,044) comparado ao sexo masculino. CONCLUSÃO: A diatermia por ondas curtas não influenciou o torque produzido pela contração voluntária, porém houve aumento do torque eletricamente induzido (TEI) após aplicação de calor em indivíduos do sexo masculino e aumento do desconforto sensorial gerado pela corrente apenas nos sujeitos do sexo feminino. INTRODUCTION: The influence of the heat effects on muscle torque in males and females is still unknown, especially when associated with electrical stimulation. OBJECTIVES: To assess the effects of shortwave diathermy on voluntary and electrically induced torque in healthy males and females, and to assess the discomfort produced by electrical stimulation. METHODS: Twenty-six subjects participated in the study. Voluntary and electrically induced torque was assessed using an isokinetic dynamometer. The subjects were asked to attend 4 different sessions: measurement of maximal voluntary contraction (MVC); MVC after SWD; maximal electrically induced torque (MEIT); MEIT after SWD. Discomfort during MEIT was measured using a visual analogue scale. RESULTS: MEIT was higher in males after SWD (p = 0.030) Females presented more discomfort during MEIT after SWD application (p = 0.044) when compared to males. CONCLUSION: SWD did not affect the MVC; however, there was increase in MEIT after SWD in males and discomfort increase in females.

The greater torque generation capacity of muscles when contracted alone than in combination with contralateral muscles, characterizes the bilateral limb deficit (BLD) phenomenon. Few studies have explored the BLD in dynamic movements, because isometric actions are considered ideal for evaluating strength. Therefore, the aim of this study was to compare BLD between isometric and concentric actions of the knee extensors. Eleven healthy young men (age = 20.6 ± 1 yrs; weight = 71.4 ± 6.4 kg; height = 174.4 ± 7 cm) volunteered to participate. Initially, subjects visited the laboratory for familiarization with the test protocols. On two subsequent randomized days they performed a test protocol with either a unilateral (right and left limbs) or bilateral condition, with 48 h rest between. The test protocol was composed of five isokinetic concentric actions of the knee extensors at 60 ◦ /s and three isometric actions at a 60 ◦ angle of knee flexion. The greatest peak torque of the two conditions was used for analyses. Both muscle actions demonstrated greater values unilaterally ( p 0.05). Therefore, if muscle torque production is greater unilaterally, athletes and coaches may utilize unilateral exercises to increase training loads.

The purpose of this study was to quantify and compare Resultant Muscle Torque (RMT) and muscle activation (EMG) pattern, during resistance exercise comprising eight repetitions maximum (8 RM) biceps curl with elastic resistance and free weight exercise. Sixteen male and female recreationally active subjects completed 8 RM biceps curl by each of three modalities of resistance exercise: (i) dumbbell (DB), (ii) elastic tubing with original un-stretched length at the commencement of contraction (E0), and (iii) elastic tubing with 30% decrement of original length (E30) at the commencement of contraction. The magnitude of muscle activation, external force, acceleration as well as range of motion (ROM) were quantified and synchronised by specific software. The data were collected from all eight repetitions but the first (initial), the fifth (middle) and the eighth (last) repetitions were selected for further data analysis. Each selected repetition was partitioned into a concentric and eccentric phase an...

This study was conducted to identify factors other than morphological muscle strength factors that affect injured and uninjured sides of knee flexors with anterior cruciate ligament (ACL) lesions.The study population consisted of 22 patients with ACL lesions. Their hamstring muscle volume was measured on MRI, and muscle torque per muscle volume was calculated as the peak torque of knee flexion divided by hamstring muscle volume.The mean muscle torque per unit volume of hamstrings in patients with ACL rupture was 0.09 ± 0.02 Nm/cm(3) at 60°/s and 0.08 ± 0.01 Nm/cm(3) at 180°/s on the injured side, and 0.11 ± 0.02 Nm/cm(3) at 60°/s and 0.08 ± 0.01 Nm/cm(3) at 180°/s on the uninjured side. The mean muscle torque per unit volume of hamstrings in control subjects was 0.11 ± 0.02 Nm/cm(3) at 60°/s and 0.08 ± 0.03 Nm/cm(3) at 180°/s. One-factor ANOVA analysis found no significant differences between the three groups at either flexion velocity.Neurological dysfunction does not appear to exist in knee flexor muscles after ACL injury, unlike the quadriceps. Since the mechanism of muscle weakness will differ depending on the muscle, it is important for clinicians to take this discrepancy into consideration.II.

We hypothesized that patella eversion during total knee arthroplasty (TKA) reduces early return of active knee extension and flexion, quadriceps muscle strength, and postoperative pain. In 100 conventional TKA knees and 100 minimally invasive TKA (MIS TKA) knees, we compared knee range of motion (ROM), postoperative pain, and quadriceps muscle strength at 1 day, 4 days, 1 week, 2 weeks, 3 weeks, 4 weeks, 12 weeks, 1 year, and 5 years after surgery. The differences of surgical approach between MIS TKA and conventional TKA of this study are length of skin incision with subcutaneal flap and patella eversion. In MIS TKA, skin incision is shorter than conventional TKA. Furthermore, patella is not everted in MIS TKA procedure. There were no significant differences in preoperative factors. Postoperative improvement of ROM, postoperative muscle strength recovery, and postoperative improvement of visual analog scale were faster in patients with MIS TKA when compared to that in patients with conventional TKA. On the other hand, no significant difference was observed in complication, 5-year clinical results of subjective knee function score, and the postoperative component angle and lower leg alignment. These results indicate that patella eversion may affect muscle strength recovery and postoperative pain.

The purpose of this study was to evaluate motor unit recruitment in the quadriceps femoris (QF) after anterior cruciate ligament (ACL) rupture and repair. Subjects included 24 patients at ≥ 18 months after ACL reconstruction and 22 control subjects with no history of knee injury. A series of cross-sectional magnetic resonance images were obtained to compare the QF of patients' injured side with that of their uninjured sides and that of uninjured control subjects. Muscle torque per muscle volume was calculated as isokinetic peak torque divided by QF muscle volume (cm(3)). The mean muscle torque per unit volume of the injured side of patients was not significantly different from that of the uninjured side or control subjects (one-way ANOVA) Results of the present study were contrary to the results of a previous study that evaluated patients at ≤ 12 months after ACL reconstruction. The present study found that high-threshold motor unit recruitment was restored at ≥ 18 months after ACL reconstruction. Thus, clinicians must develop techniques that increase the recruitment of high-threshold motor units in the QF from the period immediately after the injury until approximately 18 months after ACL reconstruction.

the aim of this study was to assess muscle torque, total volume, and cross-sectional area, and lower limb function of the quadriceps muscle in women with unilateral patellofemoral pain syndrome (PFPS).twenty-four women with unilateral patellofemoral pain participated in the study, with each subject acting as their own internal control by using the unaffected limb. quadriceps muscle torque was measured with the Isomed 2000. The total volume and cross-sectional area (CSA) of the quadriceps muscle were measured by using magnetic resonance imaging. Lower limb function was assessed by hop and step-down tests.there was a significant difference in the total volume (P0.05) and in the cross-sectional area (P0.05) of the quadriceps muscle between affected and unaffected sides. There was a significant difference in the peak torque of the quadriceps muscle at 60°/s between affected and unaffected sides (P0.05). There were significant correlations between quadriceps largest CSA and volume on the affected side (P0.05) and on the unaffected side (P0.05). There were significant negative correlations between the smallest CSA and the peak torque at 180°/s (P0.05) and at 60°/s (P0.05) on the affected side.decreased torque, total volume, and CSA of the quadriceps muscle are presented in unilateral with PFPS although cause or effect cannot be established. Large prospective longitudinal studies are needed to detect the changes in the muscle structure and to establish whether these features are a cause of PFPS.

The aim of this work was the determination of the cycloergometer exercises influence on the lower limbs power changes and height of rise of the body mass centre, measured in CMJ (counter movement jump) and performed on a dynamometric platform. Forty-three students of the University of Physical Education took part in the study. They were divided into 4 groups. The cycloergometer training encompassed 5 intermittent efforts parted by 2min intervals. Students performed: group M10 – maximal efforts with the load equal 10% of body mass; group M5 – maximal efforts with the load of 5% body mass; group W80 – 3min efforts with the power of 250 W, singular effort work equal 45 kJ, pedalling rate – 80 rpm; group W45 – 3min efforts with the power of 250 W, individual effort work equal 45 kJ, pedalling rate of 45 rpm. The control measurements of lower extremities power and the height of rise of the body mass centre in CMJ jumps on the dynamometric platform, were taken every Monday: before training (0), during 4 weeks of training (1-4) and for 2 weeks after it (5-6). Four week training elicited in groups M10, M5, W45 and W45 significant increase of the maximal (except group W45 where it was unimportant) and average power and, decrease of the height of the body mass centre lift in CMJ jump: crucial in groups W45 (-4.7%) and W80 (-4.7%) and not important in M10 (-3.4%). The height of rise of the body mass centre insignificant increase in group M5 (2.1%) after 4 week training. KEY WordS: cycle ergometer training, cMJ, height of jump, power output Linossier et al. [25,26,27], Parry et al. [28], Simoneau et al. [32,33] and Stathisa et al. [35] the sprint training on the cycloergometer elicited the growth of the maximal power and the amount of performed work in the Wingate test – 10 lasting for 90 s maximal efforts and calculated from F-v and P-v characteristics. On the other hand, in work of Fidelus et al. [13] the growth of muscle torque and the power loos during maximal jump on the inclined plane was noticed after 4 week speed training. Changes of lower limb power and height of rise of the body mass centre under the influence of training performed on the cycloergometer are not widely described in references. Only in few of works it is possible to find some significant dependences between the maximal power produced on the cycloergometer and lower extremities power [8,9] and the height of rise of the body mass centre measured in CMJ [38] and SJ jumps [19]. Namely, it might be expected that if the maximal power, calculated from F-v and P-v dependences, grows after the cycloergometer training (Wingate test) than the maximal power measured on the dynamometric platform also should be growing. Original Paper Biol. Sport 2010;27:35-40

The muscle torque per unit volume of the hamstrings on the injured and uninjured sides in patients with ACL reconstruction were compared with participants with no history of knee injury to examine whether a similar mechanism leading to quadriceps weakness exists in the hamstrings of these patients. The study population consisted of 18 and 52 patients ator=6 and 12 months after ACL reconstruction, respectively, and 35 healthy controls. The hamstring volume was measured on MRI. To identify the muscle torque per unit volume, the peak torque of knee flexion was divided by the hamstring volume. Most muscle torque per unit volume indexes were not significantly different between the patients ator=6 months (injured side: 0.133+/-0.03 Nm/cm(3), 60 degrees /s; 0.107+/-0.03 Nm/cm(3), 180 degrees /s; uninjured side: 0.139+/-0.02 Nm/cm(3), 60 degrees /s; 0.107+/-0.02 Nm/cm(3), 180 degrees /s) and controls (0.170+/-0.05 Nm/cm(3), 60 degrees /s; 0.121+/-0.05 Nm/cm(3), 180 degrees /s). However, the muscle torque per unit volume of patients at 12 months in both injured (0.118+/-0.03 Nm/cm(3), 60 degrees /s; 0.092+/-0.02 Nm/cm(3), 180 degrees /s) and uninjured sides (0.120+/-0.03 Nm/cm(3) at 60 degrees /s; 0.094+/-0.02 Nm/cm(3), 180 degrees /s) were significantly lower than those of controls (P0.01). We found no evidence of recruitment disorder in the hamstrings of the patients. The results of this study indicated that the mechanism of muscle weakness of the hamstrings after reconstruction was different from that of the quadriceps, although the precise mechanism remains to be determined.

application/pdf, This study aimed to compare the muscle activities of the lower limb during overground level running (LR) and uphill running (UR) by using a musculoskeletal model. Six male distance runners ran at three running speeds (slow: 3.3 m/s; medium: 4.2 m/s; and high: 5.0 m/s) on a level runway and a slope of 9.1% grade in which force platforms were mounted. A musculoskeletal leg model and optimization were used to estimate the muscle activation and muscle torque from the joint torque of the lower limb calculated by the inverse dynamics approach. At high speed, the activation and muscle torque of the muscle groups surrounding the hip joints, such as the hamstrings and iliopsoas, during the recovery phase were significantly greater during UR than during LR. At all the running speeds, the knee extension torque by the vasti during the support phase was significantly smaller during UR. Further, the hip flexion and knee extension torques by the rectus femoris during UR were significantly greater than those during LR at all the speeds; this would play a role in compensating for the decrease in the knee extension torque by the vasti and in maintaining the trunk in a forward-leaning position. These results revealed that the activation and muscle torque of the hip extensors and flexors were augmented during UR at the high speed.

This study was performed to obtain evidence regarding bilateral hindrance of motor unit (MU) recruitment in the quadriceps femoris (QF) of patients with anterior cruciate ligament (ACL) reconstruction. The subjects included 70 patients who underwent ACL reconstruction and 35 healthy subjects. To identify the muscle torque per unit volume (MTPUV), the peak torque of each velocity of isokinetic performance was divided by muscle volume of the QF measured by a series of cross-sectional images obtained by magnetic resonance imaging scans. Tests revealed that the mean MTPUV of the uninjured (0.113+/-0.03 N m/cm3 at 60 degrees /s, 0.081+/-0.02 N m/cm3 at 180 degrees /s) and injured sides (0.109+/-0.03 N m/cm3 at 60 degrees /s, 0.079+/-0.023 N m/cm3 at 180 degrees /s) were significantly lower than those of the control group (0.144+/-0.05 N m/cm3 at 60 degrees /s, 0.096+/-0.04 N m/cm3 at 180 degrees /s). Previous studies suggested that MU recruitment in the QF of patients with ACL injury was hindered bilaterally. However, the design of their studies could not provide evidence of bilateral hindrance of MU recruitment in the QF. The results of the present study demonstrated that the MTPUV of both injured and uninjured sides of patients were significantly lower than those of the control group.

Although rugby is a popular contact sport and the isokinetic muscle torque assessment has recently found widespread application in the field of sports medicine, little research has examined the factors associated with the performance of game-specific skills directly by using the isokinetic-type rugby scrimmaging machine. This study is designed to (a) measure and observe the differences in the maximum individual pushing forward force produced by scrimmaging in different body postures (3 body heights x 2 foot positions) with a self-developed rugby scrimmaging machine and (b) observe the variations in hip, knee, and ankle angles at different body postures and explore the relationship between these angle values and the individual maximum pushing force. Ten national rugby players were invited to participate in the examination. The experimental equipment included a self-developed rugby scrimmaging machine and a 3-dimensional motion analysis system. Our results showed that the foot positions (parallel and nonparallel foot positions) do not affect the maximum pushing force; however, the maximum pushing force was significantly lower in posture I (36% body height) than in posture II (38%) and posture III (40%). The maximum forward force in posture III (40% body height) was also slightly greater than for the scrum in posture II (38% body height). In addition, it was determined that hip, knee, and ankle angles under parallel feet positioning are factors that are closely negatively related in terms of affecting maximum pushing force in scrimmaging. In cross-feet postures, there was a positive correlation between individual forward force and hip angle of the rear leg. From our results, we can conclude that if the player stands in an appropriate starting position at the early stage of scrimmaging, it will benefit the forward force production.

A number of strength parameters were investigated in a group of subjects with chronic anterior cruciate ligament deficiency; The response of subjects' hamstring muscles to a perturbation on an isokinetic dynamometer was fractionated into the premotor and motor times. Rate of force development in the 75 ms following the perturbation was also measured. The functional ability of the subjects was examined using the Noyes knee rating system. The results showed that the motor time was significantly correlated with the rate of force development and functional ability of the subjects. The ratio of hamstring to quadriceps torque recorded at peak and 30° flexion during isokinetic muscle work at 180°/s was also investigated. No significant relationship was observed between these ratios and functional ability. These findings indicate that factors other than peak hamstring muscle torque may be important to the level of functional ability attained by people with chronic anterior cruciate ligament deficiency.

Foot and ankle structures are the most commonly affected in people with gout. However, the effect of gout on foot and ankle muscle strength is not well understood. The primary aim of this study was to determine whether differences exist in foot and ankle muscle strength for plantarflexion, dorsiflexion, inversion and eversion between people with gout and age- and sex-matched controls. The secondary aim was to determine whether foot and ankle muscle strength was correlated with foot pain and disability.Peak isokinetic concentric muscle torque was measured for ankle plantarflexion, dorsiflexion, eversion and inversion in 20 participants with gout and 20 matched controls at two testing velocities (30°/s and 120°/s) using a Biodex dynamometer. Foot pain and disability was measured using the Manchester Foot Pain and Disability Index (MFPDI).Participants with gout demonstrated reduced muscle strength at both the 30°/s and 120°/s testing velocities for plantarflexion, inversion and eversion (P0.05). People with gout also displayed a reduced plantarflexion-to-dorsiflexion strength ratio at both 30°/s and 120°/s (P0.05). Foot pain and disability was higher in people with gout (P0.0001) and MFPDI scores were inversely correlated with plantarflexion and inversion muscle strength at the 30°/s testing velocity, and plantarflexion, inversion and eversion muscle strength at the 120°/s testing velocity (all P0.05).People with gout have reduced foot and ankle muscle strength and experience greater foot pain and disability compared to controls. Foot and ankle strength reductions are strongly associated with increased foot pain and disability in people with gout.

Aim The purpose of this study was to compare muscle torque during isokinetic knee movements of patients after total knee arthroplasty (TKA) with a similar healthy group. Method 43 patients were examined 3 years after primary total knee arthroplasty with an isokinetic dynamometer (Cybex 340). Torque measurements were evaluated for extension and flexion with 4 different velocities. The results were compared with a group of 43 people without knee disease. Bouth groups consist of 29 women and 14 men. The mean age was also comparable (66.4 vs. 65.8 years). Results A mean peak torque of 65.9 Nm was measured during extension with low velocity (60 degrees /s) in the group of patients with TKA -- 84.3 % of the control group (p = 0.079). At the highest velocity the patients produced 30.2 Nm. This was 72.8 % of the control group (difference statistically significant, p = 0.006). No differences were found in the Extension/Flexion ratio between the two groups. Conclusion The deficites of knee strength in patients after TKA are more distinct in high velocities of motion.

Relationships between physiological parameters and 5-km running performance were examined in 15 male runners (17.3 ± 0.9 years). Running economy (RE) and blood lactate concentration ([BLa]) at 241.2 m/min, VO2max, velocity at VO2max (vVO2max), vertical jump height and muscle power, and isokinetic knee extension strength at 60°/sec and 240°/sec were measured. The participants’ best 5-km race time over the last month of the cross-country season (16.98 ± 0.76 min) was used in the analysis. The data were analyzed using Pearson correlation coefficients. Significant relationships to run time were observed for VO2max (r = -.53), RE (r = .55), and vVO2max (r = -.66), but not [BLa], isokinetic muscle torque, or vertical jump. Identifying the unique strength and power characteristics related to running performance in this age group is warranted.

Introduction: This paper is a literature review on the electromyographic and kinetic strategies used by the central nervous system to control voluntary movement. Such strategies have been identified from carrying out simple and complex movements, with and without direction reversal. Objective: To discuss the set of rules used to modulate the muscle activity patterns and muscle torque generated during voluntary movements involving one and two joints. Electromyographic strategies used to control simple movements involving one or two joints are dealt with first. Kinetic strategies are discussed in terms of the generation and modulation of muscle torque to carry out simple and complex movements. Linear synergy between muscle activity and muscle torque and the correlation of the muscle torque generated between chain-linked joints are then discussed. The role of interactive forces in the control of movements is also discussed. Conclusion: Physical therapy practice requires a theoretical framework based on technical-scientific knowledge to guide it. Motor control theories are powerful tools for this. Such knowledge could be used towards understanding the adaptations and modifications in motor control mechanisms that occur as a result of disorders or disease.

Background: Isokinetic dynamometry allows the measurement of several variables related to muscular performance, many of which are seldom used, while others are redundantly applied to the characterization of muscle function. Objectives: The present study aimed to establish the particular features of muscle function that are captured by the variables currently included in isokinetic assessment and to determine which variables best represent these features in order to achieve a more objective interpretation of muscular performance. Method: This study included 235 male athletes. They performed isokinetic tests of concentric knee flexion and extension of the dominant leg at a velocity of 60º/s. An exploratory factor analysis was performed. Results: The findings demonstrated that isokinetic variables can characterize more than muscle torque production and pointed to the presence of 5 factors that enabled the characterization of muscular performance according to 5 different domains or constructs. Conclusions: The constructs can be described by torque generation capacity; variation of the torque generation capacity along repetitions; movement deceleration capacity; mechanical/physiological factors of torque generation; and acceleration capacity (torque development). Fewer than eight out of sixteen variables are enough to characterize these five constructs. Our results suggest that these variables and these 5 domains may lead to a more systematic and optimized interpretation of isokinetic assessments.

Summary Study aim: The aim of this study was to assess proportion and symmetry between torque in muscles that affect the hip joint in the non-amputated and the amputated limb in persons both engaged in and not engaged in sports. Material and methods: Study participants comprised 12 persons with above-knee leg amputation. The group of participants was divided into two subgroups: persons engaged in sports and physically inactive persons. The strength and the speed capacity of hip joint flexors and hip joint extensors were measured using a Biodex System 4 dynamometer. The measurement was conducted at two angular velocities (60°/s and 120°/s) and during isometric activity of the non-amputated and the amputated limb. Results: Maximal torque of hip joint flexors in the amputated limb of physically active persons constituted 65.3% of the corresponding value in persons without amputation and was higher than in physically inactive persons (55.9%). Similar values were obtained for extensors. The time to reach maximal muscle torque in the amputated limb during the extension of the hip joint at 60°/s equalled 400 ms in physically active persons and 900 ms in physically inactive persons and during flexion, equalled 400 ms and 600 ms, respectively. Conclusions: Physically active persons showed greater dynamics in generating maximal muscle torque, especially during the extension of the hip joint. Physical activity benefits the strength and speed capacity of muscles that affect the hip joint in persons with above-knee amputation, thus decreasing asymmetry and disproportion between limbs.

Objectives To assess the time course of changes in rapid muscle force/torque production capacity and neuromuscular activity of lower limb muscles in response to prolonged (∼2 h) match-play tennis under heat stress. Methods The rates of torque development (RTD) and electromyographic activity (EMG; ie, root mean square) rise were recorded from 0 to 30, –50, –100 and – 200 ms during brief (3–5 s) explosive maximal isometric voluntary contractions (MVC) of the knee extensors (KE) and plantar flexors (PF), along with the peak RTD within the entirety of the torque-time curve. These values were recorded in 12 male tennis players before (prematch) and after (postmatch, 24 and 48 h) match-play in HOT (∼37°C) and COOL (∼22°C) conditions. Results The postmatch core temperature was greater in the HOT (∼39.4°C) vs COOL (∼38.7°C) condition (p

Seventeen patients (15 men and 2 women) with surgically repaired Achilles tendon ruptures had a mobile cast applied for 6 weeks after the operation that allowed free ankle joint motion. A 12-month follow-up study was performed, with measurements of isokinetic muscle torque in a modified Cybex II dynamometer and a dynamic heel-raise test of muscle fatigue. A majority of the patients were weaker on the treated side in both the isokinetic and the heel-raise tests. The isokinetic plantar flexion torque showed larger differences at an angular velocity of 12°/s than at 90°/s. Seven of the patients in the heel-raise test showed considerable differences between the treated and untreated sides, but our analysis could not explain this with any Certainty.

Information on the dynamic properties (joint stiffness, viscosity and limb inertia) of the human knee joint is scarce in the literature, especially for actively contracting knee musculature. A joint driving device was developed to apply small-amplitude random perturbations to the human knee at several flexion angles with the subject maintaining various levels of muscle contraction. It was found that joint stiffness and viscosity increased with muscle contraction substantially, while limb inertia was constant. Stiffness produced by the quadriceps was highest at 30 degrees flexion and decreased with increasing or decreasing flexion angle, while knee flexors produced highest stiffness at 90 degree flexion. When knee flexion was < 60 degrees, stiffness produced by the quadriceps was higher than that of the hamstrings and gastrocnemius at the same level of background muscle torque, while knee flexor muscles produced higher stiffnesses than the quadriceps at 90 degree flexion. Similar but less obvious trends were observed for joint viscosity. Passive joint stiffness at full knee extension was significantly higher than in more flexed positions. Surprisingly, as the knee joint musculature changed from relaxed to contracting at 50% MVC, system damping ratio remained at about 0.2. This outcome potentially simplifies neuromuscular control of the knee joint. In contrast, the natural undamped frequency increased more than twofold, potentially making the knee joint respond more quickly to the central nervous system commands. The approach described here provides us with a potentially valuable tool to quantify in vivo dynamic properties of normal and pathological human knee joints.

In a prospective study 60 patients were randomized to brace and no-brace groups after bone-tendon-bone anterior cruciate ligament reconstruction. The brace group wore a rehabilitation orthosis for 12 weeks postoperatively, while the no-brace group was mobilized immediately, and crutches were discarded 2 weeks postoperatively. The groups were comparable with respect to age, gender, time from injury to surgery, knee score (Lysholm), activity level (Tegner), degree of laxity and isokinetic muscle torque. Although compared with the preoperative situation patients in both groups had significantly improved, there were no differences between the groups 1 and 2 years postoperatively in terms of functional outcome (Lysholm and Tegner scores), stability of the knee or isokinetic muscle torque.