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Russian forms of electrical stimulation became popular to a large extent as a result of the activities of Kots, who claimed force gains of up to 40% in elite athletes as a result of what was then a new form of stimulation. He did not provide details of his published work, nor did he give references. Russian electrical stimulation became popular despite the lack of research in the English-language literature. No studies published in English examined whether the “10/50/10” treatment regimen (10 seconds of stimulation followed by 50 seconds rest, repeated for 10 minutes) advocated by Kots is optimal, and only one study addressed whether maximum muscle torque was produced at an alternating current frequency of 2.5 kHz. The few studies that compared low-frequency monophasic pulsed current and Russian electrical stimulation are inconclusive. This article reviews and provides details of the original studies by Kots and co-workers. The authors contend that these studies laid the foundations for the use of Russian forms of electrical stimulation in physical therapy. The authors conclude that there are data in the Russian-language literature that support the use of Russian electrical stimulation but that some questions remain unanswered.

The accurate measurement of human joint torque is one of the research hotspots in the field of biomechanics. However, due to the complexity of human structure and muscle coordination in the process of movement, it is difficult to measure the torque of human joints in vivo directly. Based on the traditional elbow double-muscle musculoskeletal model, an improved elbow neuromusculoskeletal model is proposed to predict elbow muscle torque in this paper. The number of muscles in the improved model is more complete, and the geometric model is more in line with the physiological structure of the elbow. The simulation results show that the prediction results of the model are more accurate than those of the traditional double-muscle model. Compared with the elbow muscle torque simulated by OpenSim software, the Pearson correlation coefficient of the two shows a very strong correlation. One-way analysis of variance (ANOVA) showed no significant difference, indicating that the improved elbow neuromusculoskeletal model established in this paper can well predict elbow muscle torque.

Background and objective: There are many studies that have examined the differences in isokinetic strength performance differences in athletes; however, observing these angular velocity-dependent differences on surface maps is a very practical and useful application. The aim of this study was to determine the angular velocity-dependent isokinetic knee extensor/flexor muscle strength and jump performance and to compare the test results and 3D torque-angle-velocity surface maps of amateur and professional volleyball players. Materials and methods: We included 25 well-trained male volleyball players (14 professionals and 11 amateurs) with a mean age of 21.8 ± 2.6 years (range 18–27 years) in this cross-sectional study. The dominant knee concentric muscle contractions were analyzed at 300, 120, and 60∘/s angular velocities to determine peak torque (PT), total work (TW), mean power (MP), angle of peak torque (APT), and hamstring-to-quadriceps torque ratio (H:Q). Vertical jump performance was assessed using countermovement jump (CMJ) test. These data were processed using a MATLAB algorithm for constructing the 3D torque-angle-velocity surface maps. Results and conclusions: Significant differences were identified for extensor–flexor PT between PRO and AT at 300 and 120∘/s (p < 0.05). Moreover, there were significant differences between groups for MP and APT at 300 and 120∘/s for TW at all velocities. CMJ test results were significantly different between the groups (p < 0.05). Amateur and professional male volleyball players showed different concentric knee strengths across isokinetic velocities and different eccentric strengths on CMJ test. 3D surface maps can play an important role in the comparative analysis of athletes with different sports backgrounds or in performance analyses when tracking individual development and provide a detailed and understandable perspective in revealing differences. It can also be of help in detection of possible deficits in muscle strength and load range before and after potential injuries.

[Purpose] Changes in the muscle performance of professional motorized athletes using pycnogenol-containing supplements have not been clarified. The purpose of this study was to evaluate the changes in muscle strength and endurance of professional cyclists during 4 weeks of training with the use of PycnoRacerTM. [Participants and Methods] Eight professional cyclists were requested to consume PycnoRacerTM twice/day for 4 weeks. The muscle endurance test consisted of 50 consecutive knee flexion and extension exercises at 180°/sec using an isokinetic torque machine before and after PycnoRacerTM administration. The athletes' body composition, including leg muscle mass, was also measured. [Results] The maximum flexor muscle torque and 41st-50th flexion muscle torque values significantly improved after supplement consumption (average improvement of 8.5%; range, 13.3-67.2%). The leg muscle mass and body composition did not differ significantly between the two conditions. The participants showed an average improvement of 31.8% (range, 0.9-67.8%) in their total work with cycling training. No adverse events were observed. [Conclusion] The use of PycnoRacerTM may improve training, muscle strength, and endurance, but not muscle mass.

Using detailed musculoskeletal models in computer simulations of human movement can provide insights into individual muscle and joint loading; however, these muscle models increase problem dimensionality and require difficult-to-fit parameters. Here, we provide a brief overview of a muscle model alternative, muscle torque generators (MTGs), and highlight how MTG functions have been used by researchers to generate accurate dynamic simulations of optimal sports performance. Multibody dynamic models of a golf drive, track cycling, and wheelchair propulsion were designed and actuated using MTGs. Each MTG was effectively a rotational, single muscle equivalent that contained joint angle/velocity scaling and passive elements to mimic Hill-type muscle model behaviour. Optimal control algorithms were used to predict how each model would execute their respective sports task; these results were compared against experimental data collected from elite athletes. Good agreement between simulated and experimental movement trajectories was observed, with relatively low computational times required for convergence of the MTG-driven multibody simulations.

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.

Spinal cord injury (SCI) results in deleterious skeletal muscle adaptations, such as relevant atrophy and loss of force. In particular, the relevant loss of lower-limb force-generating capacity may limit functional mobility even if neuronal control was sufficient. Currently, methods of assessing maximal force-generating capacity using neuromuscular electrical stimulation (NMES) are limited in individuals who cannot tolerate higher stimulation amplitudes, such as those with residual sensation and those at risk of fracture. In this study, we examined the relationship between NMES amplitude and muscle torque exerted (recruitment curve) in order to determine whether maximal torque output can be characterized by a submaximal marker. Recruitment curves for knee extensors, knee flexors, and ankle plantarflexors were recorded from 30 individuals with motor complete SCI. NMES was delivered starting with an amplitude of 5 mA, and increasing by 5 mA for every subsequent stimulation until either the participant requested to stop the stimulation or the maximum stimulation amplitude (140 mA) was reached. Significant correlations between peak slope of the recruitment curve and peak torque for all muscle groups were found (knee extensors, r = 0.75; p 0.0001; knee flexors, r = 0.68; p 0.0001; ankle plantarflexors, r = 0.91; p 0.0001), indicating that muscles that show greater peak slope of the recruitment curve tend to generate a greater peak torque. This suggests that peak slope, which was achieved at an average stimulation intensity (55.0 mA) that was 43% smaller than that corresponding to peak torque (97.4 mA), may be used as a submaximal marker for characterizing maximal torque output in individuals with SCI.

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.

Purpose: The main objective of this study was to evaluate the level of muscle strength by using isokinetic and isometric measurements—more specifically, the force ratio between the knee flexors and extensors (values of the torques). Methods: An experimental group of elite volleyball players (n = 14) were compared to a control group (n = 14) of healthy non-athletes of comparable ages. Torque measurements were obtained under three concentric conditions (angular velocities of 60 °/s, 180 °/s, and 300 °/s) and one static condition by utilizing the Biodex System 3. Results: In all trials, the volleyball players achieved significantly higher peak torque (PT) values for both the extensors and flexors (p &lt, 0.05) than those of the control group. However, the strength ratio of the flexors and extensors (H/Q) in the experimental group was only 83% of the standard reported in the literature. The most developed and dominating muscles in the knee joints of the volleyball players were the extensors, which accounted for the low strength ratio and dynamic instability of this joint. Conclusion: Based on a proper assessment of the strength ratio of the knee flexors and extensors, properly selected and implemented resistance training can improve the maximum strength and power production and reduce the incidence of injuries in volleyball.

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.

Submitted by RONALDO VALDIR BRIANI (ronaldo.briani@unesp.br) on 2021-05-29T11:31:44Z No. of bitstreams: 1 Tese completa.pdf: 2244578 bytes, checksum: ed7c287afef803e140f136b7f0873e17 (MD5) Rejected by Claudia Adriana Spindola null (claudia@fct.unesp.br), reason: Boa Tarde, Solicitamos que realize correções na submissão seguindo as orientações abaixo: - Segundo a estrutura do texto, após o Abstract e palavras-chave, inclui uma folha com a Lista de Tabelas. Agradecemos a compreensão. Qualquer dúvida entre em contato pelo e-mail bibaqu.fct@unesp.br 18 99760-1512 on 2021-06-01T21:22:29Z (GMT) Submitted by RONALDO VALDIR BRIANI (ronaldo.briani@unesp.br) on 2021-06-02T13:16:53Z No. of bitstreams: 1 Tese completa.pdf: 2712460 bytes, checksum: 25430d06f7030c70ca868e811745e26e (MD5) Approved for entry into archive by Claudia Adriana Spindola null (claudia@fct.unesp.br) on 2021-06-02T13:44:15Z (GMT) No. of bitstreams: 1 briani_rv_dr_prud.pdf: 2712460 bytes, checksum: 25430d06f7030c70ca868e811745e26e (MD5) Made available in DSpace on 2021-06-02T13:44:15Z (GMT). No. of bitstreams: 1 briani_rv_dr_prud.pdf: 2712460 bytes, checksum: 25430d06f7030c70ca868e811745e26e (MD5) Previous issue date: 2021-04-30 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) A dor femoropatelar (DFP) é caracterizada por dor na região anterior do joelho exacerbada por atividades que aumentam a sobrecarga da articulação femoropatelar. Um dos principais focos de estudos em DFP são os músculos extensores de joelho, extensores e abdutores de quadril. Apesar da importância comprovada desses grupamentos musculares na DFP, essa desordem tem característica multifatorial e outros grupos musculares também podem estar comprometidos. Achados de estudos prévios indicam que alterações na funcionalidade dos flexores de joelho e músculos do tronco (flexores laterais, anteriores e extensores) também podem estar associadas com a DFP, embora mais estudos sejam necessários para avançar o entendimento nessa temática. Além disso, o comprometimento da função dos músculos do tronco e flexores de joelho pode estar associado com alterações na mecânica articular durante tarefas funcionais devido à DFP. Para entender melhor a influência da DFP na mecânica articular do tronco e membro inferior, reduzindo limitações causadas pelo carácter intermitente da DFP e o desenho transversal da maioria dos estudos, investigar a influência da exacerbação da DFP nessas variáveis pode ser uma alternativa interessante. Nesse contexto, seis estudos originais que compõem esta tese foram realizados com o objetivo geral de investigar a relação da DFP com os músculos do tronco e flexores de joelho e a influência da exacerbação da DFP na mecânica articular do tronco e membro inferior. De forma geral, os achados desses estudos indicaram comprometimento na função muscular dos flexores de joelho e dos músculos do tronco, o que está relacionado com a dor ou função objetiva de indivíduos com DFP. Além disso, foram encontradas mudanças na mecânica articular do joelho e na coordenação de tronco durante tarefas funcionais após a exacerbação da DFP. Em conjunto, esses achados contribuem no entendimento da relação dos músculos do tronco e flexores de joelho com a DFP e como a sua exacerbação influencia a mecânica articular. Patellofemoral pain (PFP) is characterized by diffuse anterior knee pain exacerbated by activities that increase the load in the patellofemoral joint. One of the main focus of PFP research has been the knee extensors, hip abductors and extensors. Despite the evidenced importance of these muscle groups to PFP, this disorder has a multifactorial characteristic and other muscle groups may also be compromised. Findings from previous studies indicate that changes in the muscle capacity of the knee flexors and trunk muscles (lateral, anterior and extensor flexors) may also be associated with PFP, although further studies are needed to further understand this topic. In addition, impaired function of the trunk and knee flexor muscles may be associated with changes in joint mechanics during functional tasks due to PFP. To better understand the influence of PFP on trunk and lower limb mechanics, overcoming limitations caused by the intermittent nature of PFP and the cross-sectional design of most studies, investigating the influence of PFP exacerbation on these variables can be an interesting alternative. In this context, six original studies that compose this thesis were carried out with the general objective of investigating the relationship of PFP with trunk and knee flexor muscles and the influence of PFP exacerbation on trunk and lower limb mechanics. Overall, the findings of these studies indicated impairments in the muscle function of the knee flexors and trunk muscles, which were related to pain or objective function of individuals with PFP. In addition, changes in knee joint mechanics and trunk coordination were found during functional tasks after the exacerbation of DFP. Put together, these findings contribute to the understanding of the relationship between trunk and knee flexor muscles with PFP and how the exacerbation of PFP influences joint mechanics. FAPESP: 17/20483-7 CAPES: 001

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.

The condition of active assistance is the basic design criteria of target assistance torque profile. Based on the human-exoskeleton interaction model, the condition of active assistance was derived first. And then, some biomechanical simulation experiments based on OpenSim were carried out to demonstrate the the condition of active assistance. The condition of active assistance for exoskeleton robot is that the target assistance torque and the human joint muscle torque should be in a same direction and the assistance ratio should be greater than 0 and less than 1.

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...

Nowadays, exoskeletons are widely used as assistive tools during gait rehabilitation, implementing strategies such as gravity compensation and metabolic cost reduction. However, these devices often require the use of motors and controllers. Our research is driven by the need for a simple, inexpensive and customizable device, a passive exotendon able to provide a desired torque profile to multiple joints. In a simulation model study, we asked whether it was possible to use diagonal tension elements, which act mathematically as basis functions, in order to reproduce the torque field generated by a healthy person during walking. This would allow us to create a wearable exotendon system made of passive elastic elements able to deliver this torque field to the lower extremity of the patient during gait rehabilitation. Our results showed that it is indeed possible to create a passive torque field from elastic elements that approximates the muscular torque demand for the walking cycle. This represents a starting point for the design of a passive exotendon capable of providing assistive torques to patients with motor deficits, thus reducing the metabolic cost of walking.

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.

Instrument-assisted soft tissue mobilization (IASTM) is a new technique that has been known to be effective in reducing muscle tightness in athletics. However, little is known about its effect on the range of motion, muscle power, and torque compared to manual stretching among non-athletics. Thus, the study was aimed to compare the effectiveness between IASTM and manual stretching in improving hip flexion active range of motion (ROM), muscle torque and power on hamstring muscle complex (HMC) tightness in one session.Twenty-three young male college students with unilateral hamstring tightness measured via straight leg raising (SLR) test (65°) were randomly assigned to one of two groups. Twelve participants received the application of IASTM (group 1), and eleven received manual stretching (group 2). Hip flexion active ROM was measured via goniometer, the torquepower of the hamstring muscle were measured using Humac isokinetic dynamometer, before and after both interventions. (ISRCTN17693345).There was no significant difference in the improvement of hip flexion active ROM (69.6 ± 6.6 vs 72.5 ± 7.9, p = .34), HMC torque (63.7 ± 14.5 vs 53.2 ± 16.3, p = .14), and HMC power (47.8 ± 11.8 vs 40.9 ± 16.3, p = .34) between group 1 and group 2 respectively. When a comparison was made within each group, significant improvements in hip active flexion ROM was found in both groups (p's .001), and HMC power was significantly improved in group 1 (p = .04) but not in group 2.The current study findings demonstrate that IASTM was as effective as manual stretching in improving hip flexion active ROM, muscle torque and power among non-athletic people with HMC tightness.

Bioelectrical impedance spectroscopy (BIS) can assess intracellular water (ICW) and total water (TW) in limbs. This study aimed to examine whether BIS can explain a part of the inter-individual variation of the muscle size-strength relationship in older adults. We analyzed the data of 79 participants aged 64-86 years. The maximal voluntary isometric torques of dorsiflexion and plantar flexion on the right side were measured. The anterior and posterior muscle thickness (MT) in the right lower leg was assessed using ultrasonography. The length of the right lower leg (L) was measured, and the ICW-to-TW ratio (ICW/TW) in the right lower leg was obtained using BIS. The MT was multiplied by L to represent an index of muscle volume (MV). Correlation and stepwise regression analyses were performed. The anterior and posterior MT × L significantly and positively correlated with the muscle torque of dorsiflexion and plantar flexion (r = 0.710 and 0.649, respectively, P 0.001). In the stepwise regression analyses, ICW/TW was selected as a significant predictor of muscle torque independent of MT × L (P 0.05) for both dorsiflexion and plantar flexion. Electrical parameters of BIS (membrane capacitance, characteristics frequency, and phase angle) in the lower leg also significantly correlated with muscle torques. In addition, the skeletal muscle mass index (appendicular lean mass/height

Objectives Knee muscle groups contribute to proper and safe static and dynamic standing posture stability. The impact of isokinetic knee muscle torque at various angular velocities on standing posture stability is poorly understood. We investigated the influence of isokinetic knee muscle torque at different angular velocities on standing posture stability. Design Cross-sectional study. Setting King Saud University Campus labs. Method The study population was a convenience sample of 30 healthy volunteer college students with a mean age of 20±2 years. Isokinetic concentric peak torque (PT) of knee extensor (Q) and flexor (H) muscle groups as well as the flexor to extensor (H:Q) ratio at three different angular velocities: (60, 180, and 300°/s) were measured, respectively. The postural stability was also measured in both static and dynamic components. The Pearson correlation coefficient was used to examine the association between the different isokinetic components and postural stability (both static and dynamic). Results The PT of Q and H muscle groups and the H:Q ratio at the 3 different angular velocities were significantly associated with static standing balance with eye open on a firm surface (p Conclusions The PT of both Q and H muscle groups at different angular velocities are associated with maintenance of standing static balance. PT of Q only is significantly associated with control of dynamic standing balance in the lower angular velocities.

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).

Study Design A controlled laboratory study, with a single-blind, block-randomization crossover design. Objectives To compare the electrically elicited knee extensor torque produced by 3 clinically available waveforms: 2500-Hz burst-modulated alternating current (BMAC), 1000-Hz BMAC, and 1000-Hz burst-modulated biphasic square-wave pulsed current (BMBPC). Background Neuromuscular electrical stimulation (NMES) is the therapeutic use of electrical current to strengthen muscle. Muscle torque produced by NMES is limited by discomfort. Methods The knee extensor maximal volitional isometric torque (KEMVIT) of 33 able-bodied participants (18 female) was measured and used to normalize the electrically elicited knee extensor torque to produce a percent of KEMVIT (%KEMVIT). Electrically elicited isometric knee extensor torque was measured in response to each of the waveforms at the participants' maximum tolerance. Results The average maximum tolerated stimulation produced 32.0 ± 16.7 %KEMVIT with 2500-Hz BMAC, 38.2 ± 18.4 %KEMVIT with 1000-Hz BMAC, and 42.2 ± 17.1 %KEMVIT with 1000-Hz BMBPC. Tukey honest significant difference (HSD) post hoc testing revealed a statistically significant difference between 2500-Hz BMAC and 1000-Hz BMAC (P = .046), and between 2500-Hz BMAC and 1000-Hz BMBPC (P.001). No statistically significant difference was found between 1000-Hz BMAC and 1000-Hz BMBPC (P = .267). Conclusion For eliciting maximum knee extensor muscle torque, 1000-Hz BMBPC and 1000-Hz BMAC were similarly effective, and 2500-Hz BMAC was less effective. J Orthop Sports Phys Ther 2018;48(3):217-224. Epub 19 Dec 2017. doi:10.2519/jospt.2018.7601.

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.

Background Therapeutic management of the upper extremity (UE) function of people with spinal muscular atrophy (SMA) requires sensitive and objective assessment. Therefore, we aimed to measure physiologic UE function of SMA patients with different functional abilities and evaluate the relation between these physiologic measures and functional UE scales. Methods 12 male and 5 female SMA patients (mean age 42 years; range 6–62 years) participated in this explorative study. Concerning the physiologic level, the maximal muscle torque, the maximal and normalized surface electromyography (sEMG) amplitudes, and the maximal passive and active joint angles were measured. Concerning the activity level, the Performance of the Upper Limb (PUL) scale was used, and hand function was examined using the Nine-Hole Peg Test and the Timed Test of In-Hand Manipulation (TIHM). Results Outcome measures that significantly related to the functional ability were: the PUL score (all dimensions); the finger to palm task of the Timed TIHM; biceps, triceps, and forearm extensor strength; and the active range of motion of shoulder abduction, shoulder flexion, and wrist extension. In addition, the following physiologic variables were related to the activity level (PUL score): hand function (the Nine-Hole Peg Test; Rs = − 0.61), the Timed TIHM (Rs = − 0.53), the maximal muscle torque (Rs = 0.74), the maximal sEMG amplitude (Rs = 0.79), and the maximal active joint angle (Rs = 0.88). Conclusions Muscle functions in SMA patients are already affected before activity limitations are noticeable. Consequently, monitoring the maximal muscle strength and the normalized muscle activity during task performance could play a role in the early detection of UE limitations. The mechanism behind the loss of arm activities due to SMA is primarily caused by decreasing muscle capacity, which influences the ability to move an arm actively. In clinical practices, these dimensions should be considered separately when monitoring disease progression in order to better evaluate the need for interventions.

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.

Objectives: Determine the effects of varying frequency, phase duration, and interphase interval (IPI) of symmetrical, biphasic pulsed current (SBPC) on quadriceps femoris muscle torque production, ...

To test the hypothesis that a system’s metabolic rate and the complexity of fluctuations in the output of that system are related, thirteen healthy participants performed intermittent isometric knee extensor contractions at intensities where a rise in metabolic rate would (40% maximal voluntary contraction, MVC) and would not (20% MVC) be expected. The contractions had a 60% duty factor (6 sec contraction, 4 sec rest) and were performed until task failure or for 30 min, whichever occurred sooner. 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. Muscle metabolic rate was determined using near‐infrared spectroscopy. At 40% MVC, task failure occurred after (mean ± SD) 11.5 ± 5.2 min, whereas all participants completed 30 min of contractions at 20% MVC. Muscle metabolic rate increased significantly after 2 min at 40% MVC (2.70 ± 1.48 to 4.04 ± 1.23 %·s‐1, P

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.

Analyses of human action forces is a standard function of current digital human models. However, research has been indicating that this feature needs to be improved as it lacks accuracy. Muscle-torque based modeling can be used to calculate action forces. Because it is not efficient to measure torques in all spatial directions, different calculating approaches have been developed. The question is which one is the best to calculate action forces? In this paper, we will therefor explain four different calculations - a spherical, linear, independent and fluid approach. To compare their quality, a study based on 366 measurements of maximum torques has been conducted. Results show that the spherical approach predicts maximum muscle torques to about 1.7% accuracy. The fluid approach increases the accuracy significantly (R2 0.9), but needs more input data. Hence, a mix using both approaches is proposed as the best solution to calculate action forces in digital human models.

The aim of this study was to evaluate the effect of long-term running training on muscle strength of men aged 50 and above. The study involved two groups of men aged 50 and above: physically active (E, n = 34) and inactive (NE, n = 20). Body composition was assessed with the electrical bioimpedance method. The isometric maximum voluntary contraction (MVC) was the main measurement. The value of muscle torque achieved by a group of synergists (operating in the given joint) during a short isometric contraction was evaluated. Ten groups of flexor and extensor muscles of the elbow, shoulder, hip, knee, and torso joints were measured. In addition, a 3 s measurement of grip strength of the right (F r ) and left (F l ) hand was taken using a hand dynamometer. The obtained values enabled to calculate the symmetry index (SI). Men who had been running regularly were characterized by a significantly lower strength level ( p < .05). Results in the NE group were determined to a great extent by significantly different body weights ( p < .001) and a significantly higher body fat mass (FAT) content ( p < .001). SI was statistically higher in the reference group ( p < .05). Long-distance run training reduces FAT while maintaining a high level of muscle strength. These studies indirectly confirm the effect of strengthening slow-twitch motor units in men aged 50 (Doherty & Brown 1993; Kanda & Hashizume 1989). In addition, stimulating the body through physical effort helps it also to maintain a high level of strength symmetry, which is a preventive factor in reducing the number of injuries.

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.

An experiment with 52 participants investigated the relationship between movement time of the leg/foot for seated persons when moving in the transverse and sagittal planes. Four amplitudes of movement and 11 values of Fitts' Index of Difficulty (ID) were used to determine conditions under which ballistic movements could be made along with the need for visual control at higher ID values. Vision of the foot was available in all movements. As with arm movements (Gan and Hoffmann, 1988) there was a critical ID value below which it was possible to use ballistic movements and where movement times were approximately linear with the square-root of movement amplitudes. Above these ID values, Fitts' law applied, with gradients dependent on the amplitude of movement, suggesting that the muscle torque applied to the leg varied with movement amplitude. The critical ID varied with the amplitude of movement as previously found for arm movements. Relevance to industry There is increasing use of the foot/leg for input to various controlling devices. Consequently it is necessary to have detailed information on the capacity of the leg/foot system to provide accurate input to a machine via a control pedal or other device. The present research provides such information over a wide range of control sizes and spacings.

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.

Research background and hypothesis. There is much research information about the relationship between the knee joint angle and the quadriceps muscle torque (Mohamed et al., 2002), but still we lack evidence about the relationship between ankle angle and calf muscle torque. Research aim. The purpose of this research was to establish the dependence of maximal voluntary contraction (MVC) and electrical stimulation (ES)-evoked torque and calf muscle electrical activity (EMG) on different ankle plantar and dorsal fl exion angles. We hypothesized that the calf muscle MVC and ES-evoked torque as well as muscle EMG amplitude would increase with increasing muscle length (i. . increasing ankle angle). Research methods. The subjects in the research were ten non-trained men. Calf plantar and dorsal fl exors muscle ES and MVC torque were tested at eight different ankle angles (–25 o ; –15 o ; –5 o ; 0 o ; 15 o ; 25 o ; 35 o ; 45 o ) which were chosen in randomized sequence. The tibialis anterior, soleus, gastrocnemius lateralis and medialis muscle EMG were measured during muscle MVC. Research results. The results showed that the highest ES-evoked and MVC developed torque of plantar fl exion muscles was at –25° ankle angle (149.1 ± 31.6 N·m and 207.8 ± 38.1 N·m, respectively), while the highest dorsal fl exion MVC muscle torque was at 25° ankle angle (47.2 ± 8.1 N·m). However, dorsal fl exion muscle MVC torque increased with the muscle length only until 25° ankle angle. Discussion and conclusions. Plantar flexion muscle electrical stimulation evoked and plantar / dorsal fl exion muscle maximal voluntary contraction torques are highest at that ankle angle where muscle length is the longest. Keywords: maximal voluntary contraction, electrical stimulation, EMG.

The torque-sharing strategies between synergistic muscles may have important functional consequences. This study involved two experiments. The first experiment ( n = 22) aimed 1) to determine the relationship between the distribution of activation and the distribution of torque-generating capacity among the heads of the hamstring, and 2) to describe individual torque-sharing strategies and to determine whether these strategies are similar between legs. The second experiment ( n = 35) aimed to determine whether the distribution of activation between the muscle heads affects endurance performance during a sustained submaximal knee flexion task. Surface electromyography (EMG) was recorded from biceps femoris (BF), semimembranosus (SM), and semitendinosus (ST) during submaximal isometric knee flexions. Torque-generating capacity was estimated by measuring muscle volume, fascicle length, pennation angle, and moment arm. The product of the normalized EMG amplitude and the torque-generating capacity was used as an index of muscle torque. The distributions of muscle activation and of torque-generating capacity were not correlated significantly (all P > 0.18). Thus, there was a torque imbalance between the muscle heads (ST torque > BF and SM torque; P < 0.001), the magnitude of which varied greatly between participants. A significant negative correlation was observed between the imbalance of activation across the hamstring muscles and the time to exhaustion ( P < 0.001); i.e., the larger the imbalance of activation across muscles, the lower the muscle endurance performance. Torque-sharing strategies between the heads of the hamstrings are individual specific and related to muscle endurance performance. Whether these individual strategies play a role in hamstring injury remains to be determined. NEW & NOTEWORTHY The distribution of activation among the heads of the hamstring is not related to the distribution of torque-generating capacity. The torque-sharing strategies within hamstring muscles vary greatly between individuals but are similar between legs. Hamstring coordination affects endurance performance; i.e., the larger the imbalance of activation across the muscle heads, the lower the muscle endurance.

Inferring a device wearer’s intention is important for supporting devices that exert force, dexterity and sustainability. In this research, we considered a simple ON and OFF function. If one can discriminate whether an order to move a specific muscle is voluntary or involuntary when the command reaches the periphery, estimating the direction in which the supporting device assists the movement is easy. Therefore, in this study, we measured voluntary biceps brachii muscle contraction in response to a visual stimulus, with various stimulus intensities. We found that the preparation start time and the lifting start time were earlier during the condition (“right directional arrow” and “left directional arrow”) where there was high confidence in the choice to execute a forearm lift, among other available stimuli. In contrast, the center frequency of the biceps brachii muscles, at the time of preparing the lifting motion, tended to be higher. Finally, by using an algorithm to infer movement intention, it was possible to identify if the next movement comprised flexion or extension, before muscle torque generation.

OBJECTIVE: After spinal cord injury (SCI), hybrid stimulation patterns that interpose paired-pulse doublets over a constant-frequency background may enhance the metabolic “work” (muscle torque) performed by paralyzed muscle. This study examined the effect of background stimulation frequency on the torque contribution of the doublet before and after fatigue. DESIGN: Cross-sectional study. SETTING: Research laboratory in an academic medical center. PARTICIPANTS: Five men with chronic sensory and motor-complete SCI and ten non-SCI controls (6 males, 4 females). SCI subjects were recruited from a long-term study of unilateral plantar-flexor training; both limbs were tested for the present study. INTERVENTIONS: Subjects underwent plantar flexor stimulation at 5, 7, 9, and 12 Hz. The four background frequencies were overlaid with 6 ms doublets delivered at the start, middle, or at both the start and middle of each train. The 5 Hz and 12 Hz frequencies were analyzed after fatigue. OUTCOME MEASURES: Mean torque, peak torque, torque fusion index, doublet torque. RESULTS: Trains with doublets at both the start and middle yielded the most consistent enhancement of torque (all P

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.

Introduction: In this investigation we aimed to deter- mine 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. Methods: 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. Results: Activity before I/R resulted in 73.2% less mus- cle 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. Conclusions: Activity protects against long- term muscle damage, but not short-term neural injury or excita- tion-contraction uncoupling. Continued activity neither acceler- ates nor hinders the rate of functional recovery. Muscle Nerve 52: 640-648, 2015 Extremity injuries are highly prevalent in both mili- tary 1 and civilian 2 trauma, and they often involve skeletal muscle. 3 In many cases, prolonged blood flow disruption due to concomitant vascular dam- age and/or acute compartment syndrome induces tissue ischemia, and subsequent surgical repair pro- motes reperfusion of the tissue. 4 Tissue reperfusion is necessary for limb salvage, although free radicals generated during this process further injure vascu- lar, neural, and muscular structures (i.e., ischemia/ reperfusion (I/R) injury 5-7 ). The underlying molec- ular mechanisms of I/R injury are fairly well under- stood, and a number of protective agents 8-10 and

The aim of this study is to compare values of force-velocity and functional walking capacity in elderly patients with intermittent claudication with respect to the control group.The study involved 135 individuals: 85-peripheral arterial disease (PAD) group diagnosed with stage II chronic lower limb ischemia, according to Fontaine's classification, and 50-control group. The studies included an assessment of walking capacity using a six-minute walk test (6MWT) and measurement of force-velocity parameters (peak torque-PTQ, total work-TW, average power-AVGP) of the lower limbs obtained by means of a functional dynamometry under isokinetic conditions.The peripheral arterial disease group is characterized by significantly lower values of force-velocity parameters compared to the control group (p0.005). Walking capacity in this group is significantly reduced due to significant differences in the distance covered (p0.0001), walking speed (p0.01), and its intensity (p0.01). Further, a positive correlation was found between the maximum distance specified in the six-minute walk test and lower limb muscle strength in the isokinetic test.Mean values of all force-velocity parameters and walk distance were significantly higher in the control group than in the peripheral arterial disease group. In the PAD group, in both men and women, the value of the agonist/antagonist ratio of both lower limbs are lower in men and women comparing to the control group. A rehabilitation program for patients with intermittent claudication must consider exercises improving strength, exercise capacity, and endurance in patients with PAD.