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INTRODUÇÃO: Dinamômetro isocinético é um equipamento eletrônico e mecânico, capaz de medir o torque gerado por um determinado segmento, bem como a potência e estimar fadiga, observando-se a variação do torque ao longo tempo. Este dispositivo também controla a velocidade do movimento angular, seja ele gerado por uma contração excêntrica ou concêntrica. Este tipo de equipamento tem sido utilizado tanto para avaliação como para treinamento de força. OBJETIVO: Verificar o efeito do treinamento de força, realizado exclusivamente no dinamômetro isocinético, na capacidade de gerar torque isométrico. MÉTODO: 2 homens, sedentários, saudáveis com idade de 23 e 24 anos realizaram 16 sessões de treinamento de força (sempre em esforço máximo e no modo concêntrico utilizando-se um dinamômetro isocinético) para os músculos flexores da articulação do cotovelo do membro dominante. As sessões foram compostas por um treinamento de quatro séries de oito repetições em uma amplitude de movimento de 130º, com velocidade fixada em 45º/s. As avaliações de contração isométrica voluntária máxima (CIVM) a 90º de flexão da articulação do cotovelo foram realizadas na primeira, oitava e décima sexta sessão. Espessura dos músculos flexores da articulação do cotovelo também foi medida, com ultrassonografia, nas mesmas sessões em que o torque máximo isométrico foi medido. RESULTADOS: Não houve diferença significativa no ganho de torque tam pouco na espessura muscular, ao final do treinamento. CONCLUSÃO: Treinamento de força, exclusivamente realizado no modo concêntrico no dinamômetro isocinético não provocou aumento da capacidade de gerar força isométrica, tam pouco aumento da espessura muscular.

Context: The Y Balance Test was developed as a test of dynamic postural control and has been shown to be predictive of lower-extremity injury. However, the relationship between hip strength and performance on the Y Balance Test has not been fully elucidated. Objective: The goal of this study was to identify the relationship between components of isometric hip strength and the Y Balance Test, to provide clinicians better guidance as to specific areas of muscle performance to address in the event of poor performance on the Y Balance Test. Design: Laboratory study. Setting: Biomechanics laboratory. Participants: A total of 73 healthy participants (40 males and 33 females) volunteered for this study. Intervention: None. Main Outcome Measures: Participants completed the Y Balance Test on the right leg. The authors then measured peak isometric torque in hip external rotation, abduction, and extension. Correlations were calculated between torque measurements, normalized for mass and Y Balance Test performance. Significant relationships were used in linear regression models to determine which variables were predictive of the Y Balance Test performance. Results: The authors found significant positive correlations between Y Balance Test performance and hip abduction strength. They also found correlations between the Y Balance Test and hip extension and external rotation strengths. Linear regression analysis showed hip abduction to be the only significant predictor of Y Balance performance. Conclusions: The authors found the strongest association between the Y Balance Test and hip abduction strength. They also showed smaller but significant associations with hip extension and external rotation strength. When entered into a linear regression analysis, hip abduction strength was the only significant predictor of Y Balance performance. Using this information, practitioners should look to hip abduction strength when patients exhibit deficits in the Y Balance Test.

Background Patellofemoral pain is common in physically active adults. Females with patellofemoral pain have been shown to have posterolateral hip muscle weakness, but there is a paucity of research examining hip muscle strength in males with patellofemoral pain. Hypothesis/Purpose The purpose of this study was to examine posterolateral hip muscle strength in males with patellofemoral pain compared to asymptomatic males. It was hypothesized that males with patellofemoral pain would have decreased strength of the hip extensor, hip external rotator, and hip abductor muscles compared to healthy, asymptomatic males. Study Design Descriptive, cross-sectional. Methods Thirty-six adult males with patellofemoral pain and 36 pain-free males participated in the study. The patellofemoral pain group were required to have retropatellar pain reproduced by activities that loaded the patellofemoral joint (squatting, descending stairs, etc.). Peak isometric torque of the hip extensors, hip external rotators, and hip abductors was measured with an instrumented dynamometer. Torque was normalized by body mass and height. Between-group differences were analyzed with parametric or non-parametric tests, as appropriate. The level of significance was adjusted for multiple comparisons. Results Hip extensor torque was significantly reduced in the patellofemoral pain group compared to the control group (p = .0165). No differences were found between groups for the hip external rotators or hip abductors (p > .0167). Conclusion Males with patellofemoral pain appear to have weakness of the hip extensors, but unlike females with patellofemoral pain, they do not appear to have weakness of the hip abductors or hip external rotators. The findings of this study suggest that muscle strength factors associated with patellofemoral pain in males may be different from muscle strength factors in females. Clinicians examining and designing plans of care for male patients with patellofemoral pain should consider that the hip abductors and hip external rotators may not be weak in men with this condition. Level of evidence Level 3.

Chu, E, Kim, Y-S, Hill, G, Kim, YH, Kim, CK, and Shim, JK. Wrist resistance training improves motor control and strength. J Strength Cond Res 32(4): 962-969, 2018-The aim of this study was to investigate the effects of a 6-week direction-specific resistance training program on isometric torque control and isokinetic torque strength of the wrist joint. Nineteen subjects were randomly assigned to either the wrist training group (n = 9) or the control group (n = 10). The training group performed wrist exercises in 6 directions (flexion, extension, pronation, supination, radial deviation, and ulnar deviation), whereas the control group did not. Data were collected on the isometric torque control, 1-repetition maximum (1RM) strength, and isokinetic maximum torque (angular velocity of 60° per second wrist movements) before and after 6 weeks of resistance training and at 2-week intervals during training. The training group showed significant decreases in isometric torque control error in all 6 directions after 2 weeks of resistance training, whereas the control group did not show significant increase or decrease. After 4 weeks of training, the training group showed significant increases in maximum strength in all 6 directions as assessed by 1RM strength and isokinetic strength tests, whereas the control group did not show any statistically significant changes. This study shows that motor control significantly improves within the first 2 weeks of resistance training, whereas the wrist strength significantly improves within the first 4 weeks of resistance training. Based on the findings of this study, coaches and trainers should consider wrist resistance training to improve athletes' muscular strength and control of the wrist muscles.

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.

The objectives of this research were to: (1) investigate the effects of handwheel height and angle of a valve on the muscle loading of shoulder, neck, and back muscles; and (2) identify a handwheel height and angle that best distributes the load of torque exertions to different muscles. Fifteen healthy male participants were recruited for this study. The handwheel heights included knee, elbow, shoulder, and overhead levels. The handwheel angles included 0°, 45°, and 90°. At each height-angle combination, participants performed an isometric torque exertion on a handwheel. During each trial, the maximum electromyography (EMG) activities were measured from the right and left anterior deltoids, trapezii, latissimi dorsi, and erector spinae muscles. EMG data were normalized and reported as percentages of reference contractions (RC). A two factor split-plot analysis of variance (ANOVA) and Tukey multiple pairwise comparison tests were performed to determine the significant effects. Results show that a handwheel at overhead 45°, which allows the greatest torque production, is associated with a concentrated load on the right anterior deltoid (94.1 %RC). At elbow level, participants were exposed to low loads on the shoulder and neck muscles, but that was compensated with higher loads on the back muscles. Based on the EMG results, the best handwheel height and angle appeared to be at shoulder 0°. At this height and angle, seven of the eight muscles were working at or close to their lowest EMG activities, while also allowing the production of relatively large torques (65.2 Nm).

Introduction Volumetric muscle loss (VML) occurs following significant traumatic injury or surgical removal of skeletal muscle, resulting in nonrecoverable loss of tissue and long-term dysfunction. Perhaps less recognized is that VML injuries inherently disrupt the neuromuscular unit, resulting in fiber denervation and presumptive motor unit rearrangement, expansion, and/or loss. To characterize neural dysfunction we quantified motoneuron axotomy, in efforts to understand how this relates to the temporal coordination of neuromuscular and morphological alterations due to injury. Methods In an established rat tibialis anterior (TA) VML injury model, we examined the motoneuron, skeletal muscle, and maximal isometric torque at 3, 7, 14, and 21 days postinjury. Results Significant axotomy of 57-79% of all TA muscle motoneurons was observed through 21 days postinjury, which was coupled with a 45-90% TA maximal torque deficit. Discussion A ∼20% partial ablation of the TA muscle causes disproportionate damage across the motor unit acutely postinjury. Muscle Nerve 57: 799-807, 2018.

The purpose of this study was to compare the benefits and possible problems of 4 weeks stretching when taken to the point of pain (POP) and to the point of discomfort (POD). Twenty-six physically active women (20 ± 1.1 years) took part in group-based stretching classes of the hamstring muscles, 4 times per week for 4 weeks, one group one stretching to POD, the other to POP. Passive stiffness, joint range of motion (ROM), maximal isometric torque and concentric knee flexion torque, were measured before training and 2 days after the last training session. Hip flexion ROM increased by 14.1° (10.1°–18.1°) and 19.8° (15.1°–24.5°) and sit-and-reach by 7.6 (5.2–10.0) cm and 7.5 (5.0–10.0) cm for POD and POP, respectively (Mean and 95% CI; p

Objective: To analyze the effect of maximal voluntary isometric contractions and of electroestimulation on isometric torque and muscle activation of the brachii triceps in physically active adult males. Methods: Nineteen men underwent isometric force tests as pre-test, through 10-second long maximal voluntary isometric contractions and conditioning activities randomized: isometric contraction during 7, 10 and 12 seconds and electric stimulation in 70 and 120 Hz for 10 seconds each. After the conditioning activities, two voluntary isometric contractions were performed for 10 seconds with interval of 4 and 8 minutes, respectively. The muscle electrical activity of brachii triceps (medial and lateral portion’s) was measured. Results: It was not verified effect in any conditions to maximal or mean torque (P>0.05), likewise to muscle electrical activity of brachii triceps (P>0.05). Conclusion: The interval adopted among the conditioning activities and the isometric force test was not enough to induce the isometric torque improvement.

Introduction Despite assumptions, there is an absence of research on acute fatigue responses to high- and low-load and advanced technique resistance exercise. Methods Trained males (n = 8; age 27.2 ± 7.4 years, height 180.0 ± 6.6 cm, weight: 86.6 ± 10.3 kg) were assessed for decrement in maximal voluntary isometric torque (MVIT) and perceived effort and discomfort after heavier load (HL; 80% MVIT), lighter load (LL; 30% MVIT), forced repetition (FR), and breakdown set (BD) training protocols. Results Analyses revealed a significant reduction in MVIT (P 0.05). Discussion Fatigue as a decrement in force production appears to follow a more complex relationship than simply 100% minus the force requirements of the task relative to a maximal voluntary contraction. Muscle Nerve 56: E141–E146, 2017

Purpose: The aim of the study was to assess the usefulness of isometric torque (IT) and peak torque (PT) of the hamstring to quadriceps muscles ratio (H/Q ratio) in monitoring the effectiveness of physiotherapy (PH) in males after ACLR. Hypothesis: The H/Q ratio is a diagnostic tool for monitoring of the effectiveness of the 6- month PH after ACLR. Methods: Twenty males 6 months after ACLR (ACLR group) and 20 male controls underwent IT and PT (60°/s and 180°/s) bilateral measurements of H and Q muscles. The IT and PT were normalized to body mass, and expressed as relative IT (RIT) and relative PT (RPT). The RIT and RPT H/Q ratios, and Limb Symmetry Index (LSI) were calculated. Results: In the ACLR group, the RIT for the H and Q, the RIT for the H/Q ratio and most of the RPT, as well as the H/Q ratio, ROM and LSI values of the operated knee, were not significantly different (NSD) than those of the non-operated side (NOS) or the control group. The between-group comparison of the H/Q ratio for RIT and RPT weren’t NSD. The isokinetic test at 180°/s showed lower RPT, H/Q ratio and LSI values for the Q muscle than those of the NOS (p = 0.042, p = 0.001). Conclusions: The H/Q ratio, in combination with the RIT, RPT and LSI, is a useful diagnostic tool for monitoring the effectiveness of 6-month PH after ACLR. Restoring the correct H/Q ratio can reduce the risk factor for ACL graft rupture.

Context: Myofascial self-release is performed using a roller to exert pressure on the soft tissues and to promote effects similar to those of traditional massage. However, there is no standardization regarding its application, mainly in relation to time. Objective: To evaluate the effects of myofascial self-release with a rigid roller on range of motion (ROM), pressure pain threshold (PPT), and hamstring strength in asymptomatic individuals following 2 different times of intervention. Design: Randomized, controlled, blind, clinical trial comparing preintervention and immediately postintervention within 2 groups. Setting: Institutional physiotherapy clinic. Participants: A total of 40 university students (18–30 y), who had no symptoms, participated. Intervention: Foam roller for 30 seconds and 2 minutes for group 2. Main Outcome Measures: Hamstring PPT, knee-extension ROM, and peak knee-flexion torque measured before and immediately after the intervention. Results: Both groups experienced a statistically significant increase in ROM compared with baseline (30 s and 2 min for group 2 P Conclusions: Hamstring myofascial self-release using a roller for 30 seconds or 2 minutes produced an increase in ROM in healthy individuals. PPT and peak knee-flexion isometric torque showed no effects.

Made available in DSpace on 2018-12-11T17:38:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-10-01 Background: Pilates exercises help stabilize the vertebral segments by recruiting the abdominal and spinal muscles. Pilates training may increase joint stability and improve neuromuscular efficiency (NME). Objective: This study aimed to evaluate NME of the multifidus (MU) muscle through electromyography (EMG) analysis and torque test, applied to practitioners and non-practitioners of Pilates. Methods: Participants included thirty women: Pilates practitioners (n = 15) and non-practitioners (n = 15). They were tested for trunk extension. Their right and left MU muscles were submitted to EMG to estimate NME. Results concerning torque, EMG, and NME from all participants were compared. Results: Statistical analysis concerning isometric torque peak (p = 0.0275) and NME (p = 0.0062) showed significant difference (Student t test; p < 0.05) between practitioners and control. No significant difference (p = 0.3387) in EMG was observed. Conclusion: Our results suggest Pilates exercises is effective in training spinal muscles to improve NME in women. Department of Morphology (Anatomy) Piracicaba Dental School University of Campinas (UNICAMP) Department of Physical Education São Paulo State University (UNESP) Department of Physical Education São Paulo State University (UNESP)

Neuromuscular fatigue (NMF) is usually assessed non-invasively in healthy, athletic or clinical populations with the combination of voluntary and evoked contractions. Although it might appear relatively straightforward to magnetically or electrically stimulate at different levels (cortical/spinal/muscle) and to measure mechanical and electromyographic responses to quantify neuromuscular adjustments due to sustained/repeated muscle contractions, there are drawbacks that researchers and clinicians need to bear in mind. The aim of this opinion paper is to highlight the pitfalls inevitably faced when NMF is quantified. The first problem might arise from the definition of fatigue itself and the parameter(s) used to measure it; for instance, measuring power vs. isometric torque may lead to different conclusions. Another potential limitation is the delay between exercise termination and the evaluation of neuromuscular function; the possible underestimation of exercise-induced neural and contractile impairment and misinterpretation of fatigue etiology will be discussed, as well as solutions recently proposed to overcome this problem. Quantification of NMF can also be biased (or not feasible) because of the techniques themselves (e.g. results may depend on stimulation intensity for transcranial magnetic stimulation) or the way data are analyzed (e.g. M wave peak-to-peak vs first phase amplitude). When available, alternatives recently suggested in the literature to overcome these pitfalls are considered and recommendations about the best practices to assess NMF (e.g. paying attention to the delay between exercise and testing, adapting the method to the characteristics of the population to be tested and considering the limitations associated with the techniques) are proposed.

The purpose of this study was to demonstrate the differences in shoulder muscle strength, cross-sectional area of the rotator cuff muscles, acromiohumeral distance, and supraspinatus tendon thickness between symptomatic and asymptomatic patients with rotator cuff tears.Thirty-two symptomatic patients and 23 asymptomatic patients with rotator cuff tears participated in this study. Data of the patients with any type of tear and supraspinatus tear were analyzed. We evaluated the isometric torque, cross-sectional area of the rotator cuff muscles, supraspinatus tendon thickness, acromiohumeral distance, range of motion, and Western Ontario Rotator Cuff Index.Asymptomatic patients showed greater isometric torque of shoulder abduction and internal rotation than symptomatic patients with any type of tear (P ≤ .01). Asymptomatic patients also demonstrated greater cross-sectional area of the supraspinatus (P.01); however, there was no significant difference in the cross-sectional area of the other cuff muscles. There was also no significant difference in the supraspinatus tendon thickness (P = .10). The acromiohumeral distance at 90° of shoulder abduction was larger (P = .04) in asymptomatic patients. Additionally, similar tendencies were observed in the results of patients with supraspinatus tears, except for the isometric torque of shoulder external rotation. This torque was greater (P.01) in asymptomatic patients.Asymptomatic patients showed greater shoulder range of motion, muscle strength of shoulder abduction and internal rotation, small occupation ratio of supraspinatus tendon thickness as a percentage of acromiohumeral distance, and large cross-sectional area of supraspinatus.

This study examined whether changes in strength following a moderate-duration strength training program were associated with changes in specific combinations of anatomical and neuromuscular variables. 36 men (18–40 y) completed 10 weeks of lower-limb heavy resistance (6-RM) strength training. Measurements included cross-sectional area (CSA), fascicle length (lf) and fascicle angle (θf) from proximal, middle and distal regions of the four quadriceps components; agonist (EMG:M), antagonist (EMG) muscle activities and percent voluntary quadriceps activation (%VA; interpolated twitch technique); patellar tendon moment arm distance; and maximal isometric, concentric and eccentric (60° s–1) torque. Multiple regression models were developed to quantify the relationship between the change in maximum torque and the changes in combinations of anatomical and neuromuscular variables. The best model for each contraction mode was determined using Akaike’s Information Criterion (AICc), an information-theoretic approach for model selection. Strength increased significantly following training (mean range = 12.5–17.2%), and moderate relationships were observed between modeled data (using best-fit prediction models) and the change in torque for each contraction mode. The change in isometric torque was best (although weakly) predicted by the linear combination of the change in proximal-region vastus lateralis (VL) CSA and fascicle angle (R2 = 0.27, p < 0.05; AICcwi = 0.52, i.e., the probability the model would be selected as the “best model”). The models best predicting the change in concentric and eccentric torque both included the combination of the change in quadriceps (i.e., mean of all muscles) EMG:M and the change in vastus intermedius fascicle angle combined with either a change in proximal-region VL (R2 = 0.40, p < 0.001; AICcwi = 0.15) or whole quadriceps (R2 = 0.41, p < 0.001; AICcwi = 0.30) CSA (concentric and eccentric, respectively). Models incorporating the change in proximal CSA typically received substantial support (AICC < 2) for concentric torque prediction models, and the change in % VA and pre-training moment arm distance had substantial support for use in eccentric torque prediction models. In conclusion, adaptations varied between individuals, however strength training programs targeted to improve a group of variables that particularly includes agonist muscle activation might yield the greatest improvements in concentric and eccentric knee extension strength, whereas proximal muscle size and fascicle angle appear most important for isometric torque improvements.

The purpose of this study was to compare the effect of a 6‐week period of knee flexion strength training at either optimal or short muscle length, on length‐specific muscle strength and fatigue. Twelve healthy volunteers performed dynamic (isokinetic concentric) training with one leg at short and the contralateral leg at optimal muscle length for 6 weeks. Knee flexor muscle strength was assessed before and after training, comprising maximal voluntary isometric and dynamic contractions at short, intermediate and near optimal muscle length and electrically evoked, contractions at near optimal length only. Fatigability was tested by performing 60 maximal concentric contractions at either short or optimal muscle length. Isometric torque at all muscle lengths improved equally by training at short and optimal muscle length, for example, tested at short 18 (17) versus 21 (17) % (CI) and at optimal 14 (8) versus 17 (16) % muscle length, respectively. Likewise, equal improvements were observed for dynamic contractions in both groups. Prior to training, fatigue induced at optimal muscle length tended to be more pronounced than at short muscle length (fatigue‐indexes −41 (6) vs. −34 (7) %, respectively, P = 0.05). However, training at either length did not reduce fatigability. Training with maximal concentric contractions at either short or optimal muscle length for 6 weeks improved isometric and dynamic muscle strength in the entire range of motion without inducing any discernible length‐specific adaptations. However, strength training at restricted muscle length did not reduce relative fatigue when induced at either short or optimal muscle length.

International audience; Locomotor exercise may induce corticospinal excitability and/or cortical inhibition change in the knee extensors. This study investigated whether the mode of muscle contraction involved during a locomotor exercise modulates corticospinal and intracortical responsiveness. Eleven subjects performed two 45-min treadmill walking exercises in an uphill (+ 15%) or a downhill (− 15%) condition matched for speed. Maximal voluntary isometric torque (MVIC), voluntary activation level (VAL), doublet (Dt) twitch torque, and M-wave area of the knee extensors were assessed before and after exercise. At the same time-points, motor-evoked potential (MEP), cortical silent period (CSP), and short-interval cortical inhibition (SICI) were recorded in the vastus lateralis (VL) and rectus femoris (RF) muscles. After exercise, uphill and downhill conditions induced a similar loss in MVIC torque (− 9%; p

Background and Purpose: The effect of knee angle on electrically elicited quadriceps muscle torque has not been established. The goal of this study was to determine which knee angle allowed for the production of the greatest knee extensor maximal voluntary isometric torque (KEMVIT), the greatest electrically elicited torque, and the highest percent of KEMVIT from the knee extensor muscles. Case Description: Eighteen participants were secured in a force dynamometer with the knee positioned at 30°, 60°, and 90° flexion. Participants performed KEMVITs followed by electrically elicited contractions to their maximum tolerance. Outcomes: The mean ± SD of the peak KEMVITs was 123.7 ± 35.7 Nm, 222.6 ± 67.1 Nm, and 248.2 ± 81.1 Nm at 30°, 60°, and 90°, respectively. Significantly greater KEMVITs were produced at 60° and 90° than at 30° (p < 0.001). The mean ± SD of the maximally tolerated electrically elicited torques was 71.8 ± 18.8 Nm, 170.9 ± 70.4 Nm, and 134.6 ± 72.6 Nm at 30°, 60°, and 90°, respectively. Significantly higher torques were tolerated at 60° than at 30° (p < 0.001) and 90° (p = 0.018). The mean ± SD of the percent KEMVITs was 59.7 ± 11.7%, 78.2 ± 23.8%, and 52.6 ± 18.7% at 30°, 60°, and 90°, respectively. Significantly greater percent KEMVITs were produced at 60° than at 30° (p = 0.001) and 90° (p < 0.001). Discussion: Electrically elicited quadriceps torque production is greater at 60° as compared to 30° and 90° knee flexion.

NEW FINDINGS What is the central question of this study? Why do some subjects recover slowly following a bout of eccentric exercise and why is recovery faster following a repeated bout? What is the main finding and its importance? The results are consistent with two major causes of the reduction of quadriceps torque, the onset of low-frequency fatigue which recovered relatively fast and a second, delayed form of damage. Differences in the delayed damage process largely accounted for the differences in the rate of torque recovery between subjects after a first bout and it was suppression of the delayed damage which accounted for the faster recovery following a repeated bout of eccentric exercise. ABSTRACT The purpose of this study was to determine the extent to which low-frequency fatigue (LFF) accounts for the loss of quadriceps strength and time course of recovery following a series of drop jumps (DJs). Seventeen female subjects (20.8 ± 1.4 years) undertook 100 DJs, which were repeated 4 weeks later. Maximum isometric torque (MIT) and the ratio of torque generated by 20 and 100 Hz electrical stimulation (20/100), as a measure of LFF, were measured over 7 days following each series of DJs. After the first series the 20/100 ratio fell to a greater extent than MIT (to 35 ± 8.7% and 69 ± 11%, respectively) but recovered over 2-3 days, while MIT showed little recovery over this time. Changes of the 20/100 ratio were similar between subjects with fast or slow MIT recovery. Following the second series of DJs, changes in the 20/100 ratio were similar to those of the first bout and there were no differences between fast and slow recovering subjects. MIT, however, recovered more rapidly than after the first bout; the faster recovery was confined to the subjects who recovered slowly following the first bout. The results are consistent with two major causes of the reduction of quadriceps torque, the onset of low-frequency fatigue which recovered relatively fast and a second, delayed, form of damage. The latter largely accounted for the differences in MIT recovery between subjects after the first bout, while suppression of the delayed damage accounted for the faster recovery following the repeated bout.

Made available in DSpace on 2019-10-04T12:13:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-06-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Objectives: Strenuous exercise can impair athletic performance due to muscular inflammation and oxidative stress. Antioxidants such as cocoa flavanols have been used as a supplement to prevent oxidative stress; however, the benefits of dietary antioxidants for athletic performance after muscle soreness (MS) is unclear. The purpose of this study was to examine the effects of cocoa flavanols after a MS inducing protocol. Methods: In a randomized, double-blinded design, 13 male collegiate rugby players consumed either chocolate milk (CHOC) or chocolate milk with additional cocoa flavanols (CocoaCHOC) during a 7-d loading phase. MS was induced by a drop jump protocol on day 5 of the intervention. Athlete performance was assessed with vertical-jump and yo-yo tests and subjective measures of soreness 5 d before and 2 d post-MS protocol. Urinary markers of oxidative stress (isoprostanes) were assessed before and 48 h post-MS. Results: No changes were observed between the groups over time for isometric torque (P=.63), vertical jump performance (P=.39), and yo-yo testing (P =.57) between the trials. No interaction was found in isoprostanes levels between the trials (CocoaCHOC baseline: 88 +/- 0.38 pg/mL and 48 h post-MS: 81 +/- 0.53 pg/mL; P=.82; and CHOC baseline: 98 +/- 0.96 pg/mL and 48 h post-MS: 96 +/- 0.38 pg/mL; P=.59). No main effect (treatment x time; P = .58) was observed for isoprostanes. Although not significant, the CocoaCHOC group ran 97 meters further than the CHOC group in the yo-yo test. Conclusions: Cocoa flavanols added to a post-exercise recovery beverage for 7 d has no oxidative stress or athletic performance benefits. (C) 2018 Published by Elsevier Inc. State Univ Sao Paulo, Fac Pharmaceut Sci, Dept Food & Nutr, Postgrad Program Food & Nutr, Sao Paulo, Brazil Univ Sao Paulo, Sch Phys Educ & Sport Ribeirao Preto, Sao Paulo, Brazil Cent Washington Univ, Dept Hlth Sci, Ellensburg, WA USA State Univ Sao Paulo, Fac Pharmaceut Sci, Dept Food & Nutr, Postgrad Program Food & Nutr, Sao Paulo, Brazil CAPES: 001

Madison, G, Patterson, SD, Read, P, Howe, L, and Waldron, M. Effects of small-sided game variation on changes in hamstring strength. J Strength Cond Res 33(3): 839-845, 2019-Small-sided games (SSGs) are commonly used by soccer practitioners to condition players. This form of exercise can result in fatigue, potentially exposing the muscle to injury risk. The purpose of this study was to determine the effects of SSG variations on hamstring torque in semiprofessional soccer players. In a counterbalanced cross-over design, 10 male semiprofessional soccer players took part in both small relative area (3 vs. 3; 300 m) and large relative area (4 vs. 4; 1000 m) SSGs. The games comprised 6 × 4-minute bouts, with 90-second recovery. Both movement and heart rate responses were monitored by global positioning systems (GPS) and hamstring isometric torque was measured pre-training and post-training using a NordBord. There were differences (p < 0.05) between the small and large relative area games for peak hamstring force decrement (5.78 N and -13.62 N, respectively) and mean hamstring force decrement at 90° (11.11 N and -4.78 N, respectively). The number of accelerations was related to (r = 0.46, p = 0.039) reduced hamstring peak torque at 90°. In conclusion, larger relative area SSGs elicited the greatest internal and external loads, resulting in decrements in hamstring force. The number of accelerations performed in the session increases the likelihood of hamstring fatigue and can be controlled with the relative pitch area.

Following exercise-induced muscle damage (EIMD), masters athletes take longer to recover than younger athletes. The purpose of this study was to determine the effect of higher than recommended postexercise protein feedings on the recovery of knee extensor peak isometric torque (PIT), perceptions of recovery, and cycling time trial (TT) performance following EIMD in masters triathletes. Eight masters triathletes (52 ± 2 y, V̇O2max, 51.8 ± 4.2 ml•kg-1•min-1) completed two trials separated by seven days in a randomized, doubleblind, crossover study. Trials consisted of morning PIT testing and a 30-min downhill run followed by an eight-hour recovery. During recovery, a moderate (MPI; 0.3 g•kg-1•bolus-1) or high (0.6 g•kg-1•bolus-1) protein intake (HPI) was consumed in three bolus feedings at two hour intervals commencing immediately postexercise. PIT testing and a 7 kJ•kg-1 cycling TT were completed postintervention. Perceptions of recovery were assessed pre- and postexercise. The HPI did not significantly improve recovery compared with MPI (p > .05). However, comparison of within-treatment change shows the HPI provided a moderate beneficial effect (d = 0.66), attenuating the loss of afternoon PIT (-3.6%, d = 0.09) compared with the MPI (-8.6%, d = 0.24). The HPI provided a large beneficial effect (d = 0.83), reducing perceived fatigue over the eight-hour recovery (d = 1.25) compared with the MPI (d = 0.22). Despite these effects, cycling performance was unchanged (HPI = 2395 ± 297 s vs. MPI = 2369 ± 278 s; d = 0.09). In conclusion, doubling the recommended postexercise protein intake did not significantly improve recovery in masters athletes; however, HPI provided moderate to large beneficial effects on recovery that may be meaningful following EIMD.

Recent research has reported that lower maximal rate of torque development (dτ/dt max) exhibited by females, relative to males, during knee extension can be accounted for by normalization to a maximal voluntary contraction (MVC); however, this was not seen in the upper limb. The aim of the current work was to examine the contribution of maximum strength (τmax), twitch contraction time (CT), muscle fiber condition velocity (MFCV), and rate of muscle activation (Q30) to sex-differences in the dτ/dt max during maximal isometric dorsiflexion. Thirty-eight participants (20 males; 18 females) performed both maximal voluntary and evoked isometric contractions of the tibialis anterior across 3 days. Ten maximal compound muscle action potentials were elicited and subsequently followed by three, 5-s contractions. From the recordings, MFCV, dτ/dt max, τmax, CT, electromechanical delay (EMD), root-mean squared (RMS) amplitude, peak-to-peak voltage (Vpp), and Q30 were calculated. An ANCOVA showed that τmax accounted for all the sex-differences in dτ/dt max (p = 0.96). There were no significant differences between groups with respect to MFCV, RMS amplitude, Vpp amplitude, or CT. However, there was a significant sex-difference in dτ/dt max, τmax, and Q30. Females had longer evoked EMD times compared with males (15.69 ± 10.57 ms versus 9.95 ± 3.46 ms; p = 0.01), but the voluntary EMD times were not different. The current research supports the work by Hannah et al. Exp Physiol 97:618–629, (2012) that normalization to MVC in the quadriceps is able to account for all sex-differences in rate of toque development in the lower limb.

Previous results have shown experimental evidence that the muscle response to neuromuscular electrical stimulation (NMES) is delayed; the time lag is often referred to as electromechanical delay. NMES closed-loop control methods have been developed to compensate for a known constant input delay. However, as a muscle fatigues, this delay increases. This paper develops a feedback controller that robustly compensates for the time-varying delay of an uncertain muscle model during isometric contractions. The controller is proven to yield global uniformly ultimately bounded torque tracking error. Experimental results illustrate the effectiveness of the developed controller and the time-varying nature of the delayed response.

Del Vecchio, L, Stanton, R, Reaburn, P, Macgregor, C, Meerkin, J, Villegas, J, and Korhonen, MT. Effects of combined strength and sprint training on lean mass, strength, power, and sprint performance in masters road cyclists. J Strength Cond Res 33(1): 66-79, 2019-Strength and sprint-training exercises are integral part of training in many younger endurance cyclists to improve cycling efficiency and sprinting ability. This study was undertaken to examine whether muscle and performance characteristics could be improved in endurance-trained masters cyclist by adding strength and sprint-training stimuli into their training regimen. Twenty-five masters road cyclists were assigned to a combined strength and sprint-training group (CT; n = 9, 53.5 ± 9.3 years), a sprint-training group (ST, n = 7, 49.4 ± 4.8 years) or a control group (CG, n = 9, 56.9 ± 8.6 years). Before and after the 12 weeks intervention, whole body lean mass, total lower limb lean mass (LLLM), countermovement jump height, peak isometric torque of quadriceps and hamstring muscles were examined. For evaluation of sport-specific performance, 10-second sprint cycling peak power (PP10), total 30 seconds work (TW), PP output and flying 200-m time trial (TT) performance were assessed. No pretraining differences were observed between CT, ST, and CG groups for any of the dependant variables. After training, a significant (p < 0.05) between group difference was observed in TW between CT and CG groups. A significant effect of time (p < 0.05) was observed for LLLM in CT and ST groups, and for TT in the CT group. These results suggest including strength and sprint exercises in training can increase LLLM and sprint performance in endurance-trained masters road cyclists. Further research is warranted to find out an ideal pattern of training to maintain aerobic capabilities along with sprint performance in aging road cyclists.

Evaluating the rate of torque development (RTD) in isometric ballistic contraction targeting submaximal torques is usually overlooked in the literature. In a series of isometric ballistic contractions targeting a range of submaximal torque values, there is a linear relationship between the peak torque and the peak RTD obtained in each contraction. RTD scaling factor (RTD-SF) represents the slope of this relationship. In this study, we investigated the prevalence of interlimb asymmetry in the RTD-SF and in the RTD calculated across submaximal torques. Furthermore, we compared these asymmetry indices with those calculated adopting more classical approaches, such as ballistic contraction targeting maximal torque and isokinetic concentric conditions. Quadriceps and hamstrings strength was evaluated in both limbs of elite under 17 and under 19 soccer players (20 males, 17 ± 1 years). Participants performed three concentric isokinetic contractions at 240°/s and a series of isometric ballistic contractions targeting from 20 to 100% of maximal isometric torque. The interlimb difference was calculated for each parameter and players presenting an interlimb difference >15% were identified. A total of 40% (for quadriceps) and 60% (for hamstring) of players showed an interlimb asymmetry in isometric RTD for at least 50% of submaximal torque range. The RTD-SF was able to identify more players with asymmetry than the classical isokinetic tests. However, isokinetic and isometric indices of asymmetry were in general poorly or not correlated with each other. Most players presented an interlimb asymmetry in RTD for a wide part of the torque range and the adopted protocol was able to highlight important interindividual differences. Furthermore, players showed a large prevalence of RTD-SF asymmetry in both quadriceps and hamstrings. It is still to be determined if these asymmetries are functionally relevant. Nevertheless, the adopted protocol provided meaningful information for identifying interlimb asymmetries that could not be gathered when adopting the classical method of ballistic contractions targeting only maximal torques.

Introdução: Testes funcionais que se assemelham a prática esportiva vem sendo utilizados para análise do movimento e possível fator minimizador de lesões. A força da musculatura do quadril apresenta bom componente para a melhora da execução de movimento impedindo movimentos excessivos do joelho, como o valgo dinâmico, que é um fator relacionado a lesões do ligamento cruzado anterior, porém, a relação do torque isométrico com o valgo dinâmico ainda não está bem estabelecida. Objetivos: comparar o pico de medialização do joelho de jogadores de futebol profissional, em três testes funcionais com exigências diferentes, sob análise cinemática bidimensional, e a sua correlação o torque isométrico dos músculos abdutores e extensores de quadril. Metodos: A amostra foi composta por 19 jogadores de futebol profissional. O torque isométrico foi coletado através do dinamômetro manual Lafayette. A cinemática bidimensional foi utilizada para avaliar três testes funcionais de diferentes exigências, Single Limb Squat, Lateral Step Down Test e Single Leg Drop Landing Tests. Resultados: Não foram encontradas diferenças significativas entre os valores de valgo dinâmico de joelho nos três testes funcionais do lado direito, diferentemente do esquerdo. E não se estabeleceu relação entre o torque isométrico de quadril e o valgo dinâmico de joelho em nenhum dos testes funcionais. Conclusão: Conclui-se que o torque isométrico de extensores e abdutores de quadril não apresentou correlação com o pico de valgo dinâmico do joelho durante diferentes tarefas funcionais, e que a comparação entre essas tarefas pode apresentar diferenças significativas. Introduction: Functional tests that resemble sports practice have been used for analysis of movement and possible minimization factor of lesions. The strength of the hip musculature presents a good component for the improvement of motion execution preventing excessive knee movements, such as dynamic Valgus, which is a factor related to anterior cruciate ligament lesions, however, the ratio of the torque Isometric with dynamic valgus is not well established yet. Objectives: To compare the peak of medialization of the knee of professional football players, in three functional tests with different requirements, under two-dimensional kinematic analysis, and its correlation the isometric torque of the19 abductors and extensor muscles of Hip. Methods: The sample was composed of 19 professional football players. The isometric torque was collected through the Lafayette manual dynamometer. The two-dimensional kinematics were used to evaluate three functional tests of different requirements, single Limb Squat, side Step Down test and single Leg Drop landing tests. Results: No significant differences were found between the dynamic knee valgus values in the three functional tests on the right side, unlike the left. And no relationship was established between the hip isometric torque and the dynamic knee valgus in any of the functional tests. Conclusion: It is concluded that the isometric torque of extenders and hip abductors did not present correlation with the dynamic Valgus peak of the knee during different functional tasks, and that the comparison between these tasks may have differences Significant. Coordenação de Aperfeiçoamento de Pessoal de Nível Superior