Angle-specific knee muscle torques of ACL-reconstructed subjects and determinants of functional tests after reconstruction

The purposes of this study were to analyse (a) if “angle-specific” (AS) flexor and extensor torques were different between ACL-reconstructed and uninvolved limbs, (b) the difference in peak torque occurrence angles for concentric and eccentric knee flexor and extensor torques between involved and uninvolved limbs and (c) if AS concentric and eccentric knee flexor and extensor torques are determinants of performance in the “single-leg hop test” (SLHT) and “vertical jump and reach test” (VJRT) in ACL-reconstructed legs. Twenty-seven male ACL-reconstructed volunteers were included in the study. Isokinetic knee muscle strength, SLHT and VJRT were performed 6 months after ACL reconstruction. No difference was found in extremity and knee joint angle interaction for concentric and eccentric flexor and extensor torques (p > 0.05). Peak torque occurrence angles were not different between involved and uninvolved limbs (p > 0.05). In involved extremities, concentric knee extensor strength at 90° was a determinant of SLHT performance (R² = 0.403, p < 0.05), and concentric knee extensor strength at 60° was a determinant of VJRT (R² = 0.224, p < 0.05). Assessment of AS concentric knee extensor strength at 60° and 90° might be important, because these were determinants of functional test performance.     

等速向心运动中膝关节屈伸肌群的sEMG研究

本文对女子柔道运动员等速向心运动过程膝关节屈伸肌群的表面肌电与运动速度以及峰力矩之间的关系进行了探讨,以期为进一步的研究以及力量测试、训练和评价提供参考。     

不同角速度下自行车运动员膝关节肌力特征的研究

方法：利用CONTREX等速肌力测试与训练系统,以180°／s、120°／s、60°／s3种角速度对苏州市自行车训练队26名运动员右腿膝关节进行等速向心屈伸测试。目的：分析自行车运动员不同角速度下等速向心收缩与膝关节肌肌力的关系及肌力特征。结果：1、屈伸肌峰力矩随速度的增加呈减小趋势。2、到达峰力矩的时间随测试速度的增加而缩短。且男女运动员在180°／s与120°／s组间均无显著差异。3、膝关节相对平均功率伸肌均大于屈肌,120°／ts时,屈伸肌的相对平均功率最大。4、屈伸肌比在64．8％～70．6％内,有随速度增加而增加的趋势。结论：以60°／s的角速度训练肌肉最大力量效果更明显;爆发力在120°／s时训练效果最佳;屈／伸肌比值（H／Q）在正常范围内,但低于优秀运动员（优秀运动员可达80％以上）。     

不同等级散打运动员肘、膝关节肌群等速测试肌力特征研究

结合训练实践,运用ISOMED2000等速测试仪对我国男子散打主力队员膝、肘关节屈伸肌群肌力特征进行测试与分析。结论:不同等级散打运动员肘关节屈伸肌群等速向心、离心收缩、膝关节伸肌群等速离心收缩相对峰力矩值在60°/s、180°/s时具有显著性差异(P<0.05);膝关节屈伸肌群等速向心收缩、屈肌群离心收缩相对峰力矩值在各角速度下具有显著性差异(P<0.05);不同等级散打运动员肘、膝关节屈伸肌群等速向心收缩在300°/s、离心收缩在240°/s时达到力矩梯度最大值,且差异显著。说明基础力量、中快速力量及快速动作爆发力能较好地反映专项运动水平,相对峰力矩、力矩梯度数值越大,专项水平越高。     

Effects of antagonist pre-load on knee extensor isokinetic muscle performance

The aim of this study was to evaluate and compare acute effects of a reciprocal action protocol and a super-set protocol on knee extensor performance during concentric isokinetic exercise. Fourteen men aged 29.4 ± 6.1 years were tested on three different protocols, with 1 min of rest between sets: control (3 sets of 10 isokinetic knee extension repetitions), reciprocal action protocol (3 sets of 10 repetitions of reciprocal isokinetic concentric knee flexion and knee extension repetitions), and super-set protocol (3 sets of a combination of 10 repetitions of knee flexion immediately followed by 10 repetitions of knee extension repetitions). Tests were performed at 60° · s(-1) and 180° · s(-1), randomized across 3 days and separated by at least 72 h. There were no significant differences between protocols for peak torque at 60° · s(-1) or 180° · s(-1). Total work was significantly higher during the reciprocal action protocol compared with the super-set protocol at 60° · s(-1). There was a significant decline in peak torque (from 240.6 to 212.9 N · m) and total work (from 2294 to 1899 J) for the control condition at 60° · s(-1). Also, total work declined significantly across sets for the super-set protocol at 60° · s(-1) (from 2157 to 1707 J). Results indicate that a reciprocal action protocol provides torque maintenance during multiple sets of isokinetic training, both at slow and high velocities.     

A lower extremity strength-based profile of NCAA Division I women’s basketball and gymnastics athletes: implications for knee joint injury risk assessment

This study aimed to provide a comprehensive strength-based physiological profile of women’s NCAA Division I basketball and gymnastic athletes; and to make sport-specific comparisons for various strength characteristics of the knee flexor and extensor muscles. A focus on antagonist muscle balance (hamstrings-to-quadriceps ratios, H:Q) was used to elucidate vulnerabilities in these at-risk female athletes. Fourteen NCAA Division I women’s basketball and 13 gymnastics athletes performed strength testing of the knee extensors and flexors. Outcome measures included absolute and relative (body mass normalised) peak torque (PT), rate of torque development at 50, 100, 200 ms (RTD50 etc.) and H:Q ratios of all variables. The basketball athletes had greater absolute strength for all variables except for isokinetic PT at 240°s^?1 and isometric RTD50 for the knee extensors. Gymnasts showed ~20% weaker body mass relative concentric PT for the knee flexors at 60 and 120°·s^?1, and decreased conventional H:Q ratios at 60 and 240°·s^?1 (~15%). These findings suggest that collegiate level gymnastics athletes may be prone to increased ACL injury risk due to deficient knee flexor strength and H:Q strength imbalance. Coaches may use these findings when implementing injury prevention screening and/or for individualised strength training programming centered around an athletes strength-related deficits.     

The fatigue effect of a simulated futsal match protocol on sprint performance and kinematics of the lower limbs

This study aimed to investigate the fatigue effects induced by a futsal-specific protocol (FIRP) on sprint performance and the kinematics of the lower limbs. Twenty-one futsal players participated in this study and performed a protocol to simulate the futsal demands. At pre-protocol, half-time and post-protocol, the athletes performed 10-m sprints that were recorded for kinematic analysis. Continuous relative phase (CRP) was calculated to assess the inter-segmental coordination. In addition, vertical (K_VERT) and leg (K_LEG) stiffness were calculated. Analysis of variance (ANOVA) for repeated measures was used (P < 0.05). The main results showed that sprint time increased (P < 0.01) post-protocol when compared to pre- and half-time conditions. Lower values of the step rate (P = 0.01) and higher values of the leg angular velocity (P = 0.02) were verified at the end of the FIRP. The CRP of thigh–leg and leg–foot and the stiffness did not change over the protocol. In addition, the high correlation of CRP between the conditions revealed no changes in coordination pattern. We concluded that futsal related-fatigue induced a decrement on sprint time, changing the kinematics of the lower limbs (decreasing step rate and increasing leg angular velocity). However, neither stiffness nor intersegment coordination during sprints was affected by fatigue.     

优秀投掷运动员核心力量等速肌力测试研究

目的:分析浙江师范大学投掷训练队优秀运动员腰背肌的生物力学特征,探讨投掷运动员的成绩与腰背屈伸肌群力量的关系,为投掷训练和易受伤部位的预防提供理论依据。方法:利用德国Isomed2000等速肌力测试系统进行核心力量等速肌力测试,测试严格按照Isomed2000等速测试系统使用手册的要求进行操作。结果:优秀投掷运动员腰背屈伸肌群等速向心收缩峰力矩随测试速度(30°/s~180°/s)的增加大体呈递减趋势,且随着角速度的增大,优秀投掷运动员的腰背屈伸肌群等速向心收缩峰力矩下降幅度(斜率K:伸-0.884小于屈-0.655)比普通人(K:伸-0.275小于屈-0.035)小,且优秀投掷运动员伸肌最大峰力矩的下降幅度要比屈肌小;在角速度为30°/s到120°/s时,最大功率随着给定角速度的增大而增大,在180°/s时又有所减小;腰背屈伸肌群峰力矩的角度在30°/s到180°/s时伸肌55.5°~58°大于屈肌的54.5°~56.25°,随着角速度的增大,大体呈上升趋势,在30°/s时峰力矩角度最小。     

青年男子举重运动员肘关节屈伸肌群等速肌力特征

通过分析青年男子举重运动员肘关节屈伸肌群的力量参数,探讨肘关节屈伸肌群在举重专项训练中的作用,为预防肘关节损伤及科学训练提供理论依据。采用Cybex—Norm型等速测力与康复系统,在预定角速度90°／s．180°／s和300°／s下对上海举重队9名青年男子举重运动员肘关节进行等速向心屈伸肌力测试。结果发现举重运动员肘关节屈伸肌群相对峰力矩、相对总劝和相对平均功率随着运动速度的增大而减小,屈伸肌群峰力矩比值接近1．0。表明举重项目中肘关节屈伸肌群主要功能是维持运动中关节的稳定性,而两侧肘关节同名肌群肌力素质的不均衡性可能是阻碍专项能力韦黾高的重要因素和诱发运动性伤病的潜在因素。     

高水平女子散打运动员不同赛前时期膝关节屈伸肌等动力量变化研究

为了解我国高水平女子散打运动员不同赛前时期膝关节屈伸肌等动力量的水平与特征,选择上海体育学院女子散打运动员19名作为研究对象,选取整个赛前集训中一个周期的训练作为训练周期,按经典分期理论进行训练分期。等速肌力的测试采用CONTREX等动测试系统,以向心和离心60°/s的恒定角速度下进行右膝关节测试,同时测试0.2s快速屈伸时的最大伸肌力矩。研究结果:优秀女子散打运动员屈肌相对峰力矩值是(1.13±0.15)Nm/kg,伸肌相对峰力矩值为(2.11±0.33)Nm/kg,屈伸肌力矩比值是(53.0±4.0)%,比赛期达到最高值。健将级女子散打运动员的0.2s最大相对屈肌力矩为(1.053±0.207)Nm/kg,伸肌相对最大力矩健将级为(1.795±0.295)Nm/kg。结论:运动员水平越高,膝关节屈肌力量越高,屈伸肌力矩比值越大,不同赛期屈肌力量不同,比赛期达到最高。     

综合力量训练对中国女子篮球运动员腰、膝、踝等速力量的影响

目的:了解在常规力量训练基础附加核心力量训练及振动训练方法对国家女子篮球队18名运动员腰背、膝关节、踝关节等速肌力的影响。方法:采用Pneu VIBE振动训练台对国家女子篮球运动员进行振动刺激力量训练,振动频率为25～40 Hz,同时进行核心区肌力训练。经过12周系统的力量训练,应用IsoMed 2000等速测试训练仪器对女子篮球运动员腰腹、膝、踝关节屈伸肌群进行等速力量测试分析。结果:经过12周综合力量训练,女子篮球运动员腰背等速肌力明显上升,屈肌峰力矩(PT)增加了14.35%,背伸肌力量增加了15.65%,差异具有显著性。而下肢力量膝关节峰力矩、屈伸肌峰力矩比率(H/Q)无显著变化。踝关节研究发现,左踝背屈峰力矩训练后稍有减弱,跖屈肌峰力矩以及跖屈/背屈比无显著变化。结论:在常规力量训练中增加先进的核心区训练可有效增加女子篮球运动员腰腹肌力,而振动训练以提高踝、膝关节肌力的方法的有效性需要进一步研究。     

Functional torque ratios and torque curve analysis of shoulder rotations in overhead athletes with and without impingement symptoms

In this study, we evaluated the peak torque, functional torque ratios, and torque curve profile of the shoulder rotators in overhead athletes with impingement symptoms so as to examine possible alterations in response to sports training and shoulder pain. Twenty-one overhead athletes with impingement symptoms were compared with 25 overhead athletes and 21 non-athletes, none of whom were symptomatic for impingement. The participants performed five maximal isokinetic concentric and eccentric contractions of medial and lateral shoulder rotations at 1.57 rad · s(-1) and 3.14 rad · s(-1). Isokinetic peak torque was used to calculate the eccentric lateral rotation-to-concentric medial rotation and the eccentric medial rotation-to-concentric lateral rotation ratios. An analysis of the torque curve profiles was also carried out. The eccentric lateral rotation-to-concentric medial rotation torque ratio of asymptomatic athletes was lower than that of non-athletes at both test velocities. The concentric medial rotation isokinetic peak torque of the asymptomatic athletes, at 3.14 rad · s(-1), was greater than that of the non-athletes, and the peak appeared to occur earlier in the movement for athletes than non-athletes. These findings suggest that there may be adaptations to shoulder function in response to throwing practice. The eccentric medial rotation-to-concentric lateral rotation torque ratio was altered neither by the practice of university-level overhead sports nor impingement symptoms.     

Muscle fatigue induced by exercise simulating the work rate of competitive soccer

Fatigue represents a reduction in the capability of muscle to generate force. The aim of the present study was to establish the effects of exercise that simulates the work rate of competitive soccer players on the strength of the knee extensors and knee flexors. Thirteen amateur soccer players (age 23.3+/-3.9 years, height 1.78+/-0.05 m, body mass 74.8+/-3.6 kg; mean+/-s) were tested during the 2000-2001 soccer season. Muscle strength of the quadriceps and hamstrings was measured on an isokinetic dynamometer. A 90 min soccer-specific intermittent exercise protocol, incorporating a 15 min half-time intermission, was developed to provide fatiguing exercise corresponding in work rate to a game of soccer. The exercise protocol, performed on a programmable motorized treadmill, consisted of the different intensities observed during soccer match-play (e.g. walking, jogging, running, sprinting). Muscle strength was assessed before exercise, at half-time and immediately after exercise. A repeated-measures analysis of variance showed significant reductions (P < 0.001) in peak torque for both the quadriceps and hamstrings at all angular velocities (concentric: 1.05, 2.09, 5.23 rad x s(-1); eccentric: 2.09 rad x s(-1)). The peak torque of the knee extensors (KE) and knee flexors (KF) was greater before exercise [KE: 232+/-37, 182+/-34, 129+/-27, 219+/-41 N x m at 1.05, 2.09 and 5.23 rad x s(-1) (concentric) and 2.09 rad x s(-1) (eccentric), respectively; KF: 126+/-20, 112+/-19, 101+/-16, 137+/-23 N x m] than at half-time (KE: 209+/-45, 177+/-35, 125+/-36, 214+/-43 N x m; KF: 114+/-31, 102+/-20, 92+/-15, 125+/-25 N x m) and greater at half-time than after exercise (KE: 196+/-43, 167+/-35, 118+/-24, 204+/-43 N x m; KF: 104+/-25, 95+/-21, 87+/-13, 114+/-27 N x m). For the hamstrings:quadriceps ratio, significant changes were found (P < 0.05) for both legs, the ratio being greater before than after exercise. For fast:slow speed and left:right ratios, no significant changes were found. We conclude that there is a progressive reduction in muscle strength that applies across a range of functional characteristics during exercise that mimics the work rate in soccer.     

Chain-loaded variable resistance warm-up improves free-weight maximal back squat performance

The acute influence of chain-loaded variable resistance exercise on subsequent free-weight one-repetition maximum (1-RM) back squat performance was examined in 16 recreationally active men. The participants performed either a free-weight resistance (FWR) or chain-loaded resistance (CLR) back squat warm-up at 85% 1-RM on two separate occasions. After a 5-min rest, the participants attempted a free-weight 1-RM back squat; if successful, subsequent 5% load additions were made until participants failed to complete the lift. During the 1-RM trials, 3D knee joint kinematics and knee extensor and flexor electromyograms (EMG) were recorded simultaneously. Significantly greater 1-RM (6.2?±?5.0%; p?p?p?>?.05) was found in concentric EMG, eccentric or concentric knee angular velocity, or peak knee flexion angle. Performing a CLR warm-up enhanced subsequent free-weight 1-RM performance without changes in knee flexion angle or eccentric and concentric knee angular velocities; thus a real 1-RM increase was achieved as the mechanics of the lift were not altered. These results are indicative of a potentiating effect of CLR in a warm-up, which may benefit athletes in tasks where high-level strength is required.     

等动测力及康复训练系统在运动员膝关节损伤后力量训练中的应用

研究利用等动测力及康复系统对膝关节损伤的女运动员进行等速向心训练。经过约8周的训练,患膝屈伸肌群的峰值力矩在不同测试速度下均有显著提高,但伸肌峰值力矩提高较屈肌快。此次研究表明等速向心训练对膝关节损伤后的肌肉功能恢复有一定的促进作用。     

排、篮球运动员膝关节肌力特征的对比与分析

通过对篮、排球各10名一级运动员膝关节进行等动测试分析,结果表明:两项目运动员膝关节肌力特征最主要差异在于伸肌离心收缩能力和屈肌向心收缩能力,膝关节主对抗肌肌力比和同一肌群的离心与向心峰力矩比率上也存在一定差异,这种差异可能与两项目运动员起跳方式有关。     

Functional torque ratios and torque curve analysis of shoulder rotations in overhead athletes with and without impingement symptoms

Abstract

In this study, we evaluated the peak torque, functional torque ratios, and torque curve profile of the shoulder rotators in overhead athletes with impingement symptoms so as to examine possible alterations in response to sports training and shoulder pain. Twenty-one overhead athletes with impingement symptoms were compared with 25 overhead athletes and 21 non-athletes, none of whom were symptomatic for impingement. The participants performed five maximal isokinetic concentric and eccentric contractions of medial and lateral shoulder rotations at 1.57 rad · s^?1 and 3.14 rad · s^?1. Isokinetic peak torque was used to calculate the eccentric lateral rotation-to-concentric medial rotation and the eccentric medial rotation-to-concentric lateral rotation ratios. An analysis of the torque curve profiles was also carried out. The eccentric lateral rotation-to-concentric medial rotation torque ratio of asymptomatic athletes was lower than that of non-athletes at both test velocities. The concentric medial rotation isokinetic peak torque of the asymptomatic athletes, at 3.14 rad · s^?1, was greater than that of the non-athletes, and the peak appeared to occur earlier in the movement for athletes than non-athletes. These findings suggest that there may be adaptations to shoulder function in response to throwing practice. The eccentric medial rotation-to-concentric lateral rotation torque ratio was altered neither by the practice of university-level overhead sports nor impingement symptoms.     

南狮运动员膝关节屈伸肌群生物力学特征分析

南狮运动是我国南方地区广泛开展的民族传统体育项目,具有广大的群众基础,其发展前景甚为广阔。文章采用等速力量测试系统对广州体育学院12名高水平舞狮运动员进行测试,分析比较南狮运动员膝关节屈伸肌群等速收缩肌群峰力矩、屈伸肌比值(H/Q或F/E)、功率(Avg.Power,W)等指标及其肌力的生物力学特征,并应用运动生物力学的原理揭示动作技术特征,旨在为舞狮运动员的选材和教练员的科学训练提供参考依据。     

女子手球运动员踝关节屈伸肌群等速测试与分析

目的：探讨女子手球运动员的踝关节等速测试力量特征。方法：运用CON-TREX对受测试运动员的踝关节进行等速向心测试。结果：受试队员两关节伸肌的相对峰力矩值均显著大于屈肌;女手队员的比值范围在32%～40%之间;踝关节伸肌的平均功率值显著大于屈肌;踝关节伸屈肌的总功值随测试速度的增大而减小。结论：1）女手队员踝关节屈肌最大力量强于伸肌;2）女手队员踝关节屈伸肌力量比例合理;3）女手队员踝关节屈肌的快速力量强于伸肌;4）女手队员踝关节伸屈肌的总工作能力比较弱。     

Reciprocal Versus Nonreciprocal Assessment of Knee Flexors and Extensors in Concentric Actions Using the CON-TREX Multijoint Isokinetic Dynamometer: A Reliability Study

Knee flexor and extensor muscular assessment via isokinetic dynamometry is common practice and established in the research literature. However, reporting assessment methodology regarding reciprocal and nonreciprocal movements is often vague or absent. Such methodological issues are crucial for accurate assessments. Therefore, knee extensor and flexor peak moment using either reciprocal movement or nonreciprocal modalities was assessed. Fifteen participants performed three blocks of five concentric muscle actions at three angular velocities [1: nonreciprocal (maximal active flexion followed by passive extension); B2: reciprocal (maximal active extension followed by maximal active flexion); B3 nonreciprocal (maximal active extension followed by passive flexion)]. ANOVA revealed statistically significant within-subject modality effects for peak knee extensor moment and flexor velocity and modality differences (p < .05). Reciprocal and nonreciprocal assessments give significantly different results, with nonreciprocal giving higher peak moments. Reporting which modality is used is crucial to allow for greater clarity for the reader and practitioner.