Is there really an eccentric action of the hamstrings during the swing phase of high-speed running? Part II: Implications for exercise

We have previously argued that there may actually be no significant eccentric, but rather predominantly an isometric action of the hamstring muscle fibres during the swing phase of high-speed running when the attachment points of the hamstrings are moving apart. Based on this we suggested that isometric rather than eccentric exercises are a more specific way of conditioning the hamstrings for high-speed running. In this review we argue that some of the presumed beneficial adaptations following eccentric training may actually not be related to the eccentric muscle fibre action, but to other factors such as exercise intensity. Furthermore, we discuss several disadvantages associated with commonly used eccentric hamstring exercises. Subsequently, we argue that high-intensity isometric exercises in which the series elastic element stretches and recoils may be equally or even more effective at conditioning the hamstrings for high-speed running, since they also avoid some of the negative side effects associated with eccentric training. We provide several criteria that exercises should fulfil to effectively condition the hamstrings for high-speed running. Adherence to these criteria will guarantee specificity with regards to hamstrings functioning during running. Practical examples of isometric exercises that likely meet several criteria are provided.     

基于两种安排模式下的三级跳远运动员小肌群力量训练效果研究

小肌群训练作为三级跳远运动员最重要的体能训练手段之一,对运动员专项竞技能力的提高具有重要意义。传统三级跳远运动员小肌群训练在安排上具有相对集中的特点。随着对三级跳远运动员专项竞技需要认识的加深,其小肌群训练计划安排的密度、与其它训练因素的组合方式等方面都发生了明显的变化。目前我国高水平三级跳远教练员已经将全新的分散安排模式应用于小肌群训练实践,并取得了较好的训练效果。为分散安排模式小肌群训练的成功应用找到相关理论依据是当前三级跳远理论研究领域中亟待解决的问题。     

核心力量训练对网球运动影响的研究综述

近年来,核心力量训练在体能训练中引起了很多人的关注,但是关于网球运动员核心力量训练的研究在国内学术界仍是一个新的研究课题.文章采用综述的形式参阅了大量的文献,对核心肌肉及核心力量的概念进行探究,通过分析网球技术动作中肌肉的利用,阐明了核心力量对网球运动的重要性,从而帮助人们更好地认识核心力量训练.     

The relationships between hamstring flexibility,lumbar flexion,and low back pain in rowers

Abstract

In this study, we examined the relationships between low back pain, hamstring flexibility, and lumbar flexion in rowers. Twenty-six male university rowers participated. Hamstring flexibility was assessed using an adjusted straight leg raise technique, and lumbar flexion was assessed via a distraction of skin marks protocol while long sitting. A questionnaire ascertained rowing details and low back pain characteristics. Low back pain was highly prevalent. No association was observed between low back pain and hamstring flexibility, or between hamstring flexibility and lumbar flexion. Sufferers of low back pain showed reduced lumbar flexion (P=0.03; 95% confidence interval = ? 3.7 to ?0.2). Results obtained using the adjusted straight leg raise technique suggested that low back pain was not associated with hamstring inflexibility, which suggests that increasing hamstring flexibility for rehabilitation or prevention of low back pain in rowers might not be necessary.     

运动员腘绳肌损伤危险因素的Meta分析

目的:腘绳肌拉伤是体育运动中最常见的损伤之一,且康复难度大复发率高。通过对腘绳肌损伤的危险因素进行综合的Meta分析,有助于深入了解影响腘绳肌拉伤的危险因素,为有效地预防和康复腘绳肌拉伤提供科学依据。方法:收集1992-2014年间国内外公开发表的关于腘绳肌损伤危险因素的研究文献,根据入选标准与排除标准纳入文献并对其质量进行评价,根据入选文献的异质性检验结果,对各危险因素进行随机效应模型或固定效应模型的Meta分析。结果:本次Meta分析结果显示,腘绳肌损伤的主要危险因素为年龄(SMD=0.68,95%CI 0.12~1.25;RR=4.04,95%CI 2.08~7.84),股四头肌最大力矩(SMD=0.58,95%CI 0.19~0.96),腘绳肌损伤史(RR=2.56,95%CI 1.93~3.40;OR=2.98,95%CI 1.30~6.81)。结论:与腘绳肌损伤关联度最大危险因素为年龄的增大,有腘绳肌损伤史和股四头肌最大力矩过大。运动员的身高,体重,腘绳肌最大力矩,腘绳肌肌力与股四头肌肌力比,腘绳肌柔韧性与腘绳肌损伤的发生关联不明显,是否为腘绳肌损伤的主要危险因素尚不确定,还需要进一步的研究证实。     

正手前冲弧圈球技术上肢肌群作用的研究

运用多道肌电遥测仪,对正手前冲弧圈球技术上肢肌群的作用进行了研究,揭示出正手拉前冲弧圈球时上肢肌群作用和发力顺序的本质特征,并提出了发展上肢肌群力量的训练方法.     

浅谈短跑中的肌肉放松

短距离跑是田径运动中主要项目之一，我国短距跑的运动成绩与世界先进水平相比具有一定差距，通过对诸多影响短跑成绩因素中的肌肉放松进行初略探讨，尝试找出一条途径，提高我国短跑运动员的运动技术和运动成绩     

Functional differences in the activity of the hamstring muscles with increasing running speed

Abstract

In this study, we examined hamstring muscle activation at different running speeds to help better understand the functional characteristics of each hamstring muscle. Eight healthy male track and field athletes (20.1 ± 1.1 years) performed treadmill running at 50%, 75%, 85%, and 95% of their maximum velocity. Lower extremity kinematics of the hip and knee joint were calculated. The surface electromyographic activities of the biceps femoris and semitendinosus muscles were also recorded. Increasing the running speed from 85% to 95% significantly increased the activation of the hamstring muscles during the late swing phase, while lower extremity kinematics did not change significantly. During the middle swing phase, the activity of the semitendinosus muscle was significantly greater than that of the biceps femoris muscle at 75%, 85%, and 95% of running speed. Statistically significant differences in peak activation time were observed between the biceps femoris and semitendinosus during 95%max running (P < 0.05 for stance phase, P < 0.01 for late swing phase). Significant differences in the activation patterns between the biceps femoris and semitendinosus muscles were observed as running speed was increased, indicating that complex neuromuscular coordination patterns occurred during the running cycle at near maximum sprinting speeds.     

Fingertip force and electromyography of finger flexor muscles during a prolonged intermittent exercise in elite climbers and sedentary individuals

Abstract

The aim of this study was to characterize forearm muscle fatigue identified by the decrease in electromyogram median frequency and/or fingertip force during intermittent exercise. Nine elite climbers (international competitive level, USA 5.14a on sight) and ten non-climbers were instructed to maintain a fingertip force of 80% of their maximal voluntary contraction force on a dynamometer mimicking a rock climbing grip during a 5 s effort/5 s rest cycle for 36 repetitions (i.e. 6 min of exercise). Elite climbers lasted twice as long as non-climbers (climbers: 3 min; non-climbers: 1 min 30 s) before the force could no longer be maintained (i.e. the failure point). After this moment, fingertip force decreased and stabilized until the end of the exercise around 50% maximum voluntary contraction force in non-climbers and 63% in elite climbers. Electromyogram median frequency showed a greater decrease in non-climbers than in elite climbers before the failure point. No change in median frequency was observed after the failure point in elite climbers or in non-climbers. These results confirm that elite climbers are better adapted than non-climbers for performing the intermittent fingertip effort before the failure point. After this point, the better fingertip force of elite climbers suggests different forearm muscle properties, while the electromyography results do not provide any indication about the fatigue process.     

The Validity of the Sit-and-Reach Test and the Modified Sit-and-Reach Test in Middle-Aged to Older Men and Women

Abstract

A growing concern for the establishment of a national system of education was clearly evident in France during the last decades of the eighteenth century. Physical education was afforded an important role in the educational projections of the period. Beginning with La Chalotais' Essai d'éducation nationale (1763) authors began to express more and more support for the inclusion of a comprehensive program of physical education. Gabriel Coyer's De l'éducation publique (1770), Louis Philipon de la Madelaine's Vues patriotiques sur l'education du peuple (1783) and De l'éducation des collèges (1784), and Jean Ver dier's Maison d'éducation physique et morale (1772) and Cours d'éducation à l'usage des eleves (1777) all contributed significantly to the concept that physical education must constitute an important and integral part of any comprehensive and viable plan for national education. Among the most important deliberations of the various French revolutionary assemblies between 1789 and 1795 were those dealing with education as a concern of the state. Legislators tried valiantly to establish a sound national plan for education. The educational reports and projects presented to the various revolutionary assemblies by Talleyrand, Condorcet, Lepelitier, Lakanal, Romme, and Daunou are usually considered by educational historians to be the most significant. Each of these specified that due attention must be devoted to physical education for children and youth. The proposals, the decrees and the debates which they precipitated did much to attract attention to the importance of the subject. It seems most likely that the period from 1763 to 1795 in France witnessed the establishment of a precedent in modem times for the concept of state concern and support for physical education.