Effects of the Nordic Hamstring exercise on sprint capacity in male football players: a randomized controlled trial

This assessor-blinded, randomized controlled superiority trial investigated the efficacy of the 10-week Nordic Hamstring exercise (NHE) protocol on sprint performance in football players.

Thirty-five amateur male players (age: 17–26 years) were randomized to a do-as-usual control group (CG; n = 17) or to 10-weeks of supervised strength training using the NHE in-season (IG; n = 18). A repeated-sprint test, consisting of 4 × 6 10 m sprints, with 15 s recovery period between sprints and 180 s between sets, was conducted to evaluate total sprint time as the primary outcome. Secondary outcomes were best 10 m sprint time (10mST) and sprint time during the last sprint (L10mST). Additionally, peak eccentric hamstring strength (ECC-P_HS) and eccentric hamstring strength capacity (ECC-CAP_HS) were measured during the NHE.

Ten players were lost to follow-up, thus 25 players were analyzed (CG n = 14; IG n = 11). Between-group differences in mean changes were observed in favor of the IG for sprint performance outcomes; TST (?0.649 s, p = 0.056, d = 0.38), 10mST (?0.047 s, p = 0.005, d = 0.64) and L10mST (?0.052 s, p = 0.094, d = 0.59), and for strength outcomes; ECC-P_HS (62.3 N, p = 0.006, d = 0.92), and ECC-CAP_HS (951 N, p = 0.005, d = 0.95).

In conclusion, the NHE showed small-to-medium improvements in sprint performance and large increases in peak eccentric hamstring strength and capacity.

Trial Registration Number: NCT02674919     

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.     

A simplified approach to teaching medical students ocular movements and the rationale in testing the oculomotor,trochlear, and abducent nerves

The actions of the individual extraocular muscles are best explained to medical students in a lecture format by showing the relationship of each muscle to the axes of the globe and the walls of the bony orbit. The lateral and medial rectus muscles cross only the vertical axis, and consequently, cause only abduction and adduction, respectively. These muscles can be tested simply by asking the patient to abduct or adduct. Inability to do so indicates that the muscles and/or their innervation have been compromised. In contrast, the superior and inferior oblique and rectus muscles cross all three axes (vertical, horizontal, and anteroposterior) of the globe. Therefore, concentric contraction of each of these muscles results in three movements; abduction or adduction, elevation or depression, and intorsion or extorsion. These muscles must be tested with a sequence of two movements. Gaze can be either elevated or depressed by both an oblique and a rectus muscle. If abduction or adduction occurs first, one muscle of the pair becomes incapable of causing elevation or depression of the pupil. The rationale for abducting or adducting first is that either the oblique or rectus muscle of the pair will no longer cross the horizontal axis and will then be unable to effect the desired movement. Inability to elevate or depress gaze from the abducted or adducted position shows which muscle, the oblique or rectus, and/or its innervation has been compromised. Anat Sci Ed 1:126–129, 2008. © 2008 American Association of Anatomists.     

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.     

An electromyographic comparison of a modified version of the plank with a long lever and posterior tilt versus the traditional plank exercise

The purpose of the study was to compare core muscle activation of the tradition prone plank with a modified version performed with a long-lever and posterior-tilt using surface electromyography. To further determine if a specific component of this modified plank was more effective than the other in enhancing muscle activity, the plank with a long lever and the plank with a posterior pelvic tilt were studied individually. Nineteen participants performed all four variations of the plank for 30 seconds in a randomized order with 5-minute rest between exercise bouts. Compared to the traditional prone plank, the long-lever posterior-tilt plank displayed a significantly increased activation of the upper rectus abdominis (p < 0.001), lower abdominal stabilizers (p < 0.001), and external oblique (p < 0.001). The long-lever plank showed significantly greater activity compared to the traditional plank in the upper rectus abdominis (p = 0.015) and lower abdominal stabilizers (p < 0.001), while the posterior tilt plank elicited greater activity in the external oblique (p = 0.028). In conclusion, the long-lever posterior-tilt plank significantly increases muscle activation compared to the traditional prone plank. The long-lever component tends to contribute more to these differences than the posterior-tilt component.     

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。     

论短跑项目的专项肌力及伸展性

从运动解剖学角度分析原动肌力量大小和对抗肌伸展性不足是影响短跑步幅的主要因素， 指出增大步幅、提高短跑速度可以通过改善下肢对抗肌的伸展性和提高原动肌肌力来实现。