Body Composition and Anthropometric Correlates of Isokinetic Leg Extension Strength of Young Adult Males

Abstract

The present study examined the relative importance of body size and composition as determinants of individual differences in isokinetic leg extensor strength in young adult males performing at slow, moderate, and fast speeds. The subjects were 31 males between the ages of 19 and 29 years, who were not participating in weight training programs. Low to moderate correlations were found between isokinetic strength and body size or body composition measurements. At each speed, similar proportions of the variance in peak torque values were accounted for by lean body weight (23-30%) and thigh volume (20-37%). However, body weight, often suggested as the best reference standard for equalizing strength scores, also accounted for only 13-24% of the variance in peak torque values at each of the speeds tested. The moderate correlations reported in this study do not support the use of body size and composition measurements as a means of adjusting strength values.     

The Effect of Initial Knee Angle on Concentric-Only Squat Jump Performance

Purpose: There is uncertainty as to which knee angle during a squat jump (SJ) produces maximal jump performance. Importantly, understanding this information will aid in determining appropriate ratios for assessment and monitoring of the explosive characteristics of athletes. Method: This study compared SJ performance across different knee angles—90º, 100º, 110º, 120º, 130º, and a self-selected depth—for jump height and other kinetic characteristics. For comparison between SJ and an unconstrained dynamic movement, participants also performed a countermovement jump from a self-selected depth. Thirteen participants (M_age = 25.4 ± 3.5 years, M_height = 1.8 ± 0.06 m, M_weight = 79.8 ± 9.5 kg) were recruited and tested for their SJ performance. Results: In the SJ, maximal jump height (35.4 ± 4.6 cm) was produced using a self-selected knee angle (98.7 ± 11.2°). Differences between 90°, 100°, and self-selected knee angles for jump height were trivial (ES ± 90% CL = 90°–100° 0.23 ± 0.12, 90°–SS ?0.04 ± 0.12, 100°–SS ?0.27 ± 0.20; 0.5–2.4 cm) and not statistically different. Differences between all other knee angles for jump height ranged from 3.8 ± 2.0 cm (mean ± 90% CL) to 16.6 ± 2.2 cm. A similar outcome to jump height was observed for velocity, force relative to body weight, and impulse for the assessed knee angles. Conclusions: For young physically active adult men, the use of a self-selected depth in the SJ results in optimal performance and has only a trivial difference to a constrained knee angle of either 90° or 100°.     

从膝角看不同水平男子跳远运动员摆动腿技术

主要从运动学的角度出发,着重从摆动腿膝关节角度的变化特点来分析不同水平男子跳远运动员起跳过程中摆动腿技术的异同,高水平运动员,在最后一步摆动腿蹬离地面瞬间,表现出相对较小的摆动腿膝关节角,角度变化曲线上表现为角度峰值出现在离地后0.02~0.03秒左右的瞬间,不同水平男子跳远运动员在起跳腿着地、起跳腿膝最大屈、起跳离地3个特征时刻,摆动腿膝关节角度差异不明显。     

The Effect of Depth Jumps and Weight Training on Leg Strength and Vertical Jump

Abstract

In recent years, a method of plyometrics (exercises that cause a rapid lengthening of a muscle prior to contraction) called depth jumping has become a part of the training routine of many athletes. Two experiments are described in which the effectiveness of the exercises is examined. In Experiment 1, undergraduate students in beginning weight training classes trained with three different jumping programs: (1) maximum vertical jumps, (2) 0.3 m depth jumps, and (3) 0.75 m and 1.10 m depth jumps. In addition, all groups also lifted weights. In Experiment 2, a weight training class and the volleyball team at Brigham Young University-Hawaii were divided into two groups. One group lifted weights and performed 0.75 and 1.10 m depth jumps. The other group only lifted weights. In Experiment 1, the three training programs resulted in increases in one repetition maximum (1 RM) squat strength, isometric knee extension strength, and in vertical jump; however, there were no significant differences between treatments. In Experiment 2, all groups made significant increases in vertical jump, except the group of weight lifters, who did no jumping. It was concluded that depth jumps are effective but not more effective than a regular jumping routine.     

Effect of Hand Spacing and Rear Knee Angle on the Sprinter's Start

Abstract

Twelve male subjects with no specialized training in sprint running were used to study effects upon the sprinter's start when hand spacing and rear knee angle were systematically altered. Results indicated that hand spacing had an effect on the start during the first 10 yd. of the sprint. The effect of rear knee angle was present at 10 yd. and the advantage gained at 10 yd. was still present at 30 yd.     

Muscle Fiber Type Composition and Knee Extension Isometric Strength Fatigue Patterns in Power- and Endurance-Trained Males

Abstract

Muscle fiber type composition in the vastus lateralis and knee extension isometric strength fatigue patterns were assessed in eight endurance-trained and eight power-trained males. Two different 25-trial isometric contraction exercise regimens were administered: a 10-second contraction, 5-second intertrial rest condition designed to induce a fast rate of fatigue and a 10-second contraction, 20-second intertrial rest condition designed to induce a slower rate of fatigue. The power group fatigued almost four times faster than the endurance group in the 10:5 exercise condition. In the 10:20 exercise condition, the endurance group showed no fatigue pattern while the power group had a significant strength decrement of 32%. In both exercise conditions, the power group exhibited more complex fatigue patterns in terms of statistically significant trend components. Maximum isometric strength correlated positively with slow twitch (ST) percent number in power (r = .80) and endurance (r = .48) groups, but negatively with linear trend coefficients in endurance (r = -.62) and power (r = -.80) groups. Maximum isometric strength also correlated higher with fatigue curve trend coefficients than did muscle fiber type composition. Thus, a faster rate of fatigue was associated with higher maximum isometric strength and with higher ST percent number and area. Since maximum isometric strength correlated with body weight (r = .86 for groups combined), both maximum isometric strength and muscle mass appear to be more important determinants of knee extension isometric strength fatigue patterns than muscle fiber type composition.     

浅析下肢肌力与侧举腿立踵平衡动作的关系

运用等速测试系统(MERAC)对20名不同等级水平的艺术体操运动员进行了下肢肌力方面的测试。结果表明1)主力腿踝关节前、后肌群应均衡发展、协同用力，为平衡动作的顺利完成打下坚实的基础；2)动力腿的肌力不需要很大，只要具备稍大于动力腿重力矩的那部分肌力即可。     

等速运动技术对膝关节损伤后肌力训练的影响研究

目的:评价等速运动技术在运动创伤中的应用价值,为运动创伤的功能康复提供有效的方法。方法:用Cybex-6000型等速肌力测试系统测试我院民族传统体育17例单侧膝关节损伤学生的肌肉功能。结果:患侧的各项肌肉功能指标均较健侧明显降低;而使用等速运动训练能较好地恢复损伤膝关节的肌肉功能。结论:等速肌肉测试技术是1种全新的肌肉功能评价方法,可提供可靠的量化指标和有效的训练方法。     

发展男子篮球运动员下肢速度力量的调查

依据当今速度力量研究的成果，制定专家、教练问卷，以河南和湖北几所高校篮球教研室为调查对象，针对男子篮球运动员下肢速度力量的训练方法做出综合统计分析，以期为篮球科学教学与训练提供参考。     

健康儿童膝关节屈伸肌力的等速测试研究

采用实验法对58名健康儿童进行膝关节屈伸肌测试。等速测试采用了3种测试速度。结果表明:3种不同测试速度中,在低速测试中峰力矩值最大,高速测试中峰力矩值最小,儿子童膝关节峰值力矩下降趋势与成年人一致。左右侧峰值力矩比较结果与成人相反,左侧大于右侧。屈伸峰值力矩的比例F/E>0.7,与国内外对成人的研究不一致,与优秀运动员比值相一致。男女儿童低速和中速的测试中没有性别差异,高速测试中有显著性差异。     

关于短跑后蹬角度若干问题的探讨

后蹬力是短跑主要的动力来源，是推动人体前进的基本条件。决定跑速的主要因素是步长与步频。然而后蹬角度的大小，对后蹬力的利用率，对步长与步频都将产生影响。后蹬角度大，对后蹬力的利用率、对步长与步频都会起消极的作用。本文主要对如何减小后蹬角度，以利于改进短跑技术，提高短跑运动成绩作一些探讨。     

对武术套路运动员腿部力量最佳训练手段的探索

运用问卷调查、观察和实验、模糊数学理论和模糊相关分析等研究方法,初步探讨武术套路运动员腿部力量最佳训练手段,为腿部力量训练提出理论依据和定量数据。     

我国花样滑冰优秀运动员膝关节力量研究

通过测试我国优秀花样滑冰运动员等速状态下膝关节屈肌群与伸肌群力量,对我国优秀花样滑冰运动员膝关节力量状况进行研究,结果：在60°/s等速测试中,我国优秀花样滑冰运动员相对最大峰力矩均值左侧膝关节屈肌为1.51 N·m/kg,伸肌为2.44 N·m/kg,右侧为1.54 N·m/kg和2.70N·m/kg;左侧膝关节屈肌群与伸肌群力矩比为62.02%,右侧为57.49%;膝关节左侧屈肌群与右侧屈肌群比值的均值为99.60%;左侧伸肌群与右侧伸肌群比值的均值为91.77%;差异均未出现显著性（P〉0.5）。结论：1）总体上说我国优秀花样滑冰运动员双膝力量未存在显著性差异;2）就单个运动员而言,我国优秀花样滑冰运动员双膝力量存在一定差异;3）我国优秀花样滑冰运动员膝关节屈肌群力量有待增强。     

不稳定训练对膝关节本体感觉和核心力量的影响

本研究的目的是检测10周不稳定训练项目对关节本体感觉的影响.测试参与者训练前、训练后躯干拉伸、弯屈力量和膝关节本体感觉.43名参加者进行了10周(每周3天)不稳定的训练项目,用瑞士球和体重作为对抗,17人是对照组成员.受训组训练前后增加躯干拉伸的力矩/体重的峰值(23.6%)和总功(20.1%),相反对照组分别减少了6.8%和6.7%.关节本体感觉(包括左右关节复位)训练前后提高44.7%(p=0.0006)以及训练以后的9个月提高了(21.5%).此外,右膝关节位置感在9个月时有一方面影响,比右膝关节在测试前偏离参照角度减少32.1%(P=0.03).一项用瑞士球和体重作为对抗的不稳定训练计划能对事先未经过训练的个体的关节本体感觉和核心力量提供长期的改善,证明这种新的压力训练将会对健康有益.     

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。     

青少年男子短跑运动员膝关节等速肌力特征研究

目的：通过对36名二级青少年男子短跑运动员双侧膝关节进行等速测试，探析青少年短跑运动员膝关节向心屈伸肌群的生物力学特性．为运动训练、科学选材及临床康复等提供理论依据。方法：利用Kinitech等速康复肌力测试系统对青少年男子短跑运动员膝关节屈伸肌群进行等速测试。结果：青少年男子短跑运动员双侧膝关节屈伸峰力矩随测试速度的增加呈递减趋势，且膝伸肌大于膝屈肌（P〈0．05），峰力矩屈伸比（V／E）随给定测试速度的增加呈递增趋势；最大功率随测试速度的增大而增加，同一测试速度下屈、伸肌群最大功率无明显差异，左、右侧相比也无显著性差异（600／s伸肌除外）；屈伸肌群达峰力矩的角度（APT）表现为伸肌角度明显低于屈肌角度，随速度增加左右两侧膝关节达峰力矩的角度无显著差异：双侧膝关节屈伸肌群达峰力矩的时间（TPT）随测试速度的增加而减小，同一测试速度下伸肌达峰力矩的时间大于屈肌；右侧膝关节屈肌相对峰力矩（PT／BM）与下肢形态学指标表现出不同程度的正相关。结论：青少年男子短跑运动员膝关节峰力矩变化规律与成年人相一致，但左右侧膝关节屈伸肌群做功能力发展不平衡，屈伸肌群运动达峰力矩角度、达峰力矩的时间存在显著差异。     

以运动学为视角分析核心力量训练对男子跳高运动员助跑最后一步和起跳阶段摆动腿的积极影响

本文以广州体育学院田径队5名男子运动员为研究对象,进行20周的核心力量训练,通过三维摄影对实验前后跳高运动员在助跑最后一步和起跳阶段摆动腿的支撑与摆动技术的运动学特征进行分析发现：起跳腿着地时摆动腿摆动的角速度、起跳蹬伸阶段摆动腿最大角速度及身体重心水平速度增加值等差异显著。     

急性力量训练对不同程度肥胖男大学生血清激素反应的影响

目的 研究急性力量训练对肥胖者血清Ghrelin、GH、Cortisol和Insulin水平的影响,探讨肥胖度对力量训练诱导Ghrelin与Cortisol反应的影响;方法:20名健康男大学生,按不同BMI分为3组,对照组(CG,n=7,BMI＜ 25.0),Ⅰ度肥胖组(ⅠFG,n=7,BMI为25.0～29.9),Ⅱ度肥胖组(ⅡFG,n=6,BMI＞ 30),进行约为80％1RM的急性力量训练后,采用ELISA法检测训练前、训练中、训练后即刻,30 min,60 min和120 min静脉血Ghrelin、GH、Cortisol和Insulin水平;结果:急性力量训练对各组GH、Cortisol和Insulin水平产生了显著影响;ⅡFG受试者Ghrelin水平显著高于CG(P＜0.05);CG(r=-0.507,P=0.034)与ⅠFG(r=-0.213,P=0.041)血清Ghrelin与GH的AUC呈负相关;ⅡFG受试者Ghrelin与Cortisol的AUC呈显著负相关(r=-0.63,P=0.038);结论:肥胖度的增加可能进一步改变糖代谢调节,进而影响肥胖者Ghrelin与Cortisol对急性力量训练的反应.