Familiarization,validity and smallest detectable difference of the isometric squat test in evaluating maximal strength

Isometric multi-joint tests are considered reliable and have strong relationships with 1RM performance. However, limited evidence is available for the isometric squat in terms of effects of familiarization and reliability. This study aimed to assess, the effect of familiarization, stability reliability, determine the smallest detectible difference, and the correlation of the isometric squat test with 1RM squat performance. Thirty-six strength-trained participants volunteered to take part in this study. Following three familiarization sessions, test–retest reliability was evaluated with a 48-hour window between each time point. Isometric squat peak, net and relative force were assessed. Results showed three familiarizations were required, isometric squat had a high level of stability reliability and smallest detectible difference of 11% for peak and relative force. Isometric strength at a knee angle of ninety degrees had a strong significant relationship with 1RM squat performance. In conclusion, the isometric squat is a valid test to assess multi-joint strength and can discriminate between strong and weak 1RM squat performance. Changes greater than 11% in peak and relative isometric squat performance should be considered as meaningful in participants who are familiar with the test.     

优秀举重运动员抓举技术的敏感指标分析

1研究目的 本研究主要通过抓举不同动作阶段杠铃上升时间比、高度比和作功比这3个敏感指标对近几届参加奥运会集训的优秀举重运动员的抓举技术进行研究,从而揭示优秀运动员抓举技术特征和男女选手在技术上的差异,为教练员科学训练提供一定的依据。     

基于“Plyometrics”理论的WCBA运动员力量训练

"Plyometrics"练习是一种把退让练习和克制练习结合在一起的训练方法,对提高运动员爆发力有着重要的作用,对运动员的基础力量也有要求.WCBA教练员对运动员的力量要求偏低;WCBA运动员无论是上肢的卧推,还是下肢的深蹲都不能达到"Plyometries"练习理论上的要求.在此力量的基础上,WCBA运动员应较多地进行"Upper Body Plyometrics"练习,有利于运动员爆发力和灵敏性的提高.对有下肢肌腱劳损的WCBA运动员,也可进行"Upper Body Plyometrics"练习,提高其爆发力.     

Performance characteristics of Parkour practitioners: Who are the traceurs?

Parkour is a modern physical activity that consists of using the environment, mostly urban, as a playground of obstacles. The aims of this study were (i) to investigate age, anthropometric and training characteristics of Parkour practitioners, called ‘traceurs’ and (ii) to assess jump performances and muscular characteristics of traceurs, compared to those of gymnasts and power athletes. The mean age of the population of traceurs studied (n?=?130) was 19.4?±?4.3 years, women represented 12.4% of the total field and mean training volume was 8.1?±?0.5?hours/week. Vertical and long jump performances were analysed on smaller samples of participants (four groups, n?=?15 per group); and eccentric (?90°?s^?1, ?30°?s^?1), concentric (30°?s^?1, 90°?s^?1) and isometric knee extensors torques were evaluated by means of an isokinetic dynamometer. Traceurs showed greater (P?P?P?P?相似文献   

Biomechanical mechanisms of jumping performance in youth elite female soccer players

ABSTRACT

We aimed to determine key biomechanical parameters explaining age-related jumping performance differences in youth elite female soccer players. Multiple biomechanical parameters from countermovement (CMJ) squat (SJ) and drop (DJ) jump testing of elite female soccer players (n = 60) within the same national training centre were analysed across ages 9-11y, 12-14y and 15-19y. Effects of age group and jump type on jump height were found, with the older jumping higher than the younger groups in all jumps (P < 0.05). For DJ, higher reactive strength index was found for older, compared to each younger group (P < 0.001). For CMJ and SJ, peak power was the most decisive characteristic, with significant differences between each group for absolute peak power (P < 0.0001) and body-weight-normalised peak power in CMJ (57 ± 7W/kg, 50 ± 7W/kg, 44.7 ± 5.5W/kg; P < 0.05) and between the older and each younger group in SJ (56.7 ± 7.1W/kg, 48.9 ± 7.1W/kg, 44.6 ± 6W/kg; P < 0.01). Age-related differences in jumping performance in youth elite female soccer players appear to be due to power production during standing jumps and by the ability to jump with shorter ground contact times during reactive jumps.     

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°.     

Force– and power–time curve comparison during jumping between strength-matched male and female basketball players

The purpose of this study was to compare force– and power–time curve variables during jumping between Division I strength-matched male and female basketball athletes. Males (n?=?8) and females (n?=?8) were strength matched by testing a one-repetition maximum (1RM) back squat. 1RM back squat values were normalised to body mass in order to demonstrate that strength differences were a function of body mass alone. Subjects performed three countermovement jumps (CMJ) at maximal effort. Absolute and relative force– and power–time curve variables from the CMJs were analysed between males and females. Average force– and power–time curves were generated for all subjects. Jump height was significantly greater (p?≤?.05) in males than females. Absolute force was higher in males during the concentric phase, but not significantly different (p?≥?.05) when normalised to body mass. Significance was found in absolute concentric impulse between sexes, but not when analysed relative to body mass. Rate of force development, rate of power development, relative peak force, and work were not significantly different between sexes. Males had significantly greater impulse during the eccentric phase as well as peak power (PP) during the concentric phase of the CMJ than did females in both absolute and relative terms. It is concluded that sex differences are not a determining factor in measured force during a CMJ when normalised to body mass between strength-matched subjects. However, eccentric phase impulse and concentric phase PP appear to be influenced by sex differences independent of matching strength levels.     

浅析挺举过程中的下蹲翻技术

本文通过对举重运动相关书籍的反复学习和研究,结合本人近30年举重教学的经验,以及对2009年全国男子举重锦标赛部分运动员（其中：奥运冠军3名、世界冠军5名、亚洲冠军4名、全国冠军22名、全国前3名18名、全国前8名35名）的访问、调查和相关数据的分析,对下蹲翻技术进行了较为全面而细致的陈述和分析。至今为止,这是全国少有对＂下蹲翻＂技术进行细致、全面研究的文章。它对我国挺举成绩的提高、举重教学有一定的积极意义和参考价值。     

振动负荷辅助举重训练对优秀女子举重运动员影响的实验研究

目的:配合奥运科技攻关冬训备战任务(即提高优秀女子举重运动员腿部力量以及躯干支撑能力).方法:采用自制振动台对6名国家队优秀女子举重运动员实施振动负荷辅助训练,通过机体运动能力(即后深蹲、预蹲和膝、髋关节等速肌力矩)、身体形态指标测试记录并进行分析讨论.结果:优秀女子举重运动员通过振动负荷辅助训练后后深蹲和预蹲单位体重增加7%以上,膝、髋关节单位体重肌力矩增加10%～16%左右.身体形态指标显示出体重变化在1 kg之内,体脂没有变化,局部围度变化在1 cm左右,3项形态指标变化在正常范围,对比赛和训练没有影响.振动负荷是交变负荷的一种,振动负荷从属于交变负荷.研究认为,中等强度的振动负荷辅助训练可以提高局部关节周围肌腱及深层次肌肉功能,导致关节以及肌肉力量和张力发展平衡,提高了相对较弱肌群力量水平,促进机体整体机能提高.振动负荷对身体形态影响的机制探讨中得出低频振动,提高肌肉的新陈代谢能力,促进血液循环.结论:优秀女子举重运动员通过振动负荷辅助训练后,身体局部及整体肌群协调性得到提高,腿部肌群力量有明显突破,躯干支撑能力明显加大.振动负荷辅助训练前后,实验对象的身体形态变化不大,不会影响比赛和训练.振动负荷辅助训练使得训练有素的机体整体能力突破的可能机制为振动刺激对机体中、深层次肌群产生由小到大的交变刺激效应,以及振动显著减少了流体的内摩擦系数,增加了其流动性.     

举重运动员抓举动作脊柱腰椎节段受力特点分析 ———基于有限元理论

利用CT扫描数据建立具有高度几何材料相似性的腰椎运动节段(L1-L2)的三维有限元模型,分析举重运动员抓举完全起立阶段脊柱腰椎节段生物力学特性,以便对举重运动员腰部损伤进行积极的预防,减少伤病的发生.结果表明:在举重运动员抓举完全起立姿态下,其椎体主要的应力分布在小关节和椎弓根处,椎间盘接触压力主要集中在纤维环中后部,位移主要集中在椎间盘的后外侧;此时,如果杠铃的重量过大,运动员腰部力量不足,引起腰椎关节失稳,会造成椎间盘过分挤压,且在重力的作用下峡部向前剪切力过大可引起峡部裂伤.本研究所建立的腰椎L1-L2节段的三维有限元模型足重要的脊柱生物力学研究平台,可应用于众多相关研究领域.