Imposing a pause between the eccentric and concentric phases increases the reliability of isoinertial strength assessments

Abstract

This study analysed the effect of imposing a pause between the eccentric and concentric phases on the biological within-subject variation of velocity- and power–load isoinertial assessments. Seventeen resistance-trained athletes undertook a progressive loading test in the bench press (BP) and squat (SQ) exercises. Two trials at each load up to the one-repetition maximum (1RM) were performed using 2 techniques executed in random order: with (stop) and without (standard) a 2-s pause between the eccentric and concentric phases of each repetition. The stop technique resulted in a significantly lower coefficient of variation for the whole load–velocity relationship compared to the standard one, in both BP (2.9% vs. 4.1%; P = 0.02) and SQ (2.9% vs. 3.9%; P = 0.01). Test–retest intraclass correlation coefficients (ICCs) were r = 0.61–0.98 for the standard and r = 0.76–0.98 for the stop technique. Bland–Altman analysis showed that the error associated with the standard technique was 37.9% (BP) and 57.5% higher (SQ) than that associated with the stop technique. The biological within-subject variation is significantly reduced when a pause is imposed between the eccentric and concentric phases. Other relevant variables associated to the load–velocity and load–power relationships such as the contribution of the propulsive phase and the load that maximises power output remained basically unchanged.     

我国男子举重运动员拇指长度与抓举成绩关系初探

本文通过对多次获得世界冠军的刘寿斌、何英强等154名优秀运动员的调查,得知拇指长度与抓举成绩有关,并提出了男子举重运动员拇指长度的选材下限为(5.91-0.15)厘米。对男子抓举运动员的选材提供了参考依据。     

我国优秀男子举重运动员抓举技术结构研究

采用录像解析、动力测试、数理统计等方法 ,对我国优秀男子举重运动员抓举技术动作进行三维动力学和二维运动学测试分析 ,根据技术动作的用力特征和运动轨迹的定量描述 ,得出抓举技术结构特征和主要技术影响因素 ,指出抓举技术的主要生物力学因子。     

The effect of elevating the heels on spinal kinematics and kinetics during the back squat in trained and novice weight trainers

ABSTRACT

This research assessed the influence of various heel elevation conditions on spinal kinematic and kinetic data during loaded (25% and 50% of body weight) high-bar back squats. Ten novice (mass 67.6 ± 12.4 kg, height 1.73 ± 0.10 m) and ten regular weight trainers (mass 66.0 ± 10.7 kg, height 1.71 ± 0.09 m) completed eight repetitions at each load wearing conventional training shoes standing on the flat level floor (LF) and on an inclined board (EH). The regular weight training group performed an additional eight repetitions wearing weightlifting shoes (WS). Statistical parametric mapping (SPM1D) and repeated measures analysis of variance were used to assess differences in spinal curvature and kinetics across the shoe/floor conditions and loads. SPM1D analyses indicated that during the LF condition the novice weight trainers had greater moments around L4/L5 than the regular weight trainers during the last 20% of the lift (P < 0.05), with this difference becoming non-significant during the EH condition. This study indicates that from a perspective of spinal safety, it appears advantageous for novice weight trainers to perform back squats with their heels slightly elevated, while regular weight trainers appear to realize only limited benefits performing back squats with either EH or WS.     

Changing the stability conditions in a back squat: the effect on maximum load lifted and erector spinae muscle activity

The aim of this study was to identify how changes in the stability conditions of a back squat affect maximal loads lifted and erector spinae muscle activity. Fourteen male participants performed a Smith Machine (SM) squat, the most stable condition, a barbell back (BB) squat, and Tendo-destabilizing bar (TBB) squat, the least stable condition. A one repetition max (1-RM) was established in each squat condition, before electromyography (EMG) activity of the erector spinae was measured at 85% of 1-RM. Results indicated that the SM squat 1-RM load was significantly (p = 0.006) greater (10.9%) than the BB squat, but not greater than the TBB squat. EMG results indicated significantly greater (p < 0.05) muscle activation in the TBB condition compared to other conditions. The BB squat produced significantly greater (p = 0.036) EMG activity compared to the SM squat. A greater stability challenge applied to the torso seems to increase muscle activation. The maximum loads lifted in the most stable and unstable squats were similar. However, the lift with greater stability challenge required greatest muscle activation. The implications of this study may be important for training programmes; if coaches wish to challenge trunk stability, while their athletes lift maximal loads designed to increase strength.     

人杠重心运动轨迹在抓举技术分析中的运用简

通过采用三维录像解析法对4名四川省举重队抓举运动员的运动技术进行分析,选择人体重心和杠铃重心在垂直、前后、左右三个方向上的运动轨迹作为分析指标,利用指标中的数据变化特点来解读运动员在抓举技术中所需要遵循的“近”、“快”、“低”三原则.结果表明;人杠重心运动轨迹在抓举运动技术分析中不但可以直观准确地判断运动员技术的优缺点,还可以作为教练员指导训练的定量分析指标.     

递增负荷下短跑运动员全蹲时臀部肌肉与股二头肌表面肌电变化特征研究

运用表面肌电测试仪器,对部分短跑运动员递增负荷下全蹲训练进行测试,对所测表面肌电现象进行分析。测试结果:随着负荷的递增,股二头肌的IEMG随着负荷的递增而逐步增加,臀中肌、臀大肌IEMG、IEMG/S和RMS随负荷的增加而增大。股二头肌、臀中肌、臀大肌随着负荷的递增而最大振幅也逐步增大,振幅最大时的膝关节角度范围分别为:88.94~106.33°,101.345~121.667°,88.779~101.591°;平均角度分别为99.77°,113.157°,93.917°。     

从运动生物力学角度看抓举失败——以全国男子举重锦标赛江苏队员为例

通过立体摄像方法，从运动生物力学的角度，对成功和失败试举动作进行了对比分析。从中看出，对同一运动员尽管成功和失败抓过程中，杠铃重心都达到相同的最大高度，然而杠铃重心和人体重心的相对垂直距离是不一样的失败试举过程中，运动员没有获得足够的垂直支撑空间，在极限负荷情况下当然不能发挥出最大的支撑力量，造成失败。     

幼儿心功能测评方法的试验研究

为了确定幼儿心功能测评方法，选择了3种不同的运动负荷量，即“30 s30次蹲起”、“30 s20次蹲起”、“45 s30次蹲起”，对1412名3-6岁幼儿进行实验、对比发现，处于发育朗的幼儿不宜进行大强度负荷的运动实验，静态的心率、血压测评也难以对心血管功能作出有效的评定。因此，最终确定以“45s30次蹲起”的定量负荷测评作为该年龄阶段心功能评价科学、有效、简便易行的方法。     

女子抓举技术的生物力学特征

运用录像分析系统，分析了我国优秀女子举重运动员的抓举技术，对抓举技术中的预备、提铃、发力、下蹲支撑、上举等5个动作环节进行了阐述，揭示该技术的生物力学特征，为运动员教练员提供可靠的数据参考。