Data

This randomized controlled trial investigated the effects of an 8-week, volume-equated eccentric training program comprising Nordic Hamstring and Reverse Nordic exercises performed either once or twice per week on physical fitness measures in pubertal male soccer players. A total of 34 participants were randomly assigned into a 1-day (n = 16; age = 14.58 ± 0.28 years) or 2-day (n = 18; age = 14.84 ± 0.22 years) per week training group. Physical fitness was assessed using 5 m and 10 m sprints, the 505 change of direction (CoD) speed test, Y-shaped agility test, countermovement jump (CMJ), and standing long jump (SLJ). Significant group-by-time interactions were observed for the 505 CoD test, agility, and CMJ performance (effect sizes [ES] = 0.80 to 1.13). However, no significant interactions were found for the 5 and 10 m sprint as well as SLJ (p > 0.05). Compared to the 1-day group, the 2-day training group showed greater improvements in CoD speed (∆7.36%; p < 0.001; ES = 0.92), agility (∆7.91%; p < 0.001; ES = 1.68), and CMJ (∆7.44%; p < 0.01; ES = 0.35), while no differences were observed in 5, and 10 m linear sprint or SLJ performance. According to individual response analysis, improvements across the physical fitness parameters beyond the smallest worthwhile change (SWC0.2) were observed in 22–83% of players in the 1-day group and 77–100% in the 2-day group. In summary, the findings suggest that when training volume is matched, distributing the eccentric training regimen over two days per week may lead to greater improvements in CoD speed, agility, and CMJ performance compared to a single-day approach.

本随机对照试验探究了为期8周、负荷量匹配的离心训练方案对青春期男性足球运动员身体素质指标的影响，该方案包含北欧腘绳肌（Nordic Hamstring）训练与反向北欧（Reverse Nordic）训练，每周实施1次或2次。共计34名受试者被随机分配至每周1次训练组（n=16；年龄=14.58±0.28岁）与每周2次训练组（n=18；年龄=14.84±0.22岁）。
采用5米、10米短跑，505变向（change of direction, CoD）速度测试，Y型敏捷性测试，反向跳跃（countermovement jump, CMJ）测试以及立定跳远（standing long jump, SLJ）评估受试者身体素质。研究观察到505变向速度测试、敏捷性与反向跳跃表现存在显著的组×时间交互效应（效应量[ES]=0.80~1.13）。但5米、10米短跑及立定跳远表现未出现显著交互效应（p>0.05）。
与每周1次训练组相比，每周2次训练组的变向速度（提升幅度Δ7.36%；p<0.001；ES=0.92）、敏捷性（Δ7.91%；p<0.001；ES=1.68）及反向跳跃表现（Δ7.44%；p<0.01；ES=0.35）提升幅度更显著，而两组在5米、10米直线短跑及立定跳远表现上无显著差异。
经个体应答分析，达到最小有意义变化值（smallest worthwhile change, SWC=0.2）以上的身体素质参数改善率在每周1次训练组中为22%~83%，在每周2次训练组中为77%~100%。
综上，本研究结果表明，在训练负荷量匹配的前提下，将离心训练计划分散至每周2次完成，相较每周1次的训练方案，可更显著提升受试者的变向速度、敏捷性及反向跳跃表现。