Abstract：
The effectiveness of isometric conditioning activity (CA) is not well described in terms of the level of performance enhancement and the presence of a stretch and shortening cycle in subsequent explosive tasks. Therefore, the aim of this study was to evaluate the effect of a maximum isometric squat as the CA and a subsequent squat jump (SJ) and countermovement jump (CMJ) height. A total of 31 semi-professional handball and soccer players were randomly assigned to two different conditions: (i) 3 sets of 3 repetitions (each lasting 3 s) of maximum isometric back squats (EXP), and (ii) no CA (CTRL). The jump height measurements were performed 5 min before the CA and approximately at the 4th and 8th minute following the completion of the CA. Due to the high inter-individual variability in the potentiation responses, the best value obtained post-CA was also analyzed. The SJ height significantly increased from baseline to the 8th minute post-CA (p = 0.004; ES = 0.31; Δ = +3.1 ± 5.0%) in the EXP condition. On the other hand, the CMJ height was significantly higher in the 4th (p = 0.001; ES = 0.23; Δ = +2.7 ± 3.7%) and 8th minute post-CA (p = 0.005; ES = 0.32; Δ = +3.6 ± 5.7%) in comparison to baseline during the EXP condition. Furthermore, SJ height significantly increased from baseline to the best time-point during the EXP (p < 0.001; ES = 0.47; Δ = +4.9 ± 4.9%) and CTRL (p = 0.038; ES = 0.21; Δ = +2.5 ± 5.8%) condition. Moreover, the CMJ height was significantly higher at the best time-points than at the baseline during EXP (p < 0.001; ES = 0.53; Δ = +5.6 ± 4.7%) and CTRL (p = 0.002; ES = 0.38; Δ = +3.1 ± 5.2%) condition. The findings from this study indicate that a maximum isometric squat, used as a CA, effectively improved SJ and CMJ height. This suggests that the presence or absence of a stretch and shortening cycle in both CA and post-CA tasks does not significantly impact the post-activation performance enhancement response.
摘要：
等距调节活动（CA）的有效性在性能增强水平以及后续爆炸性任务中的拉伸和缩短周期的存在方面没有得到很好的描述。因此,这项研究的目的是评估最大等距下蹲对CA以及随后的下蹲跳跃（SJ）和反运动跳跃（CMJ）高度的影响。总共31名半职业手球和足球运动员被随机分配到两种不同的条件下：（i）3组3次重复（每次持续3s）的最大等距后深蹲（EXP），和(ii)无CA(CTRL)。跳跃高度测量在CA前5分钟和大约在CA完成后的第4和第8分钟进行。由于增强反应的个体间高度变异性，还分析了CA后获得的最佳值.在EXP条件下,SJ高度从基线到CA后第8分钟显著增加(p=0.004;ES=0.31;Δ=+3.1±5.0%)。另一方面,与EXP条件下的基线相比，CA后第4分钟（p=0.001；ES=0.23；Δ=2.7±3.7％）和第8分钟（p=0.005；ES=0.32；Δ=3.6±5.7％）的CMJ高度显着高于基线。此外，在EXP(p<0.001;ES=0.47;Δ=+4.9±4.9%)和CTRL(p=0.038;ES=0.21;Δ=+2.5±5.8%)期间,SJ高度从基线到最佳时间点显著增加。此外，在EXP(p<0.001;ES=0.53;Δ=+5.6±4.7%)和CTRL(p=0.002;ES=0.38;Δ=+3.1±5.2%)期间,最佳时间点的CMJ高度显著高于基线。这项研究的结果表明，最大的等距深蹲，用作CA，有效提高了SJ和CMJ的高度。这表明CA和CA后任务中是否存在拉伸和缩短周期不会显着影响激活后性能增强响应。
