The anthropometric data of participants.

Background
The principle of gradual overload is crucial in improving sports performance, yet the effects of combining speed and weight overloads in plyometric training remain understudied.
Objective
This study investigated the effects of plyometric training with speed and weight overloads on isokinetic strength, explosive power, and agility in volleyball players.
Method
Forty male volleyball players were randomly assigned to four groups: plyometric training (PT), plyometric training with speed overload (PTS), plyometric training with weight overload (PTW), and plyometric training with both speed and weight overload (PTSW). Each group completed a four-week plyometric training regimen. Performance metrics, including Sarjent’s jump height (SJH), Spike jump height (SPJH), Sheppard test (ShT), muscle voluntary isometric contraction (MVIC), rate of force development (RFD), absolute peak torque (PTQ), relative peak torque (RPT), and average power (AP) of knee extensors and flexors were measured before and after the intervention.
Results
SJH improved significantly in PTS (P = 0.012), PTW (P = 0.041), and PTSW (P = 0.001) compared to PT. SPJH showed substantial gains in PTS (P = 0.002), PTW (P = 0.001), and PTSW (P = 0.001) compared to PT. Average jump height and highest jump in ShT were also significantly higher in PTS, PTW, and PTSW (P < 0.05). Additionally, RFDext240°/s was enhanced considerably in PTS (P = 0.001) and PTSW (P = 0.001).
Conclusion
Based on the results, plyometric training with speed and weight overloads (PTSW) demonstrated superior enhancements in isokinetic strength, explosive power, and jumping performance. This combined approach is highly effective and significantly benefits male volleyball players, aiming to enhance their physical abilities.

研究背景
渐进超负荷原则（principle of gradual overload）对于提升运动表现至关重要，但在超等长训练（plyometric training）中结合速度超负荷与重量超负荷的组合训练效果仍有待深入探究。

研究目标
本研究旨在探究结合速度与重量超负荷的超等长训练，对排球运动员等速肌力（isokinetic strength）、爆发力（explosive power）以及敏捷性（agility）的影响。

研究方法
将40名男性排球运动员随机分为四组：超等长训练组（PT）、速度超负荷超等长训练组（PTS）、重量超负荷超等长训练组（PTW）以及同时结合速度与重量超负荷的超等长训练组（PTSW）。所有组别均完成为期四周的超等长训练方案。于干预前后测量多项运动表现指标，包括萨金特跳高度（Sarjent’s jump height，SJH）、扣球跳高度（Spike jump height，SPJH）、谢泼德测试（Sheppard test，ShT）、肌肉自主等长收缩（muscle voluntary isometric contraction，MVIC）、力量发展速率（rate of force development，RFD）、膝伸肌与屈肌的绝对峰值扭矩（absolute peak torque，PTQ）、相对峰值扭矩（relative peak torque，RPT）以及平均功率（average power，AP）。

研究结果
相较于超等长训练组（PT），速度超负荷超等长训练组（PTS，P=0.012）、重量超负荷超等长训练组（PTW，P=0.041）与联合超负荷超等长训练组（PTSW，P=0.001）的萨金特跳高度均获得显著提升。扣球跳高度在PTS组（P=0.002）、PTW组（P=0.001）与PTSW组（P=0.001）中均出现显著提升。谢泼德测试中的平均跳高度与最高跳高度，在PTS、PTW与PTSW组中也显著高于PT组（P<0.05）。此外，240°/s角速度下的伸肌力量发展速率（RFDext240°/s）在PTS组（P=0.001）与PTSW组（P=0.001）中得到显著增强。

研究结论
基于上述实验结果，同时结合速度与重量超负荷的超等长训练（PTSW）在等速肌力、爆发力与跳跃表现方面展现出更优异的提升效果。该联合训练方案成效显著，可有效助力男性排球运动员提升身体素质。