Magnus Charlene R A, Farthing Jonathan P
College of Kinesiology, University of Saskatchewan, Saskatoon, Canada.
Appl Physiol Nutr Metab. 2008 Dec;33(6):1132-9. doi: 10.1139/H08-101.
Bilateral deficit is defined as the difference in the summed force between contracting muscles alone and contracting contralateral homologous muscles in combination. The purpose of the study was to investigate how postural stability influences bilateral deficit by comparing an exercise requiring more postural stability (the leg press) with an exercise requiring less postural stability (the handgrip). Eight participants volunteered for the study (3 males, 5 females). Maximal strength was determined by a 1-repetition maximum for the leg press (weight machine) and handgrip (dynamometer) exercises. Electromyography was used to measure activation of the effectors (flexor carpi ulnaris for the handgrip and vastus lateralis for the leg press) and the core muscles (rectus abdominis and external obliques). Bilateral deficit was greater in the leg press (-12.08 +/- 10.22%) than the handgrip (-0.677 +/- 5.00%; p < 0.05). Muscle activation of the effectors and core muscles was not significantly different between unilateral and bilateral conditions for either exercise. However, core muscle activation was significantly greater during the leg press (48.30 +/- 19.60 microV) than during the handgrip (16.50 +/- 8.10 microV; p < 0.05) exercise. These results support the hypothesis that an exercise requiring more postural stability (e.g., the leg press) will have a larger deficit and greater activation of core muscles than an exercise requiring less postural stability (e.g., the handgrip). Since the bilateral deficit was only apparent for the leg press exercise, we conclude that postural stability requirements might influence the magnitude of bilateral deficit.
双侧 deficit 定义为仅收缩肌肉时的总力量与同时收缩对侧同源肌肉时的总力量之差。本研究的目的是通过比较一项需要更多姿势稳定性的运动（腿举）和一项需要较少姿势稳定性的运动（握力），来研究姿势稳定性如何影响双侧 deficit。八名参与者自愿参加了这项研究（3 名男性，5 名女性）。通过腿举（重量训练器）和握力（测力计）练习的 1 次重复最大值来确定最大力量。使用肌电图来测量效应器（握力时的尺侧腕屈肌和腿举时的股外侧肌）和核心肌肉（腹直肌和腹外斜肌）的激活情况。腿举时的双侧 deficit（-12.08±10.22%）大于握力时的双侧 deficit（-0.677±5.00%；p<0.05）。对于这两项运动中的任何一项，效应器和核心肌肉的肌肉激活在单侧和双侧条件下均无显著差异。然而，腿举运动期间的核心肌肉激活（48.30±19.60 μV）显著大于握力运动期间的核心肌肉激活（16.50±8.10 μV；p<0.05）。这些结果支持了这样一个假设，即一项需要更多姿势稳定性的运动（例如腿举）比一项需要较少姿势稳定性的运动（例如握力）将具有更大的 deficit 和更大的核心肌肉激活。由于双侧 deficit 仅在腿举运动中明显，我们得出结论，姿势稳定性要求可能会影响双侧 deficit 的大小。
