Li L, Caldwell G E
Biomechanics Laboratory, Department of Exercise Science, University of Massachusetts, Amherst, Amherst, Massachusetts 01003, USA.
J Appl Physiol (1985). 1998 Sep;85(3):927-34. doi: 10.1152/jappl.1998.85.3.927.
The purpose of the present study was to examine the neuromuscular modifications of cyclists to changes in grade and posture. Eight subjects were tested on a computerized ergometer under three conditions with the same work rate (250 W): pedaling on the level while seated, 8% uphill while seated, and 8% uphill while standing (ST). High-speed video was taken in conjunction with surface electromyography (EMG) of six lower extremity muscles. Results showed that rectus femoris, gluteus maximus (GM), and tibialis anterior had greater EMG magnitude in the ST condition. GM, rectus femoris, and the vastus lateralis demonstrated activity over a greater portion of the crank cycle in the ST condition. The muscle activities of gastrocnemius and biceps femoris did not exhibit profound differences among conditions. Overall, the change of cycling grade alone from 0 to 8% did not induce a significant change in neuromuscular coordination. However, the postural change from seated to ST pedaling at 8% uphill grade was accompanied by increased and/or prolonged muscle activity of hip and knee extensors. The observed EMG activity patterns were discussed with respect to lower extremity joint moments. Monoarticular extensor muscles (GM, vastus lateralis) demonstrated greater modifications in activity patterns with the change in posture compared with their biarticular counterparts. Furthermore, muscle coordination among antagonist pairs of mono- and biarticular muscles was altered in the ST condition; this finding provides support for the notion that muscles within these antagonist pairs have different functions.
本研究的目的是检验骑行者在坡度和姿势变化时的神经肌肉改变。八名受试者在计算机化测力计上，于三种条件下以相同工作负荷（250瓦）进行测试：坐着在平路上蹬踏、坐着上坡8%以及站立上坡8%（站立位）。在采集高速视频的同时，记录了下肢六块肌肉的表面肌电图（EMG）。结果显示，在站立位条件下，股直肌、臀大肌（GM）和胫骨前肌的肌电图幅度更大。在站立位条件下，臀大肌、股直肌和股外侧肌在曲柄周期的更大比例时间内表现出活动。腓肠肌和股二头肌的肌肉活动在不同条件下未表现出显著差异。总体而言，仅骑行坡度从0%变为8%并未引起神经肌肉协调性的显著变化。然而，在上坡8%时从坐着姿势变为站立位蹬踏伴随着髋部和膝部伸肌的肌肉活动增加和/或延长。针对下肢关节力矩对观察到的肌电图活动模式进行了讨论。与双关节肌相比，单关节伸肌（臀大肌、股外侧肌）在姿势改变时活动模式的变化更大。此外，在站立位条件下单关节肌和双关节肌的拮抗肌对之间的肌肉协调性发生了改变；这一发现为这些拮抗肌对中的肌肉具有不同功能这一观点提供了支持。
