Effect of pedaling speed and load on EMG activity of biarticular muscles in thigh portion

本研究的目的是检查的影响骑车速度和负载的EMG活动biarticular大腿部分的肌肉,和clariy EMG活动的特点与“力量”和“速度型”的输出功率。研究要求11名大学生在功率输出为2.5、3.5、4.5、5.5和6.5W/kg的情况下，以恒定的踏板速度（60rpm）和不同的踏板速度（50、70、90、110和130rpm）进行自行车测力仪运动。在每次蹬车运动中，记录右股外侧肌、股直肌、股短二头肌和股长二头肌的肌表肌电活动，并要求受试者分别在体重的5、7.5、10和12.5%负荷下进行4次超极限蹬车运动，持续8秒，测量其最大无氧能量输出，然后根据其能量输出特征将其分为力量型和速度型两组。随着蹬车速度和负荷的增加，所有肌肉的IEMG/秒呈线性增加。单关节肌的IEMG/W kg^<-1>随蹬力的增加而降低，双关节肌的IEMG/W kg^<-1>不变。另一方面，踏板速度增加导致双关节肌IEMG/W kg^<-1>下降，单关节肌IEMG活动无变化。然而，在肌电活动中发现的这些趋势依赖于输出功率的类型。速度型组股骨直肌和股二头肌IEMG/W kg^<-1>随蹬踏速度的增加而降低。由此可见，增加蹬车速度可以抑制大腿部分双关节肌的活动，而股直肌和股二头肌的活动可能负责无氧动力输出速度型的发展。

The purpose of this study was to examine the effect of pedaling speed and load on EMG activity of biarticular muscles in thigh portion, and to clariy the characteristics of EMG activity in relation to "strength type" and "speed type" of power output. Eleven collegiate men were asked to perform bicycle ergometer exercise at power outputs of 2.5, 3.5, 4.5, 5.5 and 6.5W/kg by constant pedaling speed (60rpm) and various pedaling speed (50, 70, 90, 110 and 130rpm) . During each pedaling exercise, surface EMG activities were recorded from right M.vastus lateralis, rectus femoris, biceps femoris caput breve and biceps femoris caput longum, The subjects were also asked to perform 4 supramaximal pedaling exercsie at loads of 5, 7.5, 10, and 12.5% of their body weight for 8sec to measure their maximal anaerobic power output and then they were classified into strength type or speed type group in relation to their power output characteristics. By increasing pedaling speed and load, IEMG/sec in all muscles studied were increased linealy. IEMG/W kg^<-1> of single articular muscles was decreased with incresing pedaling torque, but that of biarticular muscles was unchanged. On the other hand, increase of pedaling speed induced the decrease of IEMG/W kg^<-1> in biarticular muscles and no change in IEMG activities of sigle articular muscles. However, these tendency found in EMG activities were dependent on the type for power output. In speed type group, it was showed that IEMG/W kg^<-1> in M.rectus femoris and biceps femoris caput breve were decreased with increasing pedaling speed. From these results, it was suggested that by increasing pedaling speed, activity of biarticular muscles of thigh portion could be inhibited, and activities of rectus femoris and biceps femoris caput breve woud be responsible for development of speed type for anaerobic power output.