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

本研究的目的是研究踏板速度和负荷对大腿部分双关节肌肌电活动的影响，并阐明肌电活动与功率输出的“力量型”和“速度型”之间的关系。11名大学生被要求在2.5、3.5、4.5、5.5和6.5W/kg的功率输出下进行自行车功率计运动，分别以恒定的踏板速度(60rpm)和不同的踏板速度(50、70、90、110和130rpm)进行。在每次踏板运动中，记录受试者右侧股外侧肌、股直肌、股二头肌短头肌和股二头肌长头肌的表面肌电信号活动，并要求受试者在5、7.5、10和12.5%体重的负荷下进行4次超大负荷踏板运动，持续8s，测量其最大无氧功率输出，并根据功率输出特性将受试者分为力量型组和速度型组。随着踏板速度和负荷的增加，所研究的所有肌肉的IEMG/s都呈线性增加。单关节肌的IEMG/W kg~(-1)~(-1)随着踏板扭矩的增大而降低，双关节肌的IEMG/W·kg~(-1)则无明显变化。而踏板速度的增加则导致双关节肌IEMG/W kg~(-1)的下降，而单关节肌的IEMG活动无明显变化。然而，在肌电活动中发现的这些趋势取决于功率输出的类型。在速度型组中，随着踏板速度的增加，股直肌和股二头肌的IEMG/W kg~(-1)和~(-1)GT；由此可见，通过提高踏板速度，可以抑制大腿部双关节肌的活动，股直肌和股二头肌短肌的活动可能是无氧输出速度型发展的主要原因。

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.