30秒全力蹬踏自行车运动中下肢肌肉协同活动特征研究

Research on Coordination of Lower Limb Muscles during 30-second All-out Sprint Cycling Exercise

目的:观察30秒全力蹬踏自行车运动中下肢肌肉表面肌电信号随运动时间变化的特征,揭示该运动过程中下肢主要用力肌肉的协同活动规律。方法:10名场地自行车运动员(男7名,女3名,年龄21.5±4.7岁)在Wattbike功率自行车上进行30秒全力蹬踏自行车运动,记录输出功率、蹬踏频率和下肢股直肌、股肌(股内侧肌、股外侧肌)、腘绳肌(股二头肌、半腱肌)、胫骨前肌、腓肠肌外侧头、比目鱼肌的表面肌电信号,并采用高速摄像机记录运动影像。基于运动影像确定蹬踏周期起止点。基于表面肌电信号获取各测试肌肉的肌电中值频率、活动水平、激活时间和三组肌肉的协同收缩比率(CAI胫骨前肌/比目鱼肌、CAI股肌/腓肠肌、CAI股肌/腘绳肌)。结果:在运动结束即刻,蹬踏频率和输出功率分别相对于最大值下降了21.51%±5.40%和56.17%±9.91%。股直肌、股肌、腓肠肌肌电幅值、激活时间和肌电中值频率随运动持续时间的增加表现出单调递减(P<0.05)。肌肉协同收缩比率CAI胫骨前肌/比目鱼肌随运动持续时间的增加单调递增,而协同收缩比率CAI股肌/腓肠肌表现出单调递减趋势(P<0.05)。结论:在30秒全力蹬踏自行车运动中,股直肌、股肌、胫骨前肌、腓肠肌都出现较深的肌肉疲劳。在此过程中,下肢肌肉的协同活动呈现非同步性的变化,引起股肌-腓肠肌动力传递效率下降和踝关节拮抗肌共收缩比率增加。

Objective To examine the electromyography(EMG) activities of lower limb muscles and explore the adjustment of muscle coordination during 30-sencond all-out cycling exercise. Methods Ten field cyclists(7 males,3 females,aged 21.5 ± 4.7 yrs) performed a 30-second all-out sprint cycling exercise. The power output,pedalling frequency and surface EMG of the rectus femoris(RF) and vastus(VAS) of the medialis and lateralis muscle,hamstring muscle(HAM) of the biceps femoris and semitendinosus,tibialis anterior(TA),gastrocnemius(GAS) and soleus(SOL) were recorded. The exercises were recorded using a high-speed camera so as to determine the beginning and ending of a pedaling cycle. The EMG amplitude,muscle onset duration time and median frequency(MF) of each muscle as well as the co-activation index(CAI) of three muscle pairs(CAITA/SOL,CAIVAS/GAS and CAIVAS/HAM) were calculated. Results At the end of a pedaling cycle,the pedaling frequency and power output decreased by 21.51% ± 5.40% and 56.17% ± 9.91% compared to the peak values. The EMG amplitude,onset duration time and MF of RF,VAS and GAS decreased significantly with the increase of exercise duration time. CAITA/SOL increased progressively while CAIVAS/GAS showed significant decrease tendency during the pedaling exercise. Conclusions During the 30-second all-out cycling exercise,the average RF,VAS,TA and GAS are of severe muscle fatigue. The activities of lower limb muscles show non-synchronous changes,which reduces the efficiency of the power transmission between VAS and GAS and increases the co-contraction ratio of ankle antagonistic muscles.