Prilutsky B I, Gregor R J, Ryan M M
Department of Health and Performance Sciences, Center for Human Movement Studies, The Georgia Institute of Technology, Atlanta 30332-0110, USA.
Exp Brain Res. 1998 Jun;120(4):479-86. doi: 10.1007/s002210050421.
It has been hypothesized previously that because a strong correlation was found between the difference in electromyographic activity (EMG) of rectus femoris (RF) and hamstrings (HA; EMG(RF)-EMG(HA)) and the difference in the resultant moments at the knee and hip (Mk-Mh) during exertion of external forces on the ground by the leg, input from skin receptors of the foot may play an important role in the control of the distribution of the resultant moments between the knee and hip by modulating activation of the two-joint RF and HA. In the present study, we examined the coordination of RF and HA during the swing phase of walking and running at different speeds, where activity of foot mechanoreceptors is not modulated by an external force. Four subjects walked at speeds of 1.8 m/s and 2.7 m/s and ran at speeds of 2.7 m/s and 3.6 m/s on a motor-driven treadmill. Surface EMG of RF, semimembranosus (SM), and long head of biceps femoris (BF) and coordinates of the four leg joints were recorded. An inverse dynamics analysis was used to calculate the resultant moments at the ankle, knee, and hip during the swing phase. EMG signals were rectified and low-pass filtered to obtain linear envelopes and then shifted in time to account for electromechanical delay between EMG and joint moments. During walking and running at all studied speeds, mean EMG envelope values of RF were statistically (P<0.05) higher in the first half of the swing (or at hip flexion/knee extension combinations of joint moments) than in the second half (or at hip extension/knee flexion combinations of joint moments). Mean EMG values of BF and SM were higher (P<0.05) in the second half of the swing than in the first half. EMG and joint moment peaks were substantially higher (P<0.05) in the swing phase of walking at 2.7 m/s than during the swing phase of running at the same speed. Correlation coefficients calculated between the differences (EMG(RF)-EMG(HA)) and (Mk-Mh), taken every 1% of the swing phase, were higher than 0.90 for all speeds of walking and running. Since the close relationship between EMG and joint moments was obtained in the absence of an external force applied to the foot, it was suggested that the observed coordination of RF and HA can be regulated without a stance-specific modulation of cutaneous afferent input from the foot. The functional role of the observed coordination of RF and HA was suggested to reduce muscle fatigue.
此前有假设认为，由于在腿部对地面施加外力时，股直肌（RF）和腘绳肌（HA；即EMG(RF)-EMG(HA)）的肌电图活动差异与膝关节和髋关节的合成力矩差异（Mk-Mh）之间存在强烈相关性，足部皮肤感受器的输入可能通过调节双关节RF和HA的激活，在控制膝关节和髋关节之间合成力矩的分布中发挥重要作用。在本研究中，我们研究了在不同速度的步行和跑步摆动阶段RF和HA的协调性，此时足部机械感受器的活动不受外力调节。四名受试者在电动跑步机上以1.8米/秒和2.7米/秒的速度行走，以及以2.7米/秒和3.6米/秒的速度跑步。记录了RF、半膜肌（SM）和股二头肌长头（BF）的表面肌电图以及四个腿部关节的坐标。采用逆动力学分析来计算摆动阶段踝关节、膝关节和髋关节的合成力矩。对肌电图信号进行整流和低通滤波以获得线性包络，然后在时间上进行移位，以考虑肌电图和关节力矩之间的机电延迟。在所有研究速度的步行和跑步过程中，RF的平均肌电图包络值在摆动的前半段（或在关节力矩的髋关节屈曲/膝关节伸展组合时）在统计学上（P<0.05）高于后半段（或在关节力矩的髋关节伸展/膝关节屈曲组合时）。BF和SM的平均肌电图值在摆动的后半段高于前半段（P<0.05）。在2.7米/秒步行的摆动阶段，肌电图和关节力矩峰值显著高于相同速度跑步的摆动阶段（P<0.05）。在摆动阶段的每1%计算的差异（EMG(RF)-EMG(HA)）和（Mk-Mh）之间的相关系数，在所有步行和跑步速度下均高于0.90。由于在未对足部施加外力的情况下获得了肌电图和关节力矩之间的密切关系，因此表明观察到的RF和HA的协调性可以在不依赖于足部皮肤传入输入的特定站立调节的情况下进行调节。观察到的RF和HA协调性的功能作用被认为是减少肌肉疲劳。
