Neptune R R, Kautz S A, Hull M L
Department of Mechanical Engineering, University of California, Davis 95616, USA.
J Biomech. 1997 Oct;30(10):1051-8. doi: 10.1016/s0021-9290(97)00071-7.
To further understand lower extremity neuromuscular coordination in cycling, the objectives of this study were to examine the effect of pedaling rate on coordination strategies and interpret any apparent changes. These objectives were achieved by collecting electromyography (EMG) data of eight lower extremity muscles and crank angle data from ten subjects at 250 W across pedaling rates ranging from 45 to 120 RPM. To examine the effect of pedaling rate on coordination, EMG burst onset and offset and integrated EMG (iEMG) were computed. In addition, a phase-controlled functional group (PCFG) analysis was performed to interpret observed changes in the EMG patterns in the context of muscle function. Results showed that the EMG onset and offset systematically advanced as pedaling rate increased except for the soleus which shifted later in the crank cycle. The iEMG results revealed that muscles responded differently to increased pedaling rate. The gastrocnemius, hamstring muscles and vastus medialis systematically increased muscle activity as pedaling rate increased. The gluteus maximus and soleus had significant quadratic trends with minimum values at 90 RPM, while the tibialis anterior and rectus femoris showed no significant association with pedaling rate. The PCFG analysis showed that the primary function of each lower extremity muscle remained the same at all pedaling rates. The PCFG analysis, which accounts for muscle activation dynamics, revealed that the earlier onset of muscle excitation produced muscle activity in the same region of the crank cycle. Also, while most of the muscles were excited for a single functional phase, the soleus and rectus femoris were excited during two functional phases. The soleus was classified as an extensor-bottom transition muscle, while the rectus femoris was classified as a top transition-extensor muscle. Further, the relative emphasis of each function appeared to shift as pedaling rate was increased, although each muscle remained bifunctional.
为了进一步了解骑行过程中下肢的神经肌肉协调性，本研究的目的是检验蹬踏频率对协调策略的影响，并解释任何明显的变化。通过收集10名受试者在250瓦功率下，蹬踏频率范围为45至120转/分钟时，八个下肢肌肉的肌电图（EMG）数据和曲柄角度数据，实现了这些目标。为了检验蹬踏频率对协调性的影响，计算了EMG爆发的起始和结束时间以及积分肌电图（iEMG）。此外，进行了相位控制功能组（PCFG）分析，以在肌肉功能的背景下解释观察到的EMG模式变化。结果表明，除比目鱼肌在曲柄周期中延迟外，随着蹬踏频率的增加，EMG的起始和结束时间有系统性提前。iEMG结果显示，肌肉对蹬踏频率增加的反应不同。随着蹬踏频率增加，腓肠肌、腘绳肌和股内侧肌的肌肉活动系统性增加。臀大肌和比目鱼肌有显著的二次趋势，在90转/分钟时达到最小值，而胫前肌和股直肌与蹬踏频率无显著关联。PCFG分析表明，在所有蹬踏频率下，每个下肢肌肉的主要功能保持不变。考虑到肌肉激活动态的PCFG分析表明，肌肉兴奋的提前起始在曲柄周期的相同区域产生了肌肉活动。此外，虽然大多数肌肉在单个功能阶段被激发，但比目鱼肌和股直肌在两个功能阶段被激发。比目鱼肌被归类为伸展-底部过渡肌肉，而股直肌被归类为顶部过渡-伸展肌肉。此外，尽管每个肌肉仍然具有双功能，但随着蹬踏频率的增加，每个功能的相对重点似乎发生了变化。
