The effect of pedaling rate on coordination in cycling.

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.