THE EFFECT OF PEDALING RATE ON COORDINATION IN CYCLING

To further understand lower extremity neuromuscular coordination in cy cling, the objectives of this study were to examine the effect of peda ling rate on coordination strategies and interpret any apparent change s. These objectives were achieved by collecting electromyography (EMG) data of eight lower extremity muscles and crank angle data from ten s ubjects at 250 W across pedaling rates ranging from 45 to 120 RPM. To examine the effect of pedaling rate on coordination, EMG burst onset a nd offset and integrated EMG (iEMG) were computed. In addition, a phas e-controlled functional group (PCFG) analysis was performed to interpr et observed changes in the EMG patterns in the context of muscle funct ion. Results showed that the EMG onset and offset systematically advan ced as pedaling rate increased except for the soleus which shifted lat er in the crank cycle. The iEMG results revealed that muscles responde d 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 signifi cant quadratic trends with minimum values at 90 RPM, while the tibiali s anterior and rectus femoris showed no significant association with p edaling rate. The PCFG analysis showed that the primary function of ea ch lower extremity muscle remained the same at all pedaling rates. The PCFG analysis, which accounts for muscle activation dynamics, reveale d that the earlier onset of muscle excitation produced muscle activity in the same region of the crank cycle. Also, while most of the muscle s were excited for a single functional phase, the soleus and rectus fe moris were excited during two functional phases. The soleus was classi fied as an extensor-bottom transition muscle, while the rectus femoris was classified as a top transition-extensor muscle. Further, the rela tive emphasis of each Function appeared to shift as pedaling rate was increased, although each muscle remained bifunctional. (C) 1997 Elsevi er Science Ltd.