ELECTRIC MECHANIC DELAYS MEASURED BY PEAK MUSCULAR ACTIVITIES DURING CYCLING WITH DIFFERENT CADENCES

In studies concerning cycling, it was suggested that due to the influence of electromechanical delay (EMD), peak electromyographic activities (PEMG) occur earlier in the crank cycle as cadence increases in order to contribute peak force (PF) at the same position in the crank cycle. This notion was further developed in the proposed Activation Dynamics hypothesis: during cycling with different cadences, shifts in muscle activity were primarily the result of a phase advance to account for the activation dynamics rather than to indicate change in muscle function. PURPOSE To determine EMD by using PEMG during cycling at different frequencies and to determine PF in selected muscles. METHODS Based on the abovementioned hypotheses, the following equations can be established: EMD X cadence = crank angle (PF) – crank angle (PEMG). Applying this equation to two different pedaling frequencies and the EMD of a given muscle can be calculated by (assuming EMG patterns will not be affected by the pedaling cadence): EMD = difference in crank angles of PEMG/difference in cadences. Furthermore, rearranging the first equation: Crank angle (PF) = EMD X cadence + crank angle (PEMG). The crank angle at which a specific muscle might produce peak force can be estimated. These equations were applied to estimate EMDs and crank angles (PF) of selected muscles from the crank angles (PEMG) of 16 subjects while pedaling at 60, 80, and 100 rpm. RESULTS The estimated EMDs are 68.0 and 88.7 ms for tibialis anterior (TA) and soleus (SL), respectively. The estimated crank angles for peak TA forces are 314, 306, and 300 degrees for 60, 80, and 100 rpm, respectively. The estimated crank angles for peak SL forces are 97, 87, and 79 degrees for 60, 80, and 100 rpm, respectively. CONCLSION The proposed method could be used to identify EMD while pedaling with different frequencies.