PHASIC MUSCLE ACTIVITY OF THE LOWER EXTREMITY AT DIFFERENT POWERS AND PEDALLING CADENCES IN CYCLE ERGOMETRY

Abstract

Changes in muscle activity occur with changes in cycling cadence and power output. An understanding of these changes can aid in strength training and performance evaluation. Although the integrated EMG has been frequently studied, phasic muscle activity is evaluated less often. Phasic activity was measured relative to the crank position from 0º at top dead center (TDC) through a fill revolution. Four muscles on three experienced recreational cyclists were monitored at cadences of 60rpm, 80rpq and l00rpm and at power levels of 150W, 300W, and 450W. Surface electrodes and videography were utilized to determine the start and stop position of muscle activity relative to each crank revolution. A fill-rectification of the raw EMG signal was then used to determine activity above the threshold. Rectus femoris activity started earlier in the crank cycle with each increase in cadence. However, it stopped later for only the first increment in cadence and remained constant for the second. These changes increased the duration of muscle activity at the higher cadences. Power output had no effect on the duration of rectus femoris activity, however the activity did shift relative to the crank cycle. The vastus lateralis activity showed similar changes in duration. Relative to power output, the duration of vastus lateralis activity was higher at the highest power output. The gluteus maximus and biceps femoris were also considered, but were not analyzed. The EMG results of the gluteus maximus had a small magnitude that was obscured by noise. The start and stop points of the biceps femoris activity were obscured when the asymmetrical raw EMG pattern was My rectified. Further study of these muscles as well as larger sample size would enhance the knowledge for improved cycle training.