Comparison of electromyographic responses for the superficial quadriceps muscles: cycle versus knee-extensor...

The purpose of this study was to compare the electromyographic (EMG) amplitude and mean power frequency (MPF) versus power output relationships for the three superficial quadriceps muscles during incremental cycle (CE) and knee-extensor (KE) ergometry in the same subjects. Eight men performed incremental CE and KE tests to exhaustion. Surface EMG signals were recorded simultaneously from the vastus lateralis (VL), rectus femoris (RF), and vastus medialis (VM). Polynomial regression analyses on a subject-by-subject basis indicated that the relationship between EMG amplitude versus power output was best-fit with either a linear, quadratic, or cubic model for CE, whereas the relationship was best-fit with a linear model for all subjects for the KE test. No consistent relationship was found for EMG MPF within subjects and between muscle groups for CE or KE. Compared with CE, however, the EMG amplitude during KE exercise was, on average, approximately 87% and 30% higher for the RF and VM muscles, respectively. These results suggest that KE exercise may be a better mode of examining EMG amplitude in the quadriceps muscle during incremental exercise than traditional CE.