ABSTRACT
INTRODUCTION: The purposes of this investigation were to determine the: (1) reproducibility of the patterns of responses for electromyographic (EMG) amplitude and mean power frequency (MPF); and (2) intraclass correlation coefficient (ICC) of the EMG amplitude and MPF during three incremental cycle ergometer tests separated by 48 hours. METHODS: Ten men performed incremental cycle ergometry tests to exhaustion on three separate occasions. Surface EMG signals were recorded simultaneously from the three superficial quadriceps muscles at each trial. RESULTS: Polynomial regression indicated that, for >95% of the cases, the best-fit model was the same at each trial for EMG amplitude but not for EMG MPF. The ICC values were high for EMG amplitude but low for EMG MPF. CONCLUSIONS: These results indicate that EMG amplitude is a reliable measure of motor unit activation strategy during incremental cycle ergometry, whereas the EMG MPF was unreliable.
