Estimating electromyographic and heart rate fatigue thresholds from a single treadmill test

Introduction: The purposes of this study were to (1) develop a fatigue threshold based on electromyography (EMG) and heart rate (HR) responses for treadmill running from a single incremental test; and (2) propose a new fatigue threshold called the RVEMGFT and RVHRFT. Methods: Eleven men performed incremental treadmill exercise to exhaustion on a single occasion. The RVEMGFT and RVHRFT were defined as the average of the highest velocity that resulted in a nonsignificant slope coefficient for the EMG amplitude versus time relationship and the lowest velocity that resulted in a significant positive slope coefficient. Results: There was a significant (P < 0.05) difference between the 2 thresholds [RVEMGFT = 11.7 ± 0.6 km/h and RVHRFT = 8.3 ± 0.8 km/h]. Conclusions: The fatigue threshold for EMG amplitude and heart rate can be determined from a single incremental treadmill test, but there are differences between cardiac and neuromuscular factors of fatigue. Muscle Nerve 46: 577–581, 2012