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

Abstract

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 RV(EMGFT) and RV(HRFT). Eleven men performed incremental treadmill exercise to exhaustion on a single occasion. The RV(EMGFT) and RV(HRFT) 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. There was a significant (P < 0.05) difference between the 2 thresholds [RV(EMGFT) = 11.7 ± 0.6 km/h and RV(HRFT) = 8.3 ± 0.8 km/h]. 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.