Electromyographic responses at the neuromuscular fatigue threshold.

The purposes of this investigation were to: (a) examine the electromyographic (EMG) responses from the vastus lateralis during a continuous ride to exhaustion at the neuromuscular fatigue threshold (EMGFT) and (b) determine what percentage of the power output at VO2max the EMGFT represents. Fifteen adult males (mean +/- SD = 22 +/- 2 years) volunteered to perform an EMGFT test and a continuous ride to exhaustion at the EMGFT on separate days. A subsample of ten subjects completed an incremental cycle ergometer test for the determination of VO2max. The mean (+/- SD) EMGFT for the total sample (n = 15) was 286 +/- 40W and the mean time to exhaustion at the EMGFT was 250 +/- 85 sec. For each subject, the slope of the iEMG versus time relationship during the continuous ride to exhaustion at the EMGFT was significantly (p < 0.05) greater than zero slope. For the subsample (n = 10), the mean EMGFT (296 +/- 45W) was not significantly (p > 0.05) different from the power output at VO2max (282 +/- 47W). These findings did not support the contention that the EMGFT can be sustained without electromyographic evidence of neuromuscular fatigue and indicated that the EMGFT was comparable to the power output at VO2max.