Validating the EMG(FT) from a single incremental cycling test

The purposes of this study were to (1) identify the EMG(FT) from a single incremental cycle ergometry test and (2) validate this fatigue threshold by having participants perform constant workload rides at 70, 100 and 130% of the estimated EMG(FT). 11 healthy college-age participants performed incremental cycle ergometry on the initial visit. The EMG amplitude was recorded from the vastus lateralis muscle for each power output and fitted with linear regression which provided the estimated EMG(FT). In subsequent visits, participants exercised at 3 percentages of their EMG(FT) with the EMG amplitude recorded for each condition. The results indicated no significant (p>0.05) increases in EMG amplitude vs. time for the 70% and 100% workloads, respectively. In addition, the participants were able to maintain these exercise intensities for over 40 min. For the 130% workload, however, EMG amplitude vs. time increased significantly (p<0.001) and the participants were able to maintain the exercise condition for less than 12 min. These findings indicate that the EMG(FT) estimated from a single incremental cycle ergometry test is a valid measure of neuromuscular fatigue and may potentially be useful in assessing the efficacy of rehabilitative interventions.