An examination of the electromyographic fatigue threshold test

Summary

The purpose of this investigation was to examine times to exhaustion at various percentages of the electromyographic fatigue threshold (EMG_FT). Eight adult males [mean (SD), 21 (1) years] volunteered for the investigation. EMG_FT was derived by determining the rate of rise in the electrical activity of the vastus lateralis [using integrated electromyography (iEMG)] over time (iEMG slope) for four fatiguing power outputs during cycle ergometry. The four power outputs were then plotted as a function of the four iEMG slope coefficients. The y-intercept of the power output versus iEMG slope coefficient graph was defined as the EMG_FT. The intraclass correlation for repeated EMG_FT tests was R=0.65 (SEE=7 W) and there was no significant (P>0.05) difference between the mean (SD) values for test [260 (11) W] versus retest [262 (32) W]. Actual times to exhaustion were determined for work bouts at power outputs equal to 85, 100, 115, 130, and 145% of EMG_FT. The mean (SD) times to exhaustion for these work bouts were 495 (231), 225 (72), 135 (35), 94 (17), and 72 (14) s, respectively. A power curve was derived using the mean power outputs and mean times to exhaustion from the five rides at various percentages of EMG_FT. The power curve provided estimates of the power outputs which could be maintained for 30 and 60 min. There were significant (P<0.05) differences between the mean EMG_FT (260 W) and the power outputs which could be maintained for 30 (151 W) and 60 (125 W) min. EMG_FT overpredicted the estimated power outputs that could be maintained for 30 and 60 min by 42% and 52%, respectively.