AN EXAMINATION OF THE ELECTROMYOGRAPHIC FATIGUE THRESHOLD TEST

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.