THE RELATIONSHIP BETWEEN ANAEROBIC THRESHOLD AND ELECTROMYOGRAPHIC FATIGUE THRESHOLD IN COLLEGE-WOMEN

The purpose of this study was to investigate the relationship between anaerobic threshold (Th(an)) and muscle fatigue threshold (EMG(FT)) as estimated from electromyographic (EMG) data taken from the quadriceps muscles (vastus lateralis) during exercise on a cycle ergometer. The subjects in this study were 20 female college students, including highly trained endurance athletes and untrained sedentary individuals, whose fitness levels derived from their maximal oxygen consumption ranged from 24.9 to 62.2 ml.kg-1.min-1. The rate of increase in integrated EMG (iEMG) activity as a function of time (iEMG slope) was calculated at each of four constant power outputs (350, 300, 250, 200 W), sufficiently high to bring about muscle fatigue. The iEMG slopes so obtained were plotted against the exercise intensities imposed, resulting in linear plots which were extrapolated to zero slope to give an intercept on the power axis which was in turn interpreted as the highest exercise intensity sustainable without electromyographic evidence of neuromuscular fatigue (EMG(FT)). The Th(an) was estimated from gas exchange parameters during an incremental exercise test on the same cycle ergometer. The mean results indicated that oxygen uptake (VO2) at Th(an) was 1.39 1.min-1, SD 0.44 and VO2 at EMG(FT) was 1.33 1.min-1, SD 0.57. There was no significant difference between these mean values (P > 0.05) and there was a highly significant correlation between VO2 at Th(an) and VO2 at EMG(FT) (r = 0.823, P < 0.01). These data supported the concept of Th(an) on the basis that Th(an) was associated with the highest exercise intensity that could be sustained without evidence of neuromuscular fatigue and thus suggested that EMG(FT) may provide an attractive alternative to the measurement of Th(an).