Relationships Among Maximal Oxygen Consumption, Ventilatory Threshold, and Elactromyographic Fatigue Threshold as Performance Assessments in College Women

PURPOSE: The purpose of this study was to examine the relationships among the power outputs (W) and VO2 values (L/min) at VO2PEAK, ventilatory threshold (VT), and electromyographic fatigue threshold (EMGFT). METHODS: Thirty-seven active women (mean ± SD: 22.03 ± 3.97 years; 166.75 ± 6.73 cm; 66.51 ± 11.14 kg) volunteered to perform two cycling tests on an electronically-braked cycle ergometer. An initial incremental exercise test was performed until exhaustion (increase of 25 W every 2 min) to determine VO2PEAK and VT. Each participant also performed a discontinuous incremental cycle ergometer test to determine their EMGFT. Four, two-minute work bouts (ranging from 75-250 W) were completed starting at each participant's power output at VT and increasing 25 W each consecutive work bout. A bipolar surface electrode arrangement, placed on the vastus lateralis of the right thigh was used to record EMG amplitude, averaged over 10 s intervals during each cycling bout. The four power outputs were plotted as a function of four EMG slope coefficients, with the y-intercept defined as the EMGFT. In addition, a regression analysis was performed to predict the VO2 value at EMGFT. Two one-way repeated measures ANOVAs were used to examine differences among power output and VO2 (L/min) measures. RESULTS: For power outputs, significant differences were observed between VO2PEAK and VT (p < 0.001; r = 0.613), VT and EMGFT (p = 0.016; r = 0.682), and VO2PEAK and EMGFT (p < 0.001; r = 0.559). For VO2, significant differences were observed between VO2PEAK and VT (p < 0.001) and VO2PEAK and EMGFT (p < 0.001). The correlations among VO2PEAK and VT, VT and EMGFT, and VO2PEAK and EMGFT were r = 0.777, 0.773, and 0.737, respectively, for VO2 values. CONCLUSION: The means at which power output and VO2 occurred for VO2PEAK, VT, and EMGFT were significantly different from each other except for the VO2 values at EMGFT and VT. This similarity, in addition to the moderate correlation of 0.773, suggested that predicted VO2 at EMGFT and VT may reflect similar physiological factors involved with the onset of fatigue during incremental exercise. Therefore, suggesting that there is a close association between the onset of peripheral fatigue measured by surface EMG and the ventilatory breakpoint that is calculated from collected gases measured with open-circuit spirometry.