The relationships among critical power determined from a 3-min all-out test, respiratory compensation point, gas exchange threshold, and ventilatory threshold

Purpose: Critical power (CP) from the 3-min test was compared to the power outputs associated with thresholds determined from gas exchange parameters that have been used to demarcate the exercise-intensity domains including the respiratory compensation point (RCP), gas exchange threshold (GET), and ventilatory threshold (VT). Method: Twentyeight participants performed an incremental-cycle ergometer test to exhaustion. The VT was determined from the relationship between the ventilatory equivalent for oxygen uptake (V _E/VO₂) versus VO₂ and the GET was determined using the V-slope method (VCO₂ vs. VO₂). The RCP was identified from the VE-versus-VCO₂ relationship. CP was the average power output during the last 30 s of the 3-min all-out test. Linear regression was used to determine the power outputs associated with the RCP, GET, and VT, as well as the VO₂ associated with CP. Mean differences among the associated power outputs, percent VO₂ peak, and percent peak power output for the GET, VT, RCP, and CP were analyzed using separate one-way repeated-measures analyses of variance. Results: There were no significant differences between CP (187 ± 47 W) and the power output associated with RCP (190 ± 49 W) or between the power outputs associated with GET (139 ± 37 W) and VT (145 ± 37 W). The power outputs associated with GET and VT, however, were significantly less than were those at CP and associated with RCP. Conclusions: These findings suggest CP and RCP demarcate the heavy from severe exercise-intensity domain and result from a different mechanism of fatigue than that of GET and VT, possibly hyperkalemia.