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) over dot(E)/(V) over dotO(2)) versus (V) over dotO(2) and the GET was determined using the V-slope method ((V) over dotCO(2) vs. (V) over dotO(2)). The RCP was identified from the (V) over dot(E)-versus-(V) over dotCO(2) 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 (V) over dotO(2) associated with CP. Mean differences among the associated power outputs, percent (V) over dotO(2) 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.