Effect of Gas Exchange Measurements on Critical Power and Determination of Peak Oxygen Uptake during 3 min Critical Power Tests

Abstract

No data have been reported regarding the effect of performing gas exchange measurements during 3 min “all-out” tests of cycling Critical Power (CP) on the CP value itself. Conflicting data exists regarding the validity of determining peak oxygen uptake (VO2peak) during 3 min CP tests. PURPOSE: To determine if differences exist between CP measurements performed with metabolic gas exchange data (WMD) and without (Control) during 3 min leg cycling tests. A second aim of this study was to determine if VO2peak can be determined using data from the 3 min CP test. METHODS: Nineteen physically active (VO2peak = 34.7 ± 7.7 ml/kg/min) subjects completed a ramp test to determine VO2peak and two 3 min CP tests (WMD and control). VO2peak was determined from an average of the last 30 sec of the ramp test and compared to VO2 measured during the final 30 sec of the WMD CP test. Critical power (watts) was the mean power attained during the last 30 sec of the CP tests. The curvature constant (W’) was computed as the power-time integral above CP. RESULTS: No differences (p = 0.11) were observed for CP in the WMD trial compared to the control condition (172 ± 46 W, 169 ± 49 W, respectively). Similarly, no differences occurred for W’ (11.3 ± 5.4 kJ WMD, 11.7 ± 4.4 kJ control, p = 0.61) and peak watts (673 ± 326 W WMD, 636 ± 335 W control, p = 0.84). In regard to VO2peak measured during the CP test (2517 ± 576 ml/min) and that of the ramp test (2564 ± 550 ml/min), there were no differences (p = 0.23). CONCLUSIONS: These data indicate that CP, peak W, and W’ values do not differ between a 3 min all-out test performed with or without gas exchange measurements. Thus, one can be confident that performing metabolic gas measures during the 3 min CP test does not bias the CP and W’ data. As no significant differences were found for VO2peak between the ramp and CP test, the data supports the contention that it is possible to obtain VO2peak in a 3 min all-out CP test.