Estimated times to exhaustion and power outputs at the gas exchange threshold, physical working capacity at the rating of perceived exertion threshold, and respiratory compensation point

The purposes of this study were to compare the power outputs and estimated times to exhaustion (Tlim) at the gas exchange threshold (GET), physical working capacity at the rating of perceived exertion threshold (PWCRPE), and respiratory compensation point (RCP). Three male and 5 female subjects (mean ± SD: age, 22.4 ± 2.8 years) performed an incremental test to exhaustion on an electronically braked cycle ergometer to determine peak oxygen consumption rate, GET, and RCP. The PWCRPE was determined from ratings of perceived exertion data recorded during 3 continuous workbouts to exhaustion. The estimated Tlim values for each subject at GET, PWCRPE, and RCP were determined from power curve analyses (Tlim = ax ^b). The results indicated that the PWCRPE (176 ± 55 W) was not significantly different from RCP (181 ± 54 W); however, GET (155 ± 42 W) was significantly less than PWCRPE and RCP. The estimated Tlim for the GET (26.1 ± 9.8 min) was significantly greater than PWCRPE (14.6 ± 5.6 min) and RCP (11.2 ± 3.1 min). The PWCRPE occurred at a mean power output that was 13.5% greater than the GET and, therefore, it is likely that the perception of effort is not driven by the same mechanism that underlies the GET (i.e., lactate buffering). Furthermore, the PWCRPE and RCP were not significantly different and, therefore, these thresholds may be associated with the same mechanisms of fatigue, such as increased levels of interstitial and (or) arterial [K ⁺].