Oxygen Uptake, Heart Rate, and Ratings of Perceived Exertion at the PWCVO2

Abstract

PURPOSE: Theoretically, the PWCVO2 (physical working capacity at the oxygen consumption threshold) is a test that provides an estimate of the maximal power output that can be maintained for an extended period of time without a fatigue-induced increase in the rate of oxygen consumption. The purpose of the present study was to examine the oxygen uptake (VO2), heart rate (HR) and ratings of perceived exertion (RPE (OMNI 0-10)) responses during continuous 1-hr cycle ergometer rides at the PWCVO2. METHODS: Eight male and female volunteers (mean age ± SD = 23 ± 3.2 years) performed an incremental (30W increase every 2 minutes) test to exhaustion on an electronically braked cycle ergometer for the determination of VO2peak and the ventilatory threshold (VT). The subjects also performed four randomly ordered workbouts to exhaustion at different power outputs (ranging from 84 to 245W) to determine the PWCVO2. Each subject then performed a continuous 1-hr cycle ergometer ride at the PWCVO2 during which VO2, HR, and RPE data were collected every 2 min. RESULTS: The PWCVO2 ( mean ± SD = 114 ± 39W) and VT (133 ± 44W) were not significantly different (p>0.05) and occurred at 56 and 63% VO2peak, respectively. Linear regression showed that the slope coefficients for the VO2, HR, and RPE vs. time relationships for the continuous 1-hr workbouts were significantly greater (p<0.05) than zero. Furthermore, a t-test about a single mean indicated that the mean slope coefficient for the HR vs. time relationship was significantly greater than 0.1bpm·min-1 (the rate of increase in HR that can be maintained for an 8-hr day). CONCLUSIONS: The results of this study indicated that PWCVO2 could be maintained for an extended period of time. However, the maximal power output associated with steady-state VO2, HR, and RPE responses was overestimated. The mean increase in VO2 during the continuous 1-hr ride was 270 ml which suggested that the PWCVO2 may demarcate the moderate from heavy exercise domains. The mean HR slope coefficient of 0.3bpm·min-1 indicated that the power output at the PWCVO2 could likely be maintained for greater than 2 hours.