How is rating of perceived capacity related to VO2max and what is VO2max at onset of training?

Objective To evaluate how rating of perceived capacity (RPC) is related to maximal oxygen uptake (VO2max) and examine VO2max at onset of training in healthy adults. Methods In total, 125 newly registered fitness centre members, equally men and women, answered the RPC scale and performed a treadmill test for measurement of VO2max. Eligible criteria were <4 weeks of fitness centre membership, physically inactive, ≥18 years and not pregnant. The RPC is a one-page scale (1-20) based on metabolic equivalent tasks, where the individual chooses the most strenuous activity that can be sustained for at least 30 min. Results The Bland-Altman plot demonstrated a tendency of overestimation, meaning that the participants ranked their own aerobic capacity 17.5% higher than objectively measured values of VO2max. The mean difference between the two methods were +4.92±1.96 and +6.35±1.96 mL/min/kg VO2 in men and women, respectively. The Pearson correlation coefficient was moderate, with r=0.426 (p<0.01). A linear regression analysis showed that both age and VO2max were significant predictors of RPC (p<0.01). Measured VO2max at onset of fitness centre membership was in men aged 38.7±11.7 and women aged 34.7±9.9, 40.5±7.2 and 35.0±6.0 mL/min/kg, respectively. Estimated VO2max from the RPC scale was 45.7±9.8 and 41.4±10.1 mL/min/kg in men and women, respectively. Conclusions The RPC seems less accurate at the individual level and may overestimate VO2max. Still, it may be considered useful in large-scale studies.