Heart rate reserve is equivalent to %VO(2)Reserve, not to %VO2max

Percentage of heart rate reserve (%HRR) is widely considered to be equivalent to % of maximal oxygen consumption (%V over dotO(2max)) for exercise prescription purposes. However, this relationship has not been established in the literature, and a theoretically stronger case can be made for an equivalency between %HRR and %VO(2)Reserve (%V over dotO(2R)), (i.e., the difference between resting and maximal V over dotO(2). The current study hypothesized that %HRR is equivalent to %V over dotO(2), not %V over dotO(2), and that the discrepancy between %HRR and %V over dotO(2max) would be inversely proportional to fitness level. Sixty-three adults performed incremental maximal exercise tests on an electrically braked cycle ergometer. HR and V over dotO(2) at rest, at the end of each stage of exercise, and at maximum were used to perform linear regressions on %HRR versus %V over dotO(2max), and %HRR versus %V over dotO(2R) for each subject. For %HRR versus %V over dotO(2max), the mean intercept and slope were -11.6 +/- 1.0 and 1.12 +/- 0.01, respectively, which were significantly different (P < 0.001) from 0 and 1, respectively For %HRR versus %V over dotO(2R), the mean intercept and slope were -0.1 +/- 0.6 and 1.00 +/- 0.01, respectively, which were not distinguishable from the line of identity. There was a significant (P < 0.01) inverse relationship between fitness level (V over dotO(2max)) and the discrepancy between %HRR and %V over dotO(2max). In conclusion, %HRR should not be considered equivalent to %V over dotO(2max). Rather, %HRR is equivalent to %V over dotO(2R), and this relationship should be used in exercise prescription.