Effect of individual characteristics and aerobic training on the %HRR-% V̇ O 2 R relationship.

This study aimed to assess if, during incremental exercise, considering individual characteristics can make the relationship between the percentages of heart rate (HRR) and oxygen uptake ( V̇ O 2 R) reserve either 1:1 or more accurate. Cycle ergometer data of the maximal incremental exercise tests performed by 450 healthy and sedentary participants (17-66 years) of the HERITAGE Family Study, grouped for sex, ethnicity, age, body fat, resting HR, and V̇ O 2max , were used to calculate the individual linear regressions between %HRR and % V̇ O 2 R. The mean slope and intercept of the individual linear regressions of each subgroup were compared with 1 and 0 (identity line), respectively, using Hotelling tests followed by post-hoc one-sample t -tests. Two multiple linear regressions were also performed, using either the slopes or intercepts of the individual linear regressions as dependent variables and sex, age, resting HR, and V̇ O 2max as independent variables. The mean %HRR-% V̇ O 2 R relationships of all subgroups differed from the identity line. Moreover, individual linear regression intercepts (8.9 ± 16.0) and slopes (0.971 ± 0.190) changed ( p  < 0.001) after 20 weeks of aerobic training (13.1 ± 11.1 and 0.891 ± 0.122). The multiple linear regressions could explain only 3.8% and 1.3% of the variance in the intercepts and slopes, whose variability remained high (standard error of estimate of 15.8 and 0.189). In conclusion, the %HRR-% V̇ O 2 R relationship differs from the identity line regardless of individual characteristics and their difference increased after aerobic training. Moreover, due to the high interindividual variability, using a single equation for the whole population seems not suitable for representing the %HRR-% V̇ O 2 R relationship of a given subject, even when several individual characteristics are considered. HighlightsThe association between %HRR and % V̇ O 2 R is not 1:1 even when individuals are grouped by age, sex, ethnicity, body composition, HR rest , and V̇ O 2max .Using several subject characteristics to identify the individual's %HRR-% V̇ O 2 R relationship does not meaningfully increase its prediction accuracy or reduce the interindividual variability of %HRR-% V̇ O 2 R relationshipsUsing a single equation for the whole population is not suitable for representing the relationship of a given subject; hence, individual relationships should be preferred when prescribing the intensity of aerobic exercise.The individual %HRR-% V̇ O 2 R relationship should be periodically assessed due to the potential training induced changes in the relationship.