Revisiting age-predicted maximal heart rate: Can it be used as a valid measure of effort?

Despite high error ranges, age-predicted maximal heart rate (APMHR) is frequently used to gauge the achievement of adequate effort during an exercise test. The current analysis revisits this issue using the Fitness Registry and the Importance of Exercise: National Database (FRIEND Registry).

A total of 4,796 (63% male) apparently healthy subjects underwent a maximal cardiopulmonary exercise test on a treadmill. The mean age, maximal heart rate (HR), and maximal aerobic capacity of the cohort were 43 ± 12 years, 178 ± 15 beats per minute, and 36.1 ± 10.6 mlO2 · kg(-1) · min(-1), respectively. All subjects reached or surpassed a peak respiratory exchange ratio of 1.10. A linear regression equation using age to predict maximal HR was validated in 3,796 subjects and cross-validated in the remaining 1,000 (randomly assigned).

The APMHR equation in the validation cohort was as follows: 209.3 - 0.72(age). The r value and standard error of estimate for this regression was 0.61 (P < .001) and 11.35 beats/min, respectively. A 1-sample t test revealed that the mean difference between actual maximal HR and APMHR was not significantly different from 0 (mean difference = 0.32, P = .43). However, Bland-Altman revealed high limits of agreement (upper 25.31 and lower -24.67) and a significant proportional bias.

The APMHR equation derived from this analysis included a large cohort of apparently healthy individuals with maximal exercise effort validated by the criterion standard (ie, peak respiratory exchange ratio). Using APMHR in this capacity should be discouraged, and new approaches to gauging an individual's exercise effort should be explored.