Accuracy of Commonly Used Age-Predicted Maximal Heart Rate Equations

Abstract

Age-predicted maximal heart rate (APMHR) is an essential measure for healthcare professionals in determining cardiovascular response to exercise testing, exertion, and prescription. Although multiple APMHR prediction equations have been validated for specific populations, the accuracy of each within a general population requires testing. We aimed to determine which APMHR equation (Fox, Gellish, Gulati, Tanaka, Arena, Astrand, Nes, Fairbarn) most accurately predicts max heart rate (HR_max) in a general population. HR_max from 99 graded treadmill exercise tests (GXT) were measured. GXTs ended upon volitional fatigue and were only included for analysis if RER > 1.10. Individual paired t-test were performed to determine if significant differences existed between measured and predicted HR_max, along with root mean square errors for each equation. Bland-Altman plots were constructed to determine agreement between equations and measured HR_max. Significant differences between measured and predicted HRmax were found for the Gulati, Astrand, Nes, and Fairbarn (male) equations (p < 0.05). Bland-Altman plots revealed wide limits of agreement for all nine APMHR equations, suggesting poor agreement between measured and predicted HR_max. Proportional bias indicates that prediction equations under and overestimated HR_max in individuals with lower and higher measured HR_max, respectively, with the exception of the Fox equation. All equations used in this study show poor agreement between measured HR_max and APMHR. The Fox equation may represent the best option for a general population as it is less likely to under or overestimate based on individual HR_max. Individuals should use data from GXTs to determine HR_max when applicable to ensure accuracy.

Keywords: Exercise testing; aerobic exercise; exercise intensity prescription.

Figure 1

Bland-Altman plots showing agreement between measured and predicted HRmax. The vertical axes represent the difference in heart rate (bpm) between HR_max during GXT and HR_max as predicted by each equation. The horizontal axes represent the mathematical average for each participants HR_max measurements. The middle dashed line represents bias, while the upper and lower dashed lines represent the upper (+2SD) and lower (−2SD) limits of agreement. The dotted lines surrounding each dashed line represent the confidence intervals of the bias (middle), upper, and lower levels of agreement.