An exploratory study of maximal heart rate determination in endurance athletes: laboratory testing vs. field based

Accurate assessment of cardiovascular parameters, including maximal heart rate (HRmax), resting heart rate (RHR), and heart rate reserve (HRR), is important for guiding training prescriptions in endurance athletes. Conventional age-based HRmax prediction formulas, particularly the widely used "220-age" equation, remain common despite substantial individual variation and documented underestimation in trained populations. Self-reported field data-defined as the highest heart rate recorded during maximal training or racing efforts-provide an ecologically valid alternative for examining HRmax in real-world settings.

A cross-sectional study was conducted with 4,375 endurance athletes across multiple disciplines. Self-reported HRmax, RHR, weekly training load, and training history were collected via standardized web-based surveys administered globally from November 2022 to January 2023. Associations were evaluated using Pearson correlations, and the accuracy of age-based HRmax formulas was assessed via Bland-Altman analyses.

Age was strongly inversely correlated with HRmax (r = -0.60, p < 0.001) and HRR (r = -0.66, p < 0.001), but only weakly associated with RHR (r = 0.06, p < 0.001). Age-based formulas underestimated self-reported HRmax by 5-6 bpm (mean bias = -5.8 bpm for Fox; -4.8 bpm for Tanaka), with wide limits of agreement (Tanaka: -18.5 to +9.1 bpm; Fox: -20.2 to +8.6 bpm), indicating substantial individual variability. RHR was moderately inversely correlated with weekly training hours (r = -0.23, p < 0.001). No significant sex differences were observed. HRR exhibited high inter-individual variability.

This exploratory analysis of self-reported field data demonstrates that age-based HRmax formulas show systematic underestimation and wide individual error in endurance athletes. These findings support the use of individualized, context-specific HRmax assessment, while highlighting the limitations of relying solely on age-based predictions.