AUTHOR=Ausland Ådne , Kelemen Bence , Seiler Stephen 
  
TITLE=An exploratory study of maximal heart rate determination in endurance athletes: laboratory testing vs. field based
  
JOURNAL=Frontiers in Sports and Active Living
  
VOLUME=Volume 8 - 2026
  
YEAR=2026
  
URL=https://www.frontiersin.org/journals/sports-and-active-living/articles/10.3389/fspor.2026.1806303
  
DOI=10.3389/fspor.2026.1806303
  
ISSN=2624-9367
  
ABSTRACT=BackgroundAccurate 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.MethodsA 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.ResultsAge 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.ConclusionsThis 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.