Stage-to-Stage Changes in Heart Rate-Power Output Coupling During Cycling Stage Races: Associations with Race-Derived Performance and Stage Context.

Abstract

This study examines whether model-derived heart rate-power output (HR-PO) parameters changed across consecutive stages of elite under-23 stage races and whether their longitudinal trajectories were associated with race-derived performance characteristics and stage context. Race files from the 2025 Tour de l'Avenir and Giro Next Gen were analysed, comprising 127 valid stage observations from 23 cyclist-race cases and 19 unique cyclists. For each stage, τ_del, τ_rec, and τ_max were estimated from an HR-PO model, and longitudinal changes were analysed using linear mixed-effects models. The estimated decrease in τ_del across race progression was not statistically significant after FDR correction across the three parameters (-1.33 s, 95% CI -2.45 to -0.20, unadjusted p = 0.021; q = 0.063), whereas τ_rec (0.68 s, 95% CI -6.58 to 7.93, p = 0.855) and τ_max (-0.96 s, 95% CI -2.10 to 0.19, p = 0.101) showed no systematic change. The τ_del trajectory differed between Avenir and Giro (race-by-progression interaction, p = 0.027) and was attenuated after exclusion of the most mountainous stages (-0.85 s, 95% CI -2.56 to 0.85, p = 0.327). In exploratory secondary analyses, higher race-derived PO at 5 s and 5-30 min (p ≤ 0.006, q ≤ 0.043) and better 5 min durability (p < 0.001, q = 0.007) were associated with a more negative τ_rec trajectory; however, cyclist-cluster bootstrap confidence intervals excluded zero only for the 5 s and 5 min PO interactions, and no association was retained for τ_del or τ_max. In stage-context analyses, higher normalized power relative to critical power was associated with higher τ_rec (8.09 s per 10 percentage points; p = 0.001, q = 0.044), whereas greater low-intensity exposure was associated with lower τ_max (-0.82 s per 10 percentage points relative to moderate intensity; p = 0.003, q = 0.045); no stage-context association was retained for τ_del. Overall, the estimated decrease in τ_del did not reach statistical significance after FDR correction and was sensitive to race context and the exclusion of the most mountainous stages, whereas τ_rec showed no systematic longitudinal change but varied in association with race-derived PO, durability, and relative stage intensity. All secondary associations are hypothesis-generating and require independent validation.