Within-Athlete Associations Between WHOOP Activity Strain, Coach-Prescribed Training Objectives, and Session-RPE in an Elite Junior Swimmer: A Longitudinal Single-Case Study.
Petrov Á, Barthalos I, Arany D, Nagyváradi K, Petrov I, Alföldi Z et al. · Journal of functional morphology and kinesiology · 2026
Background and objectives: Wearable technologies increasingly monitor internal training load in high-performance sport, but their alignment with coach-prescribed physiological
Objectives: remains unclear. This study examined within-athlete associations between WHOOP Activity Strain, coach-prescribed
objectives, athlete-perceived load, and completed swimming exposure in one elite junior swimmer.
Methods: An exploratory longitudinal single-case secondary analysis was conducted using routinely collected training and athlete-monitoring data from 4 January to 3 July 2026. WHOOP Activity Strain and Session-RPE were synchronized by session, and generalized estimating equations assessed differences across prescribed
objectives and variable associations.
Results: Of 161 sessions with exact-plan cards, 134 were classified and 128 had strict WHOOP matches. Conventional robust-covariance GEE suggested an
Objective: -related difference (exchangeable p = 0.013; AR(1) p = 0.014), but this was not statistically detectable with the bias-reduced covariance estimator ( p = 0.080 and p = 0.075, respectively) and was not reproduced using the legacy classification. WHOOP Activity Strain was consistently associated with Session-RPE Load, Session-RPE, and actual swimming distance.
Conclusions: Within this athlete, WHOOP Activity Strain was associated with perceived load and completed swimming distance.
Objective-related differences were post hoc and sensitive to the classification source and covariance estimator; they should therefore be considered exploratory and hypothesis-generating.