Longitudinal transcriptomic monitoring of erythropoietic adaptations in endurance athletes: a prospective study protocol.

Understanding systemic molecular adaptations to endurance training and environmental hypoxia is important for advancing physiological monitoring in athletes. Transcriptomic profiling of peripheral blood mononuclear cells offers a promising approach to characterising erythropoiesis-related biological responses, yet longitudinal data under real-world training conditions remain limited. This protocol describes the rationale and

Design: of a prospective longitudinal study aimed at investigating erythropoiesis-related transcriptomic adaptations to variations in training load and hypoxic exposure in endurance athletes. A total of 60 trained endurance athletes will be followed over a 12-month period, encompassing baseline conditioning, intensified training phases, competition, recovery, and altitude exposure, where applicable. Training load will be quantified using daily session logs and wearable-derived metrics. Peripheral blood samples will be collected at baseline and monthly intervals, with additional sampling during key physiological phases. Peripheral blood mononuclear cells will undergo transcriptomic profiling using high-throughput gene-expression platforms, with pathway-focused analysis targeting hypoxia signalling, erythroid differentiation, iron metabolism, and angiogenic regulation. Longitudinal statistical modelling will be employed to evaluate adaptation trajectories, intra-individual variability, and associations between transcriptomic responses and quantified training exposures. The study is expected to identify phase-dependent modulation of erythropoiesis-related transcriptional pathways and to enable estimation of physiological ranges of molecular variability across training cycles. Repeated within-individual assessment may provide insight into the persistence and magnitude of transcriptional responses to training stress and hypoxic stimuli. This longitudinal framework is anticipated to generate foundational evidence supporting the feasibility of transcriptomic monitoring in athletic populations and to inform future development of advanced biological surveillance strategies in sport.