Molecular and Physiological Adaptations to Seasonal Training in Elite U18 Ice Hockey Players

TL;DR

This study explores how elite U18 ice hockey players adapt to seasonal training by measuring changes in aerobic capacity and molecular markers like irisin and cell-free DNA.

Contribution

The study provides preliminary longitudinal evidence of chronic irisin elevation in youth ice hockey players and suggests combining molecular and physiological markers for training monitoring.

Findings

VO2max and irisin levels increased significantly from pre- to early-season in elite U18 ice hockey players.

Cell-free DNA decreased moderately, while cortisol levels remained stable during the training period.

Inter-individual variability in VO2max and irisin increased, while variability in cfDNA decreased significantly.

Abstract

Monitoring adolescent team-sport athletes may benefit from combining performance and molecular markers, but empirical evidence supporting this approach in youth team sports remains limited. Objective: Our study investigated molecular and physiological adaptations to seasonal training in elite U18 ice hockey players, focusing on aerobic capacity, salivary cortisol, serum irisin, and cell-free DNA (cfDNA) dynamics. Methods: National-level U18 players were enrolled in our study (n = 23 for cross-sectional analysis, n = 12 longitudinal) during the pre- and early-competition season. Aerobic performance was assessed via graded treadmill VO2max testing, and the biochemical markers quantified using ELISA-based assays. Results: From pre- to early-season (paired n = 12), VO2max increased by 10.6% (g = +1.00, p = 0.003) and irisin by 14.7% (g = +0.83, p = 0.010). cfDNA decreased by 60.8% (g = −0.54, p = 0.070; moderate effect, not statistically clear), while cortisol remained stable (+11.3%; p = 0.667). Inter-individual variability increased for VO2max and irisin and decreased by 82% for cfDNA. Exploratory cross-sectional positional analysis indicated higher irisin levels in forwards and elevated cfDNA in defensemen, although differences did not reach statistical significance. Conclusions: These preliminary findings provide cohort-size limited longitudinal evidence of chronic irisin elevation in ice hockey players and highlight the possibility of combining VO2max + irisin + cfDNA to assist individualized load/recovery in elite youth ice hockey.

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