Ingvill Odden, Håvard Hamarsland, Tomas Urianstad Odden, Daniel Hammarström, Anne Mette Rustaden, Lise Koll, Marita Hanestadhaugen, Steen Larsen, Stian Ellefsen, Joar Hansen, Håvard Nygaard, Carsten Lundby, Knut Sindre Mølmen
Repeating the same exercise training intervention within the same individuals after an adequate detraining period provides a direct test of whether physiological adaptations are reproducible within individuals. This study demonstrates that individual physiological adaptations to a repeated endurance training program are largely nonreproducible across multiple physiological and performance outcomes, despite highly standardized and closely supervised training conditions. The substantial within-individual response variability challenges the notion that physiological training responsiveness is a stable, trait-like characteristic.