Effects of High-Intensity Training on Physiological and Hormonal Adaptions in Well-Trained Cyclists

Purpose: Investigate development of specific performance adaptions and hormonal responses every fourth week during a 12-wk high-intensity training (HIT) period in groups with different interval-training prescriptions. Methods: Sixty-three well-trained cyclists performing a 12-wk intervention consisting of two to three HIT sessions per week in addition to ad libitum low-intensity training. Groups were matched for total training load, but increasing HIT (INC) group (n = 23) performed interval-sessions as 4 × 16 min in weeks 1–4, 4 × 8 min in weeks 5–8, and 4 × 4 min in weeks 9–12. Decreasing HIT (DEC) group (n = 20) performed interval sessions in the opposite order as INC, and mixed HIT (MIX) group (n = 20) performed all interval-sessions in a mixed distribution during 12 wk. Cycling-tests and measures of resting blood hormones were conducted pre, weeks 4, 8, and 12. Results: INC and MIX achieved >70% of total change in workload eliciting 4 mmol·L−1 [la−] (Power4mM) and V˙O2peak during weeks 1–4, versus only 34%–38% in DEC. INC induced larger improvement versus DEC during weeks 1–4 in Power4mM (effect size, 0.7) and V˙O2peak (effect size, 0.8). All groups increased similarly in peak power output during weeks 1–4 (64%–89% of total change). All groups' pooled, total and free testosterone and free testosterone/cortisol ratio decreased by 22% ± 15%, 13% ± 23%, and 14% ± 31% (all P

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