Effects of HIT on Physiological and Hormonal Adaptions in Well-Trained Cyclists.

Research paper by Øystein Ø Sylta, Espen E Tønnessen, Øyvind Ø Sandbakk, Daniel D Hammarström, Jørgen J Danielsen, Knut K Skovereng, Bent R BR Rønnestad, Stephen S Seiler

Indexed on: 26 Jan '17Published on: 26 Jan '17Published in: Medicine and science in sports and exercise


Investigate development of specific performance adaptions and hormonal responses every 4 week during a 12-week HIT period in groups with different interval-training prescriptions.Sixty-three well-trained cyclists performing a 12-week intervention consisting of 2-3 HIT sessionsweek 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 4x16 min in week 1-4, 4x8 min in week 5-8 and 4x4 min in week 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 weeks. Cycling-tests and measures of resting blood-hormones were conducted pre, week 4, 8 and 12.INC and MIX achieved >70% of total change in workload eliciting 4 mMolL [la] (Power4mM) and V˙ O2peak during week 1-4, versus only 34-38% in DEC. INC induced larger improvement vs. DEC during week 1-4 in Power4mM (ES: 0.7) and V˙ O2peak (ES: 0.8). All groups increased similarly in peak power output (PPO) during week 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<0.05), and insulin-like growth factor-1 increased by 10±14% (P<0.05) during week 1-4.Most of progression in Power4mM, V˙ O2peak and PPO was achieved during weeks 1-4 in INC and MIX, and accompanied by changes in resting blood-hormones consistent with increased but compensable stress load. In these well-trained subjects, accumulating 2-3 hweek performing 4x16 min work bouts at best effort induces greater adaptions in Power4mM and V˙ O2peak than accumulating ~1 hweek performing best effort intervals as 4×4 min.