title: Effects of High-Intensity Training on Physiological and Hormonal Adaptions in Well-Trained Cyclists.
abstract: 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.
  
  
  
  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.
  
  
  
  INC and MIX achieved >70% of total change in workload eliciting 4 mmol·L [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 < 0.05), and insulin-like growth factor-1 increased by 10% ± 14% (P < 0.05) during weeks 1-4.
  
  
  
  Most of progression in Power4mM, V˙O2peak and peak power output 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 h·wk performing 4 × 16 min work bouts at best effort induces greater adaptions in Power4mM and V˙O2peak than accumulating ~1 h·wk performing best effort intervals as 4 × 4 min.
authors.affiliation: 1Faculty of Health and Sport Sciences, University of Agder, Kristiansand, NORWAY; 2The Norwegian Olympic Federation, Oslo, NORWAY; 3Centre for Elite Sports Research, Department of Neuroscience, Norwegian University of Science and Technology, Trondheim, NORWAY; and 4Section for Sport Science, Lillehammer University College, Lillehammer, NORWAY.
authors.forename: Øystein
authors.initials: Ø
authors.lastname: Sylta
authors.forename: Espen
authors.initials: E
authors.lastname: Tønnessen
authors.forename: Øyvind
authors.initials: Ø
authors.lastname: Sandbakk
authors.forename: Daniel
authors.initials: D
authors.lastname: Hammarström
authors.forename: Jørgen
authors.initials: J
authors.lastname: Danielsen
authors.forename: Knut
authors.initials: K
authors.lastname: Skovereng
authors.forename: Bent R
authors.initials: BR
authors.lastname: Rønnestad
authors.forename: Stephen
authors.initials: S
authors.lastname: Seiler
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D001642:Bicycling / Q000502:physiology*; D015992:Body Mass Index; D005080:Exercise Test; D000072696:High-Intensity Interval Training / Q000379:methods*; D006728:Hormones / Q000097:blood*; D019382:Human Growth Hormone / Q000097:blood; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D011388:Prolactin / Q000097:blood; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism; D013739:Testosterone / Q000097:blood
chemical_list: D006728:Hormones; D018972:Insulin-Like Growth Factor Binding Protein 3; D012738:Sex Hormone-Binding Globulin; D019382:Human Growth Hormone; D013739:Testosterone; D007334:Insulin-Like Growth Factor I; D011388:Prolactin; D006854:Hydrocortisone