title: Team-Sport Athletes' Improvement of Performance on the Yo-Yo Intermittent Recovery Test Level 2, but Not of Time-Trial Performance, With Intermittent Hypoxic Training.
abstract: OBJECTIVE
  To determine the time course for physical-capacity adaptations to intermittent hypoxic training (IHT) in team-sport athletes and the time course for benefits remaining after IHT.
  
  
  METHODS
  A pre-post parallel-groups design was employed, with 21 Australian footballers assigned to IHT (n = 10) or control (CON; n = 11) matched for training load. IHT performed eleven 40-min bike sessions at 2500-m altitude over 4 wk. Yo-Yo Intermittent Recovery Test level 2 (Yo-Yo IR2) was performed before; after 3, 6, and 11 IHT sessions; and 30 and 44 d after IHT. Repeated time trials (2- and 1-km TTs, with 5 min rest) were performed before, after, and 3 wk after IHT. Hemoglobin mass (Hb(mass)) was measured in IHT before and after 3, 6, 9, and 11 sessions.
  
  
  RESULTS
  Baseline Yo-Yo IR2 was similar between groups. After 6 sessions, the change in Yo-Yo IR2 in IHT was very likely higher than CON (27% greater change, effect size 0.77, 90% confidence limits 0.20;1.33) and likely higher 1 d after IHT (23%, 0.68, 0.05;1.30). The IHT group's change remained likely higher than CON 30 d after IHT (24%, 0.72, 0.12;1.33) but was not meaningfully different 44 d after (12%, 0.36, -0.24;0.97). The change in 2-km TT performance between groups was not different throughout. For 1-km TT, CON improved more after IHT, but IHT maintained performance better after 3 wk. Hb(mass) was higher after IHT (2.7%, 0.40, -0.40;1.19).
  
  
  CONCLUSIONS
  Short-duration IHT increased Yo-Yo IR2 compared with training-load-matched controls in 2 wk. An additional 2 wk of IHT provided no further benefit. These changes remained until at least 30 d posttraining. IHT also protected improvement in 1-km TT.
authors.affiliation: Inst of Sport, Exercise and Active Living, Victoria University, Melbourne, VIC, Australia.
authors.forename: W H
authors.initials: WH
authors.lastname: Inness M
authors.forename: François
authors.initials: F
authors.lastname: Billaut
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Aughey
mesh_terms: D000222:Adaptation, Physiological; D000531:Altitude; D054874:Athletic Performance / Q000502:physiology*; D001315:Australia; D005080:Exercise Test; D006801:Humans; D000860:Hypoxia / Q000097:blood; D008297:Male; D010806:Physical Education and Training / Q000379:methods*