Psychophysiological Responses to Repeated-Sprint Training in Normobaric Hypoxia and Normoxia

Purpose: To compare psychophysiological responses to 6 repeated-sprint sessions in normobaric hypoxia (RSH) and normoxia (RSN) in team-sport athletes during a 2-wk "live high-train low" training camp. Methods: While residing under normobaric hypoxia (>= 14 h/d, FiO(2) 14.5-14.2%), 23 lowland elite field hockey players perfollued, in addition to their usual training, 6 sessions (4 x 5 x 5-s maximal sprints, 25-s passive recovery, 5 mm rest) under either RSH (FiO(2) similar to 14.5%) or RSN (FiO(2) 21%). Sprint 1 and 5 times, physiological strain (heart rate [BR], arterial oxyhemoglobin saturation [SpO(2)]), and perceptual responses (overall peripheral discomfort, difficulty breathing, and lower-limb discomfort) were monitored. Results: During the 1st session, HR increased across sets (P <.001) independently of the conditions, while SpO(2) was globally lower (P <.001) for RSH (averaged value: 91.9%+/- 1.2%) vs RSN (96.9% +/- 0.6%). Thereafter, SpO(2) and HR remained similar across sessions for each condition. While 1st-sprint time remained similar, last-sprint time and fatigue index significantly decreased across sets (P <.01) and sessions (P <.05) but not between conditions. Ratings of overall perceived discomfort, difficulty breathing, and lower-limb discomfort were higher (P <.05) in RSH vs RSN at the 1st session. During subsequent sessions, values for overall perceived discomfort (time [P <.001] and condition [P <.05] effects), difficulty breathing (time effect; P <.001), and lower-limb discomfort (condition [P <.001] and interaction [P <.05] effects) decreased to a larger extent in RSH vs RSN. Conclusion: Despite higher hypoxia-induced physiological and perceptual strain during the 1st session, perceptual responses improved thereafter in RSH so as not to differ from RSN. This indicates an effective acclimation and tolerance to this innovative training