Repeated-sprint training in hypoxia boosts up team-sport-specific repeated-sprint ability: 2-week vs 5-week training regimen

Purpose: To investigate (1) the boosting effects immediately and 4 weeks following 2-week, 6-session repeated-sprint training in hypoxia (RSH_2-wk, n = 10) on the ability of team-sport players in performing repeated sprints (RSA) during a team-sport-specific intermittent exercise protocol (RSA_IEP) by comparing with normoxic counterpart (CON_2-wk, n = 12), and (2) the dose effects of the RSH by comparing the RSA alterations in RSH_2-wk with those resulting from a 5-week, 15-session regimen (RSH_5-wk, n = 10). Methods: Repeated-sprint training protocol consisted of 3 sets, 5 × 5-s all-out sprints on non-motorized treadmill interspersed with 25-s passive recovery under the hypoxia of 13.5% and normoxia, respectively. The within- (pre-, post-, 4-week post-intervention) and between- (RSH_2-wk, RSH_5-wk, CON_2-wk) group differences in the performance of four sets of RSA tests held during the RSA_IEP on the same treadmill were assessed. Results: In comparison with pre-intervention, RSA variables, particularly the mean velocity, horizontal force, and power output during the RSA_IEP enhanced significantly immediate post RSH in RSH_2-wk (5.1–13.7%), while trivially in CON_2-wk (2.1–6.2%). Nevertheless, the enhanced RSA in RSH_2-wk diminished 4 weeks after the RSH (− 3.17–0.37%). For the RSH_5-wk, the enhancement of RSA immediately following the 5-week RSH (4.2–16.3%) did not differ from that of RSH_2-wk, yet the enhanced RSA was well-maintained 4-week post-RSH (0.12–1.14%). Conclusions: Two-week and five-week RSH regimens could comparably boost up the effects of repeated-sprint training in normoxia, while dose effect detected on the RSA enhancement was minimal. Nevertheless, superior residual effects of the RSH on RSA appear to be associated with prolonged regimen.