Effects of 5-Wk Repeated Sprint Training in Hypoxia on Global Inspiratory and Core Muscle Functions

Repeated-sprint training in hypoxia (RSH) has been shown to boost team-sport players' repeated-sprint ability (RSA). Whether players' global inspiratory muscle (IM) and core muscle (CM) functions would be altered concomitantly with RSH was not reported. This study was designed to compare the concomitant alternations in players' RSA and their IM and CM functions during a team-sport-specific intermittent exercise protocol (IEP) before and after the intervention. Twenty players were assigned into either RSH or control (CON) groups (n = 10 for each). RSH players participated in 5-wk RSH (15 sessions, 3 sets 5x5-s all-out treadmill sprints interspersed with 25-s passive recovery under the hypoxia of 13.5%) while CON players had no corresponding training. The changes in RSA between pre- and post-intervention, and the alterations in IM and CM functions that were revealed by maximum inspiratory mouth pressure (PI_max) and sport-specific endurance plank test (SEPT) performance, respectively, between pre- and post-IEP and across pre- and post-intervention in the RSH group were compared with that of CON. Following the 5-wk RSH, players' RSA improved significantly (>6%, p < 0.05) while PI_max and SEPT performance did not alter (P > 0.05). Nevertheless, PI_max which declined markedly in pre-intervention IEP (pre-IEP 155.4 ± 22.7 vs post-IEP 140.6 ± 22.8 cmH₂O, p < 0.05) was alleviated significantly in post-intervention IEP (152.2 ± 27.4 vs 152.6 ± 31.8, p > 0.05), while the concomitant declined SEPT performance in the pre-intervention IEP (155 ± 24.6 vs 98.1 ± 21.7 s, p < 0.05) was retained post intervention (170.7 ± 38.1 vs 100.5 ± 33.4, p < 0.05). For the CON, all variables were unchanged (p > 0.05). Such findings suggest that 5-wk RSH could enhance players' RSA but not global IM and CM functions. Nonetheless, the decline in PI_max in pre-intervention IEP alleviated significantly post intervention led to a postulation that players' IM endurance, rather than strength, might improve with the 5-wk RSH regimen, while the possible improved IM endurance did not advance the fatigue resistance of CM.