Effect of 4-week intermittent hypoxic exercise training for repeated vertical jump performance in untrained males

BACKGROUND: To be successful in sports, it is critical to maintain a high level of muscular power throughout a game. Physiological adaptations induced by hypoxic exercise training would provide benefits for fatigue-resisting ability during repeated explosive exercise. The aim of this study was to determine whether a 4-week intermittent hypoxic exercise training program is more effective in improving power endurance during repeated vertical jumps (VJs) when compared with a normoxic counterpart. METHODS: Eighteen young adult males were divided into two training groups: 1) normoxic training group (NT, FiO₂: 20.9%, N.=9); and 2) hypoxic training group (HT, FiO₂: 13.7%, N.=9). For both NT and HT, participants performed three sessions per week for four weeks. Each session consisted of a 60-min exercise session including strength and power training. A repeated VJ (40 reps/set, 2 sets with 5 min rest given between them) was performed before and after the training (pretraining and post-training). RESULTS: The HT group displayed an improvement in repeated VJ performance in a later phase of set 1 following the training (25-30 rep: pretraining 26.49±6.20 vs. post-training 30.55±5.37cm, P=0.0285; 30-35 rep: pretraining 25.08±5.29 vs. post-training 29.56±5.37cm, P=0.0064; 35-40 rep: pretraining 25.05±5.51 vs. post-training 29.28±5.71cm, P=0.0161). In set 2, repeated VJ performance in the later phase was also enhanced in HT following the training (P<0.05 for all). No changes in repeated VJ performance were seen in NT following the training (P>0.05 for all). Also, the HT group showed a trend towards a decrease in Fatigue Index in set 1 (pretraining 23.51±13.27 vs. Post 11.87±12.51%, P=0.1308) and set 2 (pretraining 29.11±13.66 vs. post-training 17.81±17.97%, P=0.1588) following the training. CONCLUSIONS: Hypoxic exercise training can be an effective training modality to improve fatigue-resisting ability during repeated explosive exercise.