Effect of high-intensity resistance circuit-based training in hypoxia on aerobic performance and repeat sprint ability

Recent acute studies have shown that high-intensity resistance circuit-based (HRC) training in hypoxia increases metabolic stress. However, no intervention studies have yet proven their effectiveness. This study aimed to analyze the effect of 8 weeks of HRC in hypoxia on aerobic performance, resting energy expenditure (REE), repeat sprint ability (RSA) and hematological variables. Twenty-eight subjects were assigned to hypoxia (FiO₂ = 15%; HRC_hyp : n = 15; age: 24.6 ± 6.8 years; height: 177.4 ± 5.9 cm; weight: 74.9 ± 11.5 kg) and normoxia (FiO₂ = 20.9%; HRC_norm : n = 13; age: 23.2 ± 5.2 years; height: 173.4 ± 6.2 cm; weight: 69.4 ± 7.4 kg) groups. Each training session consisted of two blocks of three exercises (Block 1: bench press, leg extension, front pull down; 2: deadlift, elbow flexion, ankle extension). Each exercise was performed at 6 repetitions maximum. Participants exercised twice weekly for 8 weeks and before and after the training program blood test, REE, RSA and treadmill running test were performed. Fatigue index in the RSA test was significantly decreased in the HRC_hyp (-0.9%; P < .01; ES = 2.75) but not in the HRC_norm . No changes were observed in REE and hematological variables. Absolute (4.5%; P = .014; ES = 0.42) and relative (5.2%; P = .008; ES = 0.43) maximal oxygen uptake (VO₂ max), speed at VO₂ max (4%; P = .010; ES = 0.25) and time to exhaustion (4.1%; P = .012; ES = 0.26) were significantly increased in HRC_hyp but not in the HRC_norm . No significant differences between groups were found. Compared with normoxic conditions, 8 weeks of HRC training under hypoxic conditions efficiently improves aerobic performance and RSA without changes in REE and red blood O₂ -carrying capacity.