The Effect Of 5-week Intermittent Hypoxia Resistance Training On Hormones And Muscle Strength In Males

The effects of different levels of systemic hypoxia on hormonal responses, strength and body composition to 5-week resistance training were investigated. Twenty-five male subjects were randomly assigned into 3 experimental groups that performed 10 sessions (2X5 weeks) of barbell back squat (10 reps,5 sets,70% 1RM) under normoxia (NR, FiO2=21%) and hypoxia (HL, FiO2=16%; HH, FiO2=12.6%). Serum growth hormone (GH), testosterone (T) and cortisol (C) concentrations were measured before (Pre) and at 0 (T-0),15 (T-15),30 (T-30) min after exercise in the first and last training sessions.1RM, isometric knee extension (KE), isometric leg presses (LP) and body composition were evaluated before and after the protocol. In the first session, GH of HH (p<0.01) and HL (p<0.01) was higher than NR at T-0. In the last session, GH of HH was higher than NR at T-0 (p<0.05); meanwhile, T/C ratio of HH was higher than NR at Pre (p<0.01), T-0 (p<0.01) and T-15 (p<0.05). Following the training protocol, HH showed greater (p<0.05) improvement on LP compared with NR; lean body mass (LBM) was increased in hypoxia groups only. Moderate intensity resistance training performed in severe hypoxia (FiO2=12.6%) induced greater GH responses and isometric strength gains in leg press than that in normoxia. Both hypoxia groups showed improved strength and body composition following training. However, no significant difference was observed between the two levels of hypoxia used in the current study. FiO2 of 12.6% was recommended when performing the moderate intensity resistance training under systemic hypoxia.