Effects of different periods of hypoxic training on glucose metabolism and insulin sensitivity

Abstract

This study examined the effects of different periods of hypoxic training on glucose metabolism. Sedentary subjects underwent hypoxic training (FiO2 = 15.0%) for either 2 weeks (2-week group; n = 11) or 4 weeks (4-week group; n = 10). The 2-week group conducted training sessions on 6 days week(-1) for 2 weeks, whereas the 4-week group conducted training sessions on 3 days week(-1) for 4 weeks. Body fat mass or abdominal fat area did not change after training period in either group. VO2max increased in both groups after training period (42 ± 2 versus 43 ± 2 ml min(-1) kg(-1) in 2-week group, 41 ± 1 versus 42 ± 2 ml min(-1) kg(-1) in 4-week group). Both groups showed a reduction in mean blood pressure after training period (92 ± 3 versus 90 ± 3 mmHg in 2-week group, 91 ± 2 versus 87 ± 2 mmHg in 4-week group, P ≤ 0.05). No change was observed in blood glucose response after glucose ingestion after training period. However, area under the curve for serum insulin concentrations after glucose ingestion significantly decreased in only 4-week group (6910 ± 763 versus 5812 ± 872 μIU ml(-1) 120 min, P ≤ 0.05). In conclusion, hypoxic training reduced blood pressure with independent on training duration. However, a longer period of hypoxic training led to greater improvements in insulin sensitivity compared with equivalent training over a shorter period, suggesting that hypoxic training programmes for more than 4 weeks might be more beneficial for improving insulin sensitivity.

Keywords: endurance training; insulin sensitivity; length of training period; normobaric hypoxia; short-term training.