Low-volume high-intensity interval training rapidly improves cardiopulmonary function in postmenopausal women

Objective: This study compared the effects of a 2-week program of low-volume high-intensity interval training (HIT) with the effects of higher-volume moderate-intensity continuous training (CT) on cardiopulmonary and vascular functions in postmenopausal women. Methods: Twenty-two postmenopausal women were randomly assigned to undertake six HIT (n = 12) or CT (n = 10) sessions for 2 weeks. HIT sessions consisted of ten 1-minute intervals of cycling exercise at 100% of peak power output separated by 1 minute of active recovery. CT sessions involved 40 minutes of continuous cycling at 65% of peak power output. Variables assessed at baseline and 2 weeks included cardiopulmonary function (ventilatory threshold, peak oxygen uptake), macrovascular endothelial function (flow-mediated dilation of the brachial artery), and microvascular function (reactive hyperemia and local thermal hyperemia of forearm skin). Results: Eighteen participants completed the study (HIT, 11; CT, 7). Adherence to the exercise programs was excellent, with 107 of 108 sessions completed. Despite substantially lower total time commitment (~2.5 vs ~5h) and training volume (558 vs 1,237 kJ) for HIT versus CT, increases from baseline in peak oxygen uptake achieved significance (P = 0.01) for the HIT group only ([DELTA = 2.2 mL kg-1 min -1; P for interaction = 0.688). Improvements in exercise test duration were observed in both groups (HIT, 13%; CT, 5%; P for interaction = 0.194). There were no significant changes in macrovascular or microvascular function in either group. Conclusions: The findings suggest that low-volume HIT is feasible and can lead to rapid improvements in cardiopulmonary function in postmenopausal women.