No acute effect of reduced-exertion high-intensity interval training on insulin sensitivity

We have previously demonstrated that reduced-exertion high-intensity interval training (REHIT), requiring a maximum of two 20-s all out cycling sprints in a 10-min exercise session, improves insulin sensitivity in sedentary men over a 6-week training intervention. However, the acute effects of REHIT on insulin sensitivity have not previously been described. In this study fourteen men and women (mean±SD age: 23±5 y; BMI 22.7±4.7 kg•m-2; V̇O2max: 37.4±8.6 mL•kg-1•min-1) underwent oral glucose tolerance testing 14-16 hours after an acute bout of reduced-exertion high-intensity interval training (2 x 20-s all-out sprints; REHIT), moderate-vigorous aerobic exercise (45 minutes at ~75% VO2max; AER), and a resting control condition (REST). Neither REHIT nor AER were associated with significant changes in glucose AUC (REHIT 609±98 vs. AER 651±85 vs. REST 641±126 mmol•l-1•120 min), insulin AUC (REHIT 30.9±15.4 vs. AER 31.4±13.0 vs. REST 35.0±18.5 nmol•l-1•120 min) or insulin sensitivity estimated by the Cederholm index (REHIT 86±20 vs. AER 79±13 vs. REST 82±24 mg•l2•mmol-1•mU-1•min-1). These data suggest that improvements in insulin sensitivity following a chronic REHIT intervention are the result of training adaptations rather than acute effects of the last exercise session.