Extremely short duration high intensity interval training substantially improves insulin action in young healthy males

TLDR

Traditional high‑volume aerobic training lowers cardiovascular and metabolic disease risk but requires a substantial time commitment. This study examined whether a very low‑volume high‑intensity interval training program can improve insulin action and glycemic control in young healthy men. Participants completed six supervised 30‑second sprint sessions over two weeks (≈15 min total, ≈250 kcal/week), and pre‑ and post‑training aerobic performance and 75‑g OGTT responses were measured. After two weeks of HIT, glucose, insulin and NEFA area‑under‑curve responses fell by 12%, 37% and 26% respectively, insulin sensitivity rose 23%, and cycling performance improved 6%, demonstrating that ~250 kcal/week of high‑intensity exercise markedly enhances insulin action.

Abstract

Traditional high volume aerobic exercise training reduces cardiovascular and metabolic disease risk but involves a substantial time commitment. Extremely low volume high-intensity interval training (HIT) has recently been demonstrated to produce improvements to aerobic function, but it is unknown whether HIT has the capacity to improve insulin action and hence glycemic control.Sixteen young men (age: 21 +/- 2 y; BMI: 23.7 +/- 3.1 kg x m-2; VO2peak: 48 +/- 9 ml x kg-1 x min-1) performed 2 weeks of supervised HIT comprising of a total of 15 min of exercise (6 sessions; 4-6 x 30-s cycle sprints per session). Aerobic performance (250-kJ self-paced cycling time trial), and glucose, insulin and NEFA responses to a 75-g oral glucose load (oral glucose tolerance test; OGTT) were determined before and after training.Following 2 weeks of HIT, the area under the plasma glucose, insulin and NEFA concentration-time curves were all reduced (12%, 37%, 26% respectively, all P < 0.001). Fasting plasma insulin and glucose concentrations remained unchanged, but there was a tendency for reduced fasting plasma NEFA concentrations post-training (pre: 350 +/- 36 v post: 290 +/- 39 micromol x l-1, P = 0.058). Insulin sensitivity, as measured by the Cederholm index, was improved by 23% (P < 0.01), while aerobic cycling performance improved by approximately 6% (P < 0.01).The efficacy of a high intensity exercise protocol, involving only ~250 kcal of work each week, to substantially improve insulin action in young sedentary subjects is remarkable. This novel time-efficient training paradigm can be used as a strategy to reduce metabolic risk factors in young and middle aged sedentary populations who otherwise would not adhere to time consuming traditional aerobic exercise regimes.