High intensity interval exercise is an effective alternative to moderate intensity exercise for improving glucose tolerance and insulin sensitivity in adolescent boys

Objectives: High-intensity interval exercise (HIIE) may offer a time efficient means to improve health outcomes compared to moderate-intensity exercise (MIE). This study examined the acute effect of HIIE compared to a work-matched bout of MIE on glucose tolerance, insulin sensitivity (IS), resting fat oxidation and exercise enjoyment in adolescent boys. Design: Within-measures design with counterbalanced experimental conditions. Methods: Nine boys (14.2 +/- 0.4 years) completed three conditions on separate days in a counterbalanced order: (1) HIIE; (2) work matched MIE, both on a cycle ergometer; and (3) rest (CON). An oral glucose tolerance test (OGTT) was performed after exercise or rest and the area under curve (AUC) responses for plasma [glucose] and [insulin] were calculated, and IS estimated (Cederholm index). Energy expenditure and fat oxidation were measured following the OGTT using indirect calorimetry. Exercise enjoyment was assessed using the Physical Activity Enjoyment Scale. Results: The incremental AUC (iAUC) for plasma [glucose] was reduced following both MIE (-23.9%, P=0.013, effect size [ES] = -0.64) and HIIE (-28.9%, P=0.008, ES = -0.84) compared to CON. The iAUC for plasma [insulin] was lower for HIIE (-24.2%, P= 0.021, ES = -0.71) and MIE (-29.1%, P= 0.012, ES = -0.79) compared to CON. IS increased by 11.2% after HIIE (P= 0.03, ES = 0.76) and 8.4% after MIE (P= 0.10, ES=0.58). There was a trend for an increase in fat oxidation following HIIE (P= 0.097, ES = 0.70). Both HIIE and MIE were rated as equally enjoyable (P > 0.05, ES < 0.01). Conclusion: A single bout of time efficient HIIE is an effective alternative to MIE for improving glucose tolerance and IS in adolescent boys immediately after exercise. (C) 2014 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.