The Interval Pattern, Rather than High Intensity, Accounts for the Superior Effects of High-Intensity Interval Exercise (HIIE) on Glucose Tolerance.

PURPOSE: Some data suggest that high-intensity interval exercise improves glycemic control more than continuous exercise. We aimed to identify the factor(s) that enhance insulin sensitivity during an oral glucose tolerance test (OGTT) after exercise.

METHODS

Ten healthy, physically active individuals (including three females) completed three work-matched 50-minute exercise trials that differed in workload distribution. Using a randomized crossover design, participants completed: a) a moderate-intensity continuous exercise trial (MICE), b) a high-intensity interval exercise trial (HIIE), c) a high-intensity continuous exercise trial (HICE), and d) a no-exercise control trial (CONT). After exercise, insulin sensitivity (IS MATSUDA) was measured during the OGTT. Plasma glucose kinetics and oxidation rates were measured by infusion of isotopically labeled [U- 13C] glucose. Glycogen oxidation was calculated as the difference between total carbohydrate oxidation (assessed by indirect calorimetry) and plasma glucose oxidation.

RESULTS

Total carbohydrate oxidation, plasma glucose oxidation, calculated glycogen oxidation, and plasma lactate accumulation during exercise were similar between HIIE and HICE, and both were higher than during MICE (p<0.05). Only HIIE decreased the postprandial insulin area under the curve, which increased IS MATSUDA index above CONT, MICE and HICE (15.5±4.3 vs.12.7±4.4; 12.5±6.1 and 11.8±6.0; p = 0.048, 0.030, 0.005, respectively).

CONCLUSIONS

In summary, improvements in glycemic control following HIIE seem to be more related to its cyclic pattern than to glycogen use during the high-intensity segments. Our data suggest that exercise programs aimed at restoring glycemic control should emphasize workload cycling before engaging the high-intensity component.