The Combined Effects Of Regular Activity Breaks And Physical Activity On Postprandial Metabolism

Regularly interrupting sedentary behavior with short bouts of activity lowers postprandial glycemia, however, the effects on lipid responses are inconsistent. Additionally, little is known about how the effects of regular activity breaks and continuous physical activity may combine to affect postprandial metabolism. PURPOSE: To compare the effects of prolonged sitting and regular activity breaks with or without 30 min of continuous physical activity on postprandial metabolism. METHODS: A randomized, crossover study was conducted; 36 adults (mean age 25 y (SD 3.9), BMI 23.9 (SD 3.9), VO2max 36.2 (SD 9.2) mL·kg·min-1) completed the following four two-day interventions: Prolonged sitting on both days, without (SED+SED) or with (PA+SED) a 30 min bout of continuous walking (60% VO2max) at the end of day 1; sitting on both days interrupted with regular activity breaks (2 min walking every thirty minutes at 60% VO2max), without (RAB+RAB) or with (PA+RAB) a 30 min bout of continuous walking (60% VO2max) at the end of day 1. Postprandial metabolic responses to a standardized test meal (0.71 g/kg CHO, 0.70 g/kg FAT, 0.32 g/kg PRO, 43.24 kJ/kg) were measured in venous blood samples over 5h on day 2 - at baseline, 30 and 45 min, and then hourly. Plasma glucose, insulin, and triglycerides were used to calculate total area under the response curve (AUC). Mixed model regression was used to compare the effects of interventions on AUC. RESULTS: There was no effect of intervention on glucose AUC (p=0.26). Compared to SED+SED, insulin AUC was significantly lower in PA+SED (-15%; 95% CI -4, -24%; p=0.01), RAB+RAB (-11%; 95% CI 0, -20%; p=0.05) and PA+RAB (-23%; -12, -31%; p<0.001). PA+RAB lowered insulin AUC more than PA+SED (-13%; 95% CI -4, -22%; p=0.01). Neither PA+SED nor RAB+RAB alone affected triglyceride AUC. However, PA+RAB significantly lowered triglyceride AUC compared to both SED+SED (-0.74 mmol·L-1·5h; 95% CI -1.28, -0.20; p=0.01) and PA+SED (-0.67 mmol·L-1·5h; 95% CI -1.15, -0.19; p=0.01). CONCLUSIONS: The results indicated that all patterns of physical activity cause an acute improvement in insulin sensitivity. Regular activity breaks and physical activity combined provides the greatest improvements in insulin sensitivity, while also lowering postprandial lipids. Support: Heart Foundation, Lotteries, & University of Otago.