The Acute Metabolic Effects Of 'Breaking-up' Prolonged Sitting In Adults

Recent epidemiological studies suggest that regularly 'breaking up' sedentary (sitting) time, even with short duration, light-intensity activities, is beneficially associated with several cardio-metabolic biomarkers. However, intervention studies are required to better understand this association, and, in particular, to investigate causality. PURPOSE: To compare the effects of a single prolonged (7-hour) bout of sitting on post-prandial glucose and insulin levels with a similar duration of sitting combined with intermittent bouts of light-intensity or moderate-intensity activity in 19 overweight/obese adults (age range 45-65 yrs) without diabetes. METHODS: In a randomized Latin-square design trial, each participant completed three 7-hour experimental conditions over three separate weeks: 1) prolonged sitting: reclined position with no activity; 2) prolonged sitting + light-intensity activity: reclined seating interspersed with 2-minute bouts of light-intensity treadmill walking at 3.2 km/hr every 20 minutes; and 3) prolonged sitting + moderate-intensity activity: reclined seating interspersed with 2-minute bouts of moderate-intensity treadmill walking at between 5.8-6.4 km/hr every 20 minutes. A standard test meal (75 g glucose, 50 g fats) was given 2 hours post-baseline measurements, and blood samples were obtained hourly over the remaining 5 hours to calculate the incremental area under the curve (iAUC - Mean ± SEM). GEE models were adjusted for sex, treatment order and pre-prandial values. RESULTS: The glucose iAUC (mmol/l/hr) following both light and moderate-intensity activity conditions was similarly and significantly reduced (light: 15.6 ± 2.9; p=0.002; moderate: 15.1 ± 2.9; p < 0.001) compared to prolonged sitting (17.7 ±3.3). Insulin iAUC (mU/l/hr) was also significantly reduced with both activity conditions (light: 122.6 ± 9.0, p = 0.001; moderate: 122.8 ± 9.1, p = 0.001) compared to prolonged sitting (152.1 ± 11.2). No significant differences were observed between the two activity conditions. CONCLUSION: These findings indicate that the acute post-prandial glucose and insulin responses during prolonged sitting can be attenuated by intermittent short bouts of either light or moderate-intensity physical activity. Supported by NHMRC Project Grant 540107.