Breaking sitting time with physical activity increases energy expenditure but does not alter postprandial metabolism in girls

Purpose: Young people spend a substantial proportion of their time at school sedentary; therefore, this setting represents an important target for interventions aimed at displacing sedentary time with physical activity. This study aimed to examine the postprandial metabolic effects of breaking sedentary time by accumulating walking and repeated bouts of nonambulatory standing during simulated school days in inactive adolescent girls.

Methods: Seventeen girls (12.8 (0.4) years) completed two 3-day experimental conditions. On Day 1 and 2 of the standing + walking (STD-WLK) experimental trial, participants interrupted sedentary time by completing 4 x 10 min bouts of self-paced walking and accumulated 18 x 5 min standing bouts during each simulated school day. On Day 3 of STD-WLK, participants attended school as normal with no additional physical activity or standing prescribed. On all 3 days of the control condition (CON), participants attended school as normal with no physical activity intervention. On Day 2 and 3 of both STD-WLK and CON, a baseline capillary blood sample was provided to determine fasting [TAG] and [glucose]. Participants then consumed a standardised breakfast (0 h) and lunch (4.7 h) and blood samples were provided postprandially at 2.7, 5.3 and 7.3 h for [TAG] and [glucose].

Results: Energy expenditure was 28% (95% CI = 8 to 52%) higher during school hours on Day 1 and Day 2 during STD-WLK compared with CON (2171 vs. 1693 kJ; ES = 0.89, P = 0.008). However, no reduction of fasting or postprandial [TAG] or [glucose] was observed on Day 2 or 3 (P≥0.245). 

Conclusions: Two-consecutive days of breaking prolonged sitting with self-paced walking and intermittent standing had no meaningful effect on postprandial metabolism in adolescent girls.