Abstract
PURPOSE To compare the metabolic effects of breaking up sedentary time with prolonged periods of standing versus multiple shorter standing bouts with the same total duration to determine whether, in principle, altering the frequency of "standing breaks" in sedentary time, influences metabolic responses over the course of the day. METHODS Ten normoglycemic overweight/obese men (age, 33 ± 13 yr; body mass index, 28.3 ± 3.0 kg·m; mean ± SD) each participated in three experimental trials in random order, in which they arrived fasted, then consumed a test breakfast (8 kcal·kg body weight, with 37% energy from fat, 49% from carbohydrates, 14% from protein) and, 4 h later, an identical test lunch. Expired air and blood samples were taken fasted and for 8 h postprandially. In one trial (uninterrupted sitting), participants sat continuously throughout the observation period; in the prolonged standing (PRO-Stand) trial, participants stood still for 15 min every 30 min; and in the intermittent standing trial (INT-Stand), they stood for 1.5 min, 10 times every 30 min. RESULTS Compared with uninterrupted sitting, energy expenditure was 320 ± 62 kJ (10.7% ± 2.0%) higher in PRO-Stand and 617 ± 76 kJ (20.4% ± 2.3%) higher in INT-Stand: energy expenditure in INT-Stand was 296 ± 78 kJ (9.0% ± 2.3%) higher than PRO-Stand (mean ± SEM; all P < 0.001). However, there were no significant differences between trials in postprandial glucose, insulin, or triglyceride responses. CONCLUSIONS These data demonstrate an independent effect of frequency of sedentary breaks on energy expenditure which provides an explanation for the association between frequency of sedentary breaks and adiposity observed in epidemiological data. However, it may be necessary to break up sitting with activities of greater intensity than quiet standing to positively influence glucose, insulin, and triglyceride metabolism in relatively young, normoglycemic, overweight/obese men.
