Energy Cost Of Selected Supine, Sitting, And Standing Sedentary Behaviors In Adults

Abstract

Sedentary behaviors are persuasive in all societies. According to the 2018 American Time Use Survey, nearly 96% of adults spend 4-5 hours/day in sedentary behaviors that include watching TV, reading, computer use, relaxing and thinking. Since sedentary behaviors increase chronic disease risks, interest is high in knowing the energy costs of sedentary behaviors to help populations to reduce time spent in sedentary behaviors. PURPOSE: To update the energy costs of sedentary behaviors in the 2011 Adult Compendium of Physical Activities. METHODS: Energy cost in ml.kg-1.min-1 and heart rate in b.min-1 were measured by Cosmed K4b2 portable indirect calorimetry system in 10 males and 9 females (20-59y), mean age (31.6 ± 7.5 y), weight (63.4 ± 8.9 kg), and height (167.1 ± 5.8 cm). The subjects completed 17 randomly assigned behaviors in lying, reclining, sitting, and standing positions (doing nothing, watching TV, reading, writing, texting, typing, fidgeting) for 5 min with a 2 min rest between behaviors. Mean ± SD were computed with data presented as mean METs computed as VO2 ml.kg-1.min-1 / 3.5 ml.kg-1.min-1. Terminal digits for MET values were rounded to 0, 3, 5, or 8 to comply with format of the Compendium. RESULTS: Mean MET values are presented by behaviors and postures performed. Doing nothing (lie: 1.3, sit: 1.3. stand: 1.0); Watching TV (lie: 1.3, sit: 1.3); Reading (recline; 1.5, sit: 1.0); Writing (recline: 1.5, sit: 1.3, stand: 1.3); Texting (recline: 1.3, sit: 1.0, stand: 1.0); Fidgeting (sit hands only: 1.5, sit feet only: 1.8, stand hands & feet: 2.0); Typing (stand: 1.3). Of the measured MET values, seven were the same as the Compendium, four were lower (on the order of 0.3 to 0.8 METs), and one was higher by 0.3 METs (Recline: read). Heart rates during the behaviors ranged from 62 to 80 beats.min-1. CONCLUSIONS: The measured mean MET values ranged from 1.0 to 2.0 METs, classified as inactive (1.0-1.49 METs) and light activity (1.5-2.9 METs). Duplication of measured MET values to those in the Compendium confirm the energy cost of common sedentary behaviors. Of the four behaviors with lower measured MET values, three had been estimated in the Compendium (Sit: read, text; Stand text). Four behaviors not in the 2011 Compendium were measured (Recline: write, text; Stand: write, text). Supported by the Shanghai University of Sport