Heterogeneity in the Energy Cost of Posture Maintenance during Standing Relative to Sitting: Phenotyping According to Magnitude and Time-Course

Abstract

BackgroundReducing sitting-time may decrease risk of disease and increase life-span. In the search for approaches to reduce sitting-time, research often compares sitting to standing and ambulation, but the energetic cost of standing alone versus sitting is equivocal, with large variation in reported mean values (0% to >20% increase in energy expenditure (EE) during standing).ObjectiveTo determine the magnitude and time-course of changes in EE and respiratory quotient (RQ) during steady-state standing versus sitting.DesignMin-by-min monitoring using a posture-adapted ventilated-hood indirect calorimetry system was conducted in 22 young adults with normal BMI during 10 min of steady-state standing versus sitting comfortably.ResultsThis study reveals three distinct phenotypes based on the magnitude and time-course of the EE response to steady-state standing. One-third of participants (8/22) showed little or no change in EE during standing relative to sitting (ΔEE <5%; below first quartile). Of the 14 responders (ΔEE 7–21%), 4 showed sustained, elevated EE during standing, while 10 decreased their EE to baseline sitting values during the second half of the standing period. These EE phenotypes were systematically mirrored by alterations in RQ (a proxy of substrate oxidation), with ΔEE inversely correlated with ΔRQ (r = 0.6–0.8, p<0.01).ConclusionThis study reveals different phenotypes pertaining to both energy cost and fuel utilization during standing, raising questions regarding standing as a strategy to increase EE and thermogenesis for weight control, and opening new avenues of research towards understanding the metabolic and psychomotor basis of variability in the energetics of standing and posture maintenance.

Standing economy: does the heterogeneity in the energy cost of posture maintenance reside in differential patterns of spontaneous weight-shifting?

“…The sample size for Study I was calculated using an online calculator (http://www.statisticalsolutions.net/calculators.php) and data obtained from previous investigations by our laboratory (Miles-Chan et al 2013;Monnard and Miles-Chan 2017). As Studies Ib and II were exploratory studies, no data previous data were available to conduct a priori sample size calculations.…”

“…As Studies Ib and II were exploratory studies, no data previous data were available to conduct a priori sample size calculations. Study III was designed to have sufficient power (α = 0.05, β > 80%) to detect a 50% increase in EE relative to resting (seated) EE based on mean resting EE values and variability measured in our laboratory during previous studies (Miles-Chan et al 2013;Monnard and Miles-Chan 2017).…”

“…On the day of testing, participants arrived at the laboratory at 8 h following a 12 h overnight fast. After the participant voided their bladder, body weight and height were measured using a mechanical column scale with integrated stadiometer (Seca model 709, Hamburg, Germany), and body composition determined by multifrequency bioelectrical impedance analysis (Inbody 720, Biospace Co., Ltd, Seoul, Korea), as described previously (Miles-Chan et al 2013). EE and respiratory exchange ratio (RER) were measured by breath-by-breath indirect calorimetry (Cosmed Quark, Cosmed srl, Rome, Italy) using a silicon V2 facemask (Hans Rudolph, Kansas, USA).…”

“…The participants were categorised as "energy-savers" and "energy-spenders" according to our previous definition (Miles-Chan et al 2013), namely: …”

“…"energy-savers"), and only ~20% of individuals showing a sustained increase (>5%) in energy expenditure across a 10-min standing period (i.e. "energy-spenders") (Miles-Chan et al 2013). However, the underlying metabolic and psychomotor basis of this heterogeneity is unknown.…”