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

Abstract

Results Despite heterogeneity in EE response to steadystate standing, no differences were found in the amount or pattern of spontaneous weight-shifting between the two phenotypes. Whilst experimentally induced weight-shifting resulted in a mean EE increase of only 11% (range: 0-25%), intermittent leg/body displacement increased EE to >1.5 METs in all participants. Conclusions Although the variability in spontaneous weight-shifting signatures between individuals does not appear to underlie heterogeneity in the energy cost of standing posture maintenance, these studies underscore the fact that leg/body displacement, rather than standing posture alone, is needed to increase EE above the currently defined sedentary threshold. Keywords AbstractPurpose Due to sedentarity-associated disease risks, there is much interest in methods to increase low-intensity physical activity. In this context, it is widely assumed that altering posture allocation can modify energy expenditure (EE) to impact body-weight regulation and health. However, we have recently shown the existence of two distinct phenotypes pertaining to the energy cost of standing-with most individuals having no sustained increase in EE during steady-state standing relative to sitting comfortably. Here, we investigated whether these distinct phenotypes are related to the presence/absence of spontaneous "weightshifting", i.e. the redistribution of body-weight from one foot to the other. Methods Using indirect calorimetry to measure EE in young adults during sitting and 10 min of steady-state standing, we examined: (i) heterogeneity in EE during standing (n = 36); (ii) EE and spontaneous weight-shifting patterns (n = 18); (iii) EE during spontaneous weight-shifting versus experimentally induced weight-shifting (n = 7), and; (iv) EE during spontaneous weight-shifting versus intermittent leg/body displacement (n = 6).

Posture Allocation Revisited: Breaking the Sedentary Threshold of Energy Expenditure for Obesity Management

“…Whilst a certain amount of variability may be accounted for by differences in standardization and methodology, large levels of within-study variability (i.e., amongst individuals measured under identical experimental conditions) strongly suggests a large degree of true biological variability. Indeed the inter-individual variability shown in the early studies of Edholm et al (1955) and Passmore et al (1952), is almost identical to that which we have recently observed in our laboratory using contemporary equipment (Miles-Chan et al, 2013, 2017; Monnard and Miles-Chan, 2017)—i.e., ranging from individuals who showed no increase in EE during steady-state standing relative to sitting (“energy savers”) to those who showed sustained increases in EE of 25–35% (“energy spenders;” Figure 4). This is in sharp contrast to a relatively low intra-individual coefficient of variation in the energy cost of standing—reported by Miller to range from 4 to 7% (Miller, 1982), and the intra-individual coefficient of variation in EE during standing within our own laboratory to range from 0 to 7% (Miles-Chan et al, 2017).…”

“…Indeed the inter-individual variability shown in the early studies of Edholm et al (1955) and Passmore et al (1952), is almost identical to that which we have recently observed in our laboratory using contemporary equipment (Miles-Chan et al, 2013, 2017; Monnard and Miles-Chan, 2017)—i.e., ranging from individuals who showed no increase in EE during steady-state standing relative to sitting (“energy savers”) to those who showed sustained increases in EE of 25–35% (“energy spenders;” Figure 4). This is in sharp contrast to a relatively low intra-individual coefficient of variation in the energy cost of standing—reported by Miller to range from 4 to 7% (Miller, 1982), and the intra-individual coefficient of variation in EE during standing within our own laboratory to range from 0 to 7% (Miles-Chan et al, 2017). Nevertheless, using standardized experimental conditions, we have yet to observe any difference in terms of sex (Miles-Chan et al, 2013, 2017) or ethnic group (Monnard and Miles-Chan, 2017) between these two EE phenotypes.…”

“…This is in sharp contrast to a relatively low intra-individual coefficient of variation in the energy cost of standing—reported by Miller to range from 4 to 7% (Miller, 1982), and the intra-individual coefficient of variation in EE during standing within our own laboratory to range from 0 to 7% (Miles-Chan et al, 2017). Nevertheless, using standardized experimental conditions, we have yet to observe any difference in terms of sex (Miles-Chan et al, 2013, 2017) or ethnic group (Monnard and Miles-Chan, 2017) between these two EE phenotypes. Furthermore, given that during standing posture maintenance individuals appear to differ in terms of the degree and pattern of weight-shifting behavior (i.e., the redistribution of body-weight from one foot to the other), we have recently investigated if an overt difference in terms of spontaneous weight-shifting behavior could be detected between these two EE phenotypes (Miles-Chan et al, 2017).…”

“…However, there seems to be little evidence to support the notion that EE is indeed constant during standing. In fact studies conducted in our laboratory using minute-by-minute EE monitoring have shown that the majority of individuals demonstrate an initial increase in EE (most likely due to the postural transition) and then rather quickly (within 5 min) decrease their EE back to sitting values (Miles-Chan et al, 2013, 2017; Monnard and Miles-Chan, 2017; Figure 3). The rise in EE during postural transitioning is expected given the large amount of muscular contraction required to move the body weight from, for example, a sitting to standing position; but it is perhaps inclusion of this transitional period of EE, rather than consideration of only the steady-state period of posture maintenance, that has led to some of the large discrepancies in calculated energy costs.…”

“…Mean ± SEM. Left panel : measurements obtained using posture-adapted ventilated canopy indirect calorimetry (Deltatrac II, Datex-Ohmeda, Instrumentarium Corp, Helsinki, Finland) (Miles-Chan et al, 2013); Right panel : measurements obtained using facemask indirect calorimetry (Cosmed Quark, Cosmed srl, Rome, Italy) (Miles-Chan et al, 2017); Closed circles: represent “Energy-savers,” i.e., those who showed little or no change in EE (a rise in EE of <5%) during 10 min standing period relative to sitting, and also those who increased EE (a rise in EE of >5%) during first 5 min of the 10 min standing period relative to sitting but subsequently decreased EE (by >30% of the rise) during the second 5 min of this standing period; n = 18 ( left panel ) and 29 ( right panel ); Open circles: represent “Energy-spenders,” i.e., those who increased EE (a rise in EE of >5%) during first 5 min of the 10 min standing period relative to sitting, and maintained an elevated EE throughout the entire 10 min standing period (drop in EE during second 5 min <30% of the rise in EE during first 5 of standing period); n = 4 ( left panel ) and 7 ( right panel ).…”