22nd Mar 2024

Introduction
There is a large heterogeneity in the energy cost for posture maintenance during standing relative to sitting in healthy adults, with some showing little or no increase in energy expenditure (EE) varying between 0-5% (energy savers), while others show more substantial increases that vary between 5-25% (energy spenders). The aim of this study was to explore psychological factors that may influence such variability in human standing energetics.

Methods
EE was monitored min-by-min by indirect calorimetry in 25 healthy young adults during sitting and standing. The subjects were classified into three phenotypes on the basis of their EE during steady-state standing over 10 minutes relative to sitting, namely as savers (10% increase, n=10). These standing EE phenotypes were analysed with respect to psychological parameters, namely (i) the anxiety trait and anxiety state assessed subjectively (questionnaire) and objectively (salivary cortisol), and (ii) the desire/drive to move or to sit – assessed subjectively (questionnaire) and objectively (accelerometry) at end of study.

Results
Compared to the general healthy population, all participants were in the reference norm of the anxiety scores. The three standing EE phenotypes did not differ in anxiety trait/state, salivary cortisol nor in the rise in heart rate during steady-state standing relative to sitting. They also did not differ in desire to move or sit, nor in accelerometry parameters (no. of steps/min; vector magnitude) at end of study.

Conclusions
The differential energy cost of standing posture maintenance among the energy savers and energy spenders cannot be explained by differences in subjective or objective measures of anxiety/stress or in the desire/drive to move or sit. Whether differences in cognitive load and mental processing during standing and/or personality trait play a significant role in such heterogeneity in standing energetics remain to be investigated.