Reliability of low‐power cycling efficiency in energy expenditure phenotyping of inactive men and women

• Published in: Physiological reports Vol. 5; no. 9; pp. e13233 - n/a
• Main Authors: Fares, Elie‐Jacques, Isacco, Laurie, Monnard, Cathriona R., Miles‐Chan, Jennifer L., Montani, Jean‐Pierre, Schutz, Yves, Dulloo, Abdul G.
• Format: Journal Article
• Language: English
• Published: United States John Wiley & Sons, Inc 01.05.2017; John Wiley and Sons Inc
• Subjects: Adipose Tissue and Obesity; Adolescent; Adult; Calorimetry; Efficiency; Endurance and Performance; Energy expenditure; Energy Metabolism; Exercise; Exercise Test - methods; Exercise Test - standards; Female; Habituation; Humans; Light intensity; Male; Metabolism and Regulation; obesity; Observational learning; Original Research; Oxygen Consumption; Phenotype; Phenotyping; Physical activity; Physical fitness; Physical training; Physiology; Reproducibility of Results; sedentary; Sedentary Behavior; thermogenesis; Women; Energy expenditure; thermogenesis; obesity; sedentary; physical activity
• ISSN: 2051-817X; 2051-817X
• DOI: 10.14814/phy2.13233

Standardized approaches to assess human energy expenditure (EE) are well defined at rest and at moderate to high‐intensity exercise, but not at light intensity physical activities energetically comparable with those of daily life (i.e., 1.5–4 times the resting EE, i.e., 1.5–4 METs). Our aim was to validate a graded exercise test for assessing the energy cost of low‐intensity dynamic work in physically inactive humans, that is, those who habitually do not meet the guidelines for moderate‐to‐vigorous aerobic physical activity levels. In healthy and inactive young men and women (n = 55; aged 18–32 years), EE was assessed in the overnight‐fasted state by indirect calorimetry at rest and during graded cycling between 5 and 50W for 5 min at each power output on a bicycle ergometer. Repeatability was investigated on three separate days, and the effect of cadence was investigated in the range of 40–90 rpm. Within the low power range of cycling, all subjects perceived the exercise test as “light” on the Borg scale, the preferred cadence being 60 rpm. A strong linearity of the EE‐power relationship was observed between 10 and 50 W for each individual (r > 0.98), and the calculation of delta efficiency (DE) from the regression slope indicated that DE was similar in men and women (~29%). DE showed modest inter‐individual variability with a coefficient of variation (CV) of 11%, and a low intra‐individual variability with a CV of ~ 5%. No habituation or learning effect was observed in DE across days. In conclusion, the assessment of the efficiency of low power cycling by linear regression – and conducted within the range of EE observed for low‐intensity movements of everyday life (1.5–4 METs) – extends the capacity for metabolic phenotyping in the inactive population. This work represents the validation of a methodological approach that extends the capacity for human metabolic phenotyping in the general population. It opens up new avenues for research in human energy expenditure phenotyping, with implications for the role of altered efficiency of performing low‐level dynamic work in metabolic predisposition to leanness and fatness. It could also be applied toward investigating potential changes in efficiency during the life cycle, in relation to the postulated thrifty metabolism in those exposed to developmental programming (fetal/neonatal exposure in those born small), as a component of adaptive thermogenesis in response to weight loss/gain/regain, and during potential adaptations in energy metabolism that may occur during pregnancy and lactation or during the aging process.