Background: Multiples of resting metabolic rate (RMR) are often used to classify physical activity intensity, a concept known as the metabolic equivalent of task (MET). However, the METs metrics may misclassify physical activity intensity in older adults because of age-related changes in RMR and maximal aerobic capacity (V O2max). This study aimed to (i) compare classifications of activity intensity by estimated (METsestimated) and measured (METsmeasured) METs and (ii) compare physical activity classified by absolute (METsmeasured) versus relative intensity (%V O2Reserve) in older adults. Methods: Ninety-eight adults aged 75-90 years participated in the study. RMR and V O2 during sitting, standing, daily activities, and 6-minute walking test were measured. V O2Reserve was defined as the difference between V O2max and RMR. Moderate and vigorous intensity was classified as 3 and 6 METs and 40% and 60% of V O2Reserve, respectively. Paired t tests and a confusion matrix were used to investigate aims 1 and 2, respectively. Results: METsmeasured was 24% lower than the standard 1 MET of 3.5 mL O2min-1·kg-1. METsestimated underestimated the intensity during daily and walking activities when compared to METsmeasured. Nevertheless, when comparing METsmeasured to percentages of V O2Reserve, a mismatch was shown for moderate intensity in 47%-67% of the participants during daily activities and 21% of the participants during self-selected gait speed. Conclusions: Applying METsestimated for older adults leads to potential underestimation of physical activity intensity, suggesting that current classification metrics should be revised for older adults. V O2Reserve is a candidate metric for establishing precise physical activity intensity cut points for older adults.

Original languageEnglish
Article numberglae120
JournalThe journals of gerontology. Series A, Biological sciences and medical sciences
Issue number7
Publication statusPublished - 1. Jul 2024

Bibliographical note

© The Author(s) 2024. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For commercial re-use, please contact [email protected] for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact [email protected].


  • Aerobic reserve capacity
  • Daily activities
  • Energy expenditure
  • Maximum oxygen uptake
  • Resting metabolic rate
  • Basal Metabolism/physiology
  • Humans
  • Exercise/physiology
  • Male
  • Activities of Daily Living
  • Oxygen Consumption/physiology
  • Aged, 80 and over
  • Female
  • Aged
  • Metabolic Equivalent


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