Need to revise classification of physical activity intensity in older adults? The use of estimated METs, measured METs and V̇O2Reserve

Mathias Skjødt, Mark A Tully, Li-Tang Tsai, Kasper Degn Gejl, Niels Ørtenblad, Kurt Jensen, Annemarie Koster, Marjolein Visser, Marianne Skovsager Andersen, Paolo Caserotti

    Research output: Contribution to journalArticlepeer-review


    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 (V̇O2max). This study aimed to 1) compare classifications of activity intensity by estimated (METsestimated) and measured (METsmeasured) METs and 2) compare physical activity classified by absolute (METsmeasured) versus relative intensity (%V̇O2Reserve) in older adults.

    METHODS: Ninety-eight adults aged 75-90 years participated in the study. RMR and V̇O2 during sitting, standing, daily activities and 6-minute-walking-test were measured. V̇O2Reserve was defined as the difference between V̇O2max and RMR. Moderate and vigorous intensity was classified as 3 and 6 METs and 40% and 60% of V̇O2Reserve, respectively. Paired t-tests and a confusion matrix were used to investigate aim 1 and 2, respectively.

    RESULTS: METsmeasured was 24% lower than the standard 1 MET of 3.5 ml O2·min-1·kg-1. METsestimated underestimated the intensity during daily and walking activities when compared to METsmeasured. Nevertheless, when comparing METsmeasured to percentages of V̇O2Reserve, 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.

    CONCLUSION: Applying METsestimated for older adults leads to potential underestimation of physical activity intensity, suggesting that current classification metrics should be revised for older adults. V̇O2Reserve is a candidate metric for establishing precise physical activity intensity cut-points for older adults.

    Original languageEnglish
    JournalJournals of Gerontology, Series A
    Early online date4 May 2024
    Publication statusPublished online - 4 May 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 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


    • energy expenditure
    • resting metabolic rate
    • maximum oxygen uptake
    • aerobic reserve capacity
    • daily activities


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