Need to Revise Classification of Physical Activity Intensity in Older Adults? The Use of Estimated METs, Measured METs, and V̇O2 Reserve
In: The journals of gerontology. Series A, Biological sciences, medical sciences, Band 79, Heft 8
ISSN: 1758-535X
Abstract
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 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 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.
Clinical Trials Registration Number: NCT04821713