Metabolic Equivalent Values of Common Daily Activities in Middle-Age and Older Adults in Free-Living Environments: A Pilot Study Nicolas Aguilar-Farias, Wendy J. Brown, Tina L. Skinner, and G.M.E.E. (Geeske) Peeters Background: The purpose was to assess metabolic equivalent (MET) values of common daily activities in middle-age and older adults in free-living environments and compare these with MET values listed in the compendium of physical activities (CPA). Methods: Sixty participants (mean age = 71.5, SD = 10.8) completed a semistructured protocol of sitting, lying, self-paced walking, and 4 self-selected activities in their residences. Oxygen consumption was measured using portable indirect calorimetry, to assess METs for each activity relative to VO 2 at rest (VO 2 during activity/VO 2 at rest). Measured MET values for 20 different activities were compared with those in the CPA, for the total sample and for participants aged 55–64, 65–74, and 75–99 years. Results: Measured METs for sitting, walking, sweeping, trimming, and laundry were significantly different from the CPA values. Measured MET values for sedentary activities were lower in all age groups, and those for walking and household activities were higher in the youngest age group, than the CPA values. For gardening activities, there was a significant decline in measured METs with age. Conclusions: Some measured MET values in older people differed from those in the CPA. The values reported here may be useful for future research with younger, middle-age, and older-old people. Keywords: metabolism, measurement, physical activity assessment Most subjective and objective methods for measuring physical activity depend to some extent on the use of metabolic equivalent (MET) values. These MET values are used to account for the intensity of different activities when estimating total energy expen- diture (EE) during a period, or to classify activities according to level of intensity. For example, self-reported 24-hour recalls of all activi- ties 1 rely on MET values from the compendium of physical activities (CPAs) 2 to deduce total daily EE based on reported activities. Most commonly used surveillance questionnaires (including the Interna- tional Physical Activity Questionnaire 3 and the Active Australia Physical Activity Survey 4 ) rely on estimated MET values for groups of activities to estimate MET·minutes per week spent in moderate and vigorous physical activity. Similarly, in studies that use objec- tive methods, time spent in activities at different “intensity counts” of accelerometer data is often multiplied by corresponding MET values, if EE is the outcome of interest. The most important source of information on the MET values of activities is the CPA, 2 which was first compiled in 1993 for adults, 5 and revised in 2000 6 and 2011, 2 with a similar version for youth published in 2008. 7 However, there is no exclusive CPA for older adults, but most activities performed regularly by older adults are included in the adult CPA. In 2014, Hall et al 8 compiled data from studies in older adults and reported important differences between measured EE and estimates based on the CPA MET values. For example, for standardized tasks at a predetermined pace (eg, walking at certain speed), EE values for measured activities were about 30% higher for older adults than those in the CPA. This could be explained by an increase in the metabolic cost of physical activities with age, 9,10 due to reduced efficiency of movement, compensatory actions such as exacerbated coactivation of antagonist muscle groups, and cardiorespiratory changes. 9,11 By contrast, Hall et al 12 showed that for self-paced activities in which the individual regulates the speed or effort as desired (eg, washing dishes, vacuuming), measured EE was up to 50% lower than CPA estimates. This may be explained by the common assumption that resting VO 2 is a standard 3.5 mL·kg -1 ·min -1 , which may be 20% to 30% too high in older adults, 13 resulting in an underestimation of standard METs for specific activities in this population. 12–14 However, there are very few data on the EE of activities that are common in older people, such as household tasks and gardening, 8 and in “free- living” conditions. Accurate estimates of the MET values of such activities would enhance our understanding of the energy needs of older people. The purpose of this study was to calculate MET values for common activities performed by older adults in their own homes, based on objective measures of oxygen uptake during a range of resting, walking, household, and gardening activities. MET values were estimated for adults in 3 age groups (55–64, 65–74, and 75–99 y) and compared with those published in the CPA. Methods Participants were recruited using flyers and recruitment notices circulated through e-mail and letters within a network of volunteers and the university community. The eligibility criteria were aged 55 years and older, able to walk (with or without assistive devices but not requiring assistance from another person), able to consent, and able to perform household and/or gardening activities. Before commencing, the participants provided written informed consent. The consent form and study protocol were approved by the Aguilar-Farias is with the Department of Physical Education, Sports and Recreation, Universidad de La Frontera, Temuco, Chile. Brown and Skinner are with the School of Human Movement and Nutrition Sciences, The University of Queensland, Brisbane, QLD, Australia. Peeters is with Global Brain Health Institute, Trinity College Dublin, Dublin, Ireland. Aguilar-Farias (nicolas.aguilar@ufrontera.cl) is corresponding author. 1 Journal of Physical Activity and Health, (Ahead of Print) https://doi.org/10.1123/jpah.2016-0400 © 2018 Human Kinetics, Inc. TECHNICAL NOTE