Key Concepts about Physical Activity Measurement
Physical Activity Measurement
During the mid-twentieth century, epidemiological studies of physical activity and health outcomes established that higher levels of physical activity led to extended longevity and decreased risk of chronic disease. By the mid-1990s, researchers sought to quantify this inverse dose-response relationship by the volume of activity needed to reduce risk of developing a given disease.
Volume is defined by the frequency, duration, and intensity of a given physical activity. Frequency and duration are studied to understand the number of events and total length of time needed to produce health benefits, respectively. Intensity is commonly expressed as the “Metabolic Equivalent of Task” or metabolic equivalent (MET) where 1 MET equals the energy expended while sitting quietly. METs express the energy expenditure of a given activity as a multiple of the energy expenditure during rest. Therefore, a 3.0 MET activity expends 3 times the energy required to sit quietly.
When combined with duration and/or frequency, METs can be used to express physical activity volume. For example, an hour-long activity that has an intensity of 3.0 MET produces an activity volume of 3.0 MET-hours. Throughout this tutorial we discuss energy expenditure in terms of MET-hours or MET-minutes per day, week, or month.
For more information, See Ainsworth et al.1 or NHANES SP Questionnaire: Physical Activity Individual Activities Data2 for a list of activities and their associated MET values.
Ainsworth BE, Haskell WL, Herrmann SD, Meckes N, Bassett Jr DR, Tudor-Locke C, Greer JL, Vezina J, Whitt-Glover MC, Leon AS. The Compendium of Physical Activities Tracking Guide. Healthy Lifestyles Research Center, College of Nursing & Health Innovation, Arizona State University. Retrieved [May 5, 2011] from the World Wide Web.
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