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October 11, 2000

Exercise Intensity and Risk of Chronic Disease

Author Affiliations

Stephen J.LurieMD, PhD, Senior EditorIndividualAuthorPhil B.FontanarosaMD, Executive Deputy EditorIndividualAuthor

JAMA. 2000;284(14):1784-1785. doi:10.1001/jama.284.14.1783

To the Editor: Dr Hu and colleagues1 found a linear inverse association between physical activity and ischemic stroke. Their study used a metabolic equivalent (MET) task measure that is derived by multiplying the self-reported intensity of physical activity by its duration. The MET measure is associated with the "volume theory," which assumes that the amount (caloric expenditure or duration) of physical activity is a critical part of the protective stimulus and that combinations of intensity and duration are relatively interchangeable.2 Therefore, with the MET measure, a person could perform an activity at a 4-MET level (intensity) for an hour and receive an MET score of 4. The same score would be obtained by performing an 8-MET activity for 30 minutes. However, these different levels of intensity may have significantly different effects.3