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Am J Cardiol. 2018 Feb 1;121(3):382-387. doi: 10.1016/j.amjcard.2017.10.033. Epub 2017 Oct 31.

Using Metabolic Equivalents in Clinical Practice.

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Preventive Cardiology and Cardiac Rehabilitation, William Beaumont Hospital, Royal Oak, Michigan; Oakland University William Beaumont School of Medicine, Rochester, Michigan. Electronic address:
Cardiovascular Medicine, William Beaumont Hospital, Royal Oak, Michigan.
Cardiovascular Medicine and Coronary Interventions, Stanford Prevention Research Center, Stanford University School of Medicine (Emeritus), Redwood City, California.
Department of Cardiovascular Diseases, John Ochsner Heart and Vascular Institute, Ochsner Clinical School-The University of Queensland School of Medicine, New Orleans, Louisiana.
INTERVENT International, Savannah, Georgia.
Emory Heart Disease Prevention Center, Emory University School of Medicine, Atlanta, Georgia.


Metabolic equivalents, or METs, are routinely employed as a guide to exercise training and activity prescription and to categorize cardiorespiratory fitness (CRF). There are, however, inherent limitations to the concept, as well as common misapplications. CRF and the patient's capacity for physical activity are often overestimated and underestimated, respectively. Moreover, frequently cited fitness thresholds associated with the highest and lowest mortality rates may be misleading, as these are influenced by several factors, including age and gender. The conventional assumption that 1 MET = 3.5 mL O2/kg/min has been challenged in numerous studies that indicate a significant overestimation of actual resting energy expenditure in some populations, including coronary patients, the morbidly obese, and individuals taking β-blockers. These data have implications for classifying relative energy expenditure at submaximal and peak exercise. Heart rate may be used to approximate activity METs, resulting in a promising new fitness metric termed the "personal activity intelligence" or PAI score. Despite some limitations, the MET concept provides a useful method to quantitate CRF and define a repertoire of physical activities that are likely to be safe and therapeutic. In conclusion, for previously inactive adults, moderate-to-vigorous physical activity, which corresponds to ≥3 METs, may increase MET capacity and decrease the risk of future cardiac events.

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