MET Values Concept

OT Dude Academy’s Free NBCOT® Exam Prep Course Cardiology MET Values Concept

  • The Metabolic Equivalent (MET) is a widely used concept that represents how energy is used for physical activities as a multiple of the resting metabolic rate (RMR).
  • It is commonly used in exercise stress testing and cardiac rehabilitation.
  • The value for one MET was originally defined as the resting level of oxygen uptake for a healthy man weighing 70 kg while sitting, or 3.5 mL O2∙kg-1∙min-1.
  • Any physical activity can therefore be viewed as a multiple of this measure.1  An average exercise level of 10 METs has been observed in nonathletic, healthy, middle-aged men.2 
  • The Compendium of Physical Activities was developed to facilitate the coding of physical activity intensity levels using a 5-digit code.
  • The Compendium of Physical Activities was developed in 1989 and published in 1993 and has been updated in 2000 and 2011.

Criticism

TLDR; MET values may not have been initially measured as accurately as we thought so researchers may change the way they measure MET values and update the MET values for activities themselves.

  • While the definition has been accepted, research indicates that the definition of MET levels may be overestimated for energy expenditure. Resting VO2 has been shown to be instead on average 2.6 ± 0.4 O2∙kg-1∙min-1, which is significantly lower than the one MET value. As the United States population is overweight or obese, these findings are very relevant.1 
  • The original definition of one MET may be population-specific, nonlinear, and does not apply to patients with chronic conditions.3 4 5 
  • Research indicates that the average MET in patients with coronary heart disease is considerably lower than the widely accepted value. Other studies have reported that the MET system underestimates the energy cost of physical activity, particularly as body fat levels increase.6 7 8 
  1. Byrne, N. M., Hills, A. P., Hunter, G. R., Weinsier, R. L., & Schutz, Y. (2005). Metabolic equivalent: one size does not fit all. Journal of Applied physiology.[↩][↩]
  2. Solak, O., Yaman, F., Ulasli, A. M., Eroglu, S., Akci, O., Ozkececi, G., … & Dundar, U. (2015). Improvement in quality of life, functional capacity, and depression level after cardiac rehabilitation. Turk J Phys Med Rehab, 61, 130-5.[↩]
  3. Milani RV, Lavie CJ, Mehra MR. Cardiopulmonary exercise testing: how do we differentiate the cause of dyspnea? Circulation. 2004;110:e27–e31.[↩]
  4. Milani R V, Lavie C J, Mehra M D, Ventura H O. Understanding the basics of cardiopulmonary exercise testing. Mayo Clin Proc. 2006;81:1603–1611.[↩]
  5. Milani RV, Lavie CJ, Spiva H. Limitations of estimating metabolic equivalents in exercise assessment in patients with coronary artery disease. Am J Cardiol. 1995;75:940–942.[↩]
  6. Howell W, Earthman C, Reid P, Delaney J, and Houtkooper L. Doubly labeled water validation of the Compendium of Physical Activities in lean and obese college women (Abstract). Med Sci Sports Exerc 31: 142, 1999.[↩]
  7. Lukaski H, Johnson P, Bolonchuk W, and Lykken G. Assessment of fat-free mass using bioelectrical impedance measurements of the human body. Am J Clin Nutr 41: 810 – 817, 1985.[↩]
  8. Swain D and Leutholtz B. Heart rate reserve is equivalent to %VO2 reserve, not to %VO2 max. Med Sci Sports Exerc 29: 410–414, 1997.[↩]
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