Metabolic equivalent

The metabolic equivalent ( Engl. Metabolic equivalent of task ) - in short - is used to compare the energy consumption of a human being in various activities. It is a dimensionless quantity (not to be confused with a unit ). Moderate physical activity has about a metabolic equivalent of 3 to 6. Since the energy expenditure varies from person to person, the comparison of activities by means of metabolic equivalent is only suitable for the relative comparison of a person's energy consumption. The metabolic equivalent is used as a measure in ergometry . ${\displaystyle MET}$

definition

The metabolic equivalent is defined as the ratio of the labor turnover ( engl. Work metabolic rate ) to the resting metabolic rate ( engl. Rest metabolic rate ) defines: ${\displaystyle WMR}$ ${\displaystyle RMR}$

${\displaystyle MET={\frac {WMR}{RMR}}}$

The work rate is the metabolic rate during an activity, the resting rate is the metabolic rate during “sitting still”. Basically, there are two common definitions for the metabolic rate ( Engl. Metabolic rate ) : ${\displaystyle MR}$

• as energy turnover with the dimension of a service . The SI unit would therefore be the watt . The unit kcal / h ( kilocalories per hour ) is also used. ${\displaystyle MR_{P}}$
• as oxygen conversion with the dimension of a volume flow . The SI unit would therefore be m³ / s ( cubic meters per second ). The unit mL / min ( milliliters per minute ) is also used. ${\displaystyle MR_{\dot {V}}}$

Approximation of the resting metabolic rate

To calculate the metabolic equivalent, the resting metabolic rate is often estimated as a function of body weight : ${\displaystyle RMR}$ ${\displaystyle m}$

• as energy turnover: ${\displaystyle RMR_{P}\approx 1,0{\frac {\mathrm {kcal} }{\mathrm {h} \cdot \mathrm {kg} }}\cdot m\approx 1,163\,{\frac {\mathrm {W} }{\mathrm {kg} }}\cdot m}$
• as oxygen turnover: ${\displaystyle RMR_{\dot {V}}\approx 3,5{\frac {\mathrm {mL} }{\mathrm {min} \cdot \mathrm {kg} }}\cdot m}$

Examples

An energy consumption of 773 W (watt) is calculated for a runner (83 kg). This value is the metabolic rate and not the performance that, for example, a bicycle ergometer shows. The metabolic equivalent with the estimated resting metabolic rate is:

${\displaystyle MET\approx {\frac {773}{1,163\cdot 83}}=8,0}$

An oxygen turnover of 1800 mL / min is measured for a female boxer (62 kg). The metabolic equivalent with the estimated resting metabolic rate is:

${\displaystyle MET\approx {\frac {1800}{3,5\cdot 62}}=8,3}$

Exercise capacity

The maximum achievable metabolic equivalent is a measure of a person's physical capacity. For people or patients who have limited exercise capacity ( ), further so-called non-invasive stress tests should be carried out during operations with a medium or high cardiac risk (such as stress ECG , dobutamine stress echocardiography or adenosine myocardial scintigraphy ). ${\displaystyle MET<4}$

literature

1. ^ Austrian Federal Ministry for Social Security and Health: Sport and Health. The Effects of Sport on Health - A Socio-Economic Analysis ( Memento of September 27, 2007 in the Internet Archive ) (PDF)
2. ↑ Löllgen, Erdamm, Gitt .: Ergometry: Stress tests in clinic and practice Springer 2010, 3rd edition, ISBN 978-3-540-92729-7
3. ↑ ^{a b} Ainsworth BE, Haskell WL, Leon AS et al .: Compendium of physical activities: classification of energy costs of human physical activities. Med Sci Sports Exerc. 1993 Jan; 25 (1): 71-80. PMID 8292105
4. ^ Ainsworth BE, Haskell WL, Whitt MC et al .: Compendium of physical activities: an update of activity codes and MET intensities. Med Sci Sports Exerc. 2000 Sep; 32 (9 Suppl): S498-504. PMID 10993420
5. ↑ Poldermans, D .; Bax, JJ; Boersma, E .; et al .: Guidelines for pre-operative cardiac risk assessment and perioperative cardiac management in non-cardiac surgery: the Task Force for Preoperative Cardiac Risk Assessment and Perioperative Cardiac Management in Non-cardiac Surgery of the European Society of Cardiology (ESC) and endorsed by the European Society of Anaesthesiology (ESA). Eur Heart J 2009; 30: 2769-2812 doi : 10.1093 / eurheartj / ehp337