metabolic equivalent (MET)

metabolic equivalent (MET)

expresses the approximate energy cost (in terms of oxygen consumption) of a particular activity relative to the energy expenditure at rest, i.e. at rest MET = 1, equivalent to oxygen consumption of about 3.5 mL O2 kg-1.min-1. Scores for over 500 different activities are reported in a comprehensive and well-validated list in the Compendium of Physical Activities , e.g. walking at 3 mph: 3.3 MET; running at 8 mph: 13.3 MET. The total daily energy expenditure can be calculated, knowing body mass, the time spent in each activity and the relevant MET scores.
Table 1: Metabolic and related thresholds
TermDefinition[Lac]b mmol: L-1
Lactate threshold (LT, Tlact)Minimum work rate at which [Lac]b is found, at least in the early minutes, to be significantly above (sometimes defined as 1 mmol: L -1 above) resting value2
Anaerobic threshold (AT)
  • Work rate at which it has been considered that shortfall in oxygen supply to working muscles causes them to begin drawing on anaerobic pathways.
  • Previously taken as equating to LT but there is now good evidence that fully aerobic muscles release lactate
2
Ventilatory threshold (VT, Tvent)
  • Work rate at which the gradient of the ventilation/work rate plot increases.
  • Attributed to rise in [Lac]b so used as non-invasive indicator of LT/AT, but precision of the agreement varies with method of determining VT
2
Aerobic thresholdWork rate considered to be minimum for achievement of aerobic training effects (not that at which aerobic metabolism starts, which is of course zero)2
Maximum lactate steady state (MLSS)
  • Highest work rate which can be maintained without continuous rise in [Lac]b (see comment under OBLA).
  • Functionally equivalent to critical power ( qv ) though this is defined in terms of O2, not [Lac]b
4
Onset of blood lactate accumulation (OBLA)Work rate at which a continuous rise in [Lac]b begins. (At and a little above LT, it rises only initially, and falls gradually again after a few minutes.) OBLA is thus theoretically slightly above MLSS, but it is doubtful whether they are distinguishable in practice4