The MET (Metabolic Equivalent of Task) is a physiological measure that expresses the energy cost of physical activities. It is defined as the ratio of metabolic rate during a specific physical activity to a reference metabolic rate (set by convention to 3.5 ml
The reference metabolic rate just
mentioned, is the expression of an individual’s body capacity to transport and
use oxygen during exercise and it is called VO2 (milliliters of
oxygen per kilogram of bodyweight per minute [ml/kg/min]). The maximum
reachable value of VO2 describes the maximum capacity to transport and
use oxygen during an incremental exercise and it is called VO2max.
Various methods are available to predict the VO2max value, but the
most accurate values can only be obtained with a measurement.
|Figure 1 – VO2max measurement through an ergospirometer and a treadmill.
The ergospirometer (it can be seen in Figure 1) is used to measure ventilation and oxygen and carbon dioxide concentration of the inhaled and exhaled air during a graded exercise test (in this case performed on a treadmill, but it can be done on a cycle ergometer or on a rowing ergometer, depending on the reference sport): the
VO2max is reached when oxygen consumption remains at steady state despite an increase in workload (see Figure 2).
Figure 2 – VO2 & HR vs.
speed (from rest to maximum speed).
In Figure 3 is possible to see the plateau created by the VO2 and the HR, when reaching the maximum values.
Figure 3 – VO2 & HR vs.
An average untrained man will have a VO2max of around 45 ml/kg/min, while women's values are typically 10-15% lower. These values can improve with training (altitude training is a common way, for elite athletes, to improve the VO2max values) and decrease with age, even if the degree of trainability is very variable: some individuals may double the initial values, while some others will never improve. Elite male runners can generate up to 85 ml/kg/min and female elite runners can generate up to 77 ml/kg/min, even if higher values are reported in literature.
The second part will be about the energy expenditure's splitting between fats and carbohydrates. Meanwhile...keep on training, people!
Here you can find a list of my running-related posts. Now shut down the notebook and have a run!