With an increase in the level of load, a decrease in metabolic volume occurs.

Employees at Hunter College at City University of New York monitored the change in the metabolic volume of marathon runners, comparing it with the volume of other athletes who participated in the studies. As a result, it was proved that with an increase in physical activity, the subjects experienced a decrease in metabolic volume. All research data was displayed in the scientific journal Science Advances.

In the USA (2013), a marathon was held, which started from Los Angeles and finished in Washington (DC). During the marathon, the athletes stopped to sleep. The duration of the marathon is 4 months. For university scientists, this marathon was a unique chance to conduct their studies on the endurance of the human body.

The main goal of the research was the metabolic volume, which is the ratio of the number of calories spent per day to the level of metabolism of the body, which is at rest. To calculate the first indicator, scientists used the method of double labeling of water molecules. Thanks to this, scientists were able to track the path of movement of isotopes of the body when measuring the volume of carbon dioxide.

For the experiment, 6 marathon runners were selected, who were examined during the first and last weeks of the marathon. According to the results of studies, it was found that with an increase in physical activity, the metabolic volume decreased.

The data from this study were compared with the data obtained during the three-month Tour de France bicycle race, which passed through Antarctica and the condition of the woman during pregnancy. The results of both studies were similar.