Two and a half times the limits of what is possible for people
The papers published in Science Advances are a clear judgment. Whatever the performance challenge, the athlete ultimately determines the metabolic limit. The maximum amount of energy that a person can endure in the long run. Where the limits lie, scientists have been trying to find out for years.
“People have tried to find a single indication, namely the level of energy consumption, which is sustainable to infinity. They’ve seen extreme races like the Tour de France to find that number, “explains fellow student Herman Pontzer, an evolutionary anthropologist at Duke University
Pontzer and his team have both their own words and the statements of his colleagues enforced. They pretty much set the limit. They found that in the long run, people can only burn calories by up to two and a half times their metabolism, that is, the energy release caused by normal body surgery. Breathing, maintaining blood circulation and body temperature. More of that does not express the body except at the expense of its own destruction.
“Two and a half times the limits of what is possible for people,” says Pontzer. From two and a half times energy consumption, the body begins to replace its own tissue with desperate efforts to balance out the calorie deficit.
At the same time, the researchers add that they do not disturb their borders by eating more and replace the increased energy expenditure with a “kicked” income. Our digestive tract knows the limits. He is able to eat, absorb and process only a certain amount of food. “There is a limit to how many calories our body can absorb daily,” says Pontzer. The limit is only two and a half times the normal calorie intake.
Harvard University evolutionary biologist Daniel Lieberman, who was interviewed by the ScienceMag server, said the study was convincing and authoritative. “That’s impressive data. The finding that extreme human endurance has a hard line is very compelling, “said Lieberman.
Do magic two and a half times.
In 2015, the researchers seized six runners who participated in the Extreme Race Across race in the United States. Twenty weeks later, in a long marathon, the athletes have to cover a total of 4,957 kilometers – from Los Angeles to Washington.
To find out how many calories they burn, they replace hydrogen and oxygen in drinking water with the harmless isotopes of these elements. By chemically monitoring how these isotopes secrete the body of athletes in urine, sweat and exhaled air, they can calculate how many athletes produce carbon dioxide. This measurement is directly related to the number of calories burned.
“The changes in energy costs for athletes have been overwhelming,” says the New York Times. In the first week of repeated marathons, runners burned an average of 6,200 calories a day. This was a significant advance over the typical pre-race performance.
Twenty weeks later, however, the measurements yielded completely different data. Athletes consume an average of 600 calories less. And that despite the same distance at the same speed. Due to the lower power consumption, nothing is lost.
Scientists have calculated that at the beginning of the race, the athlete’s metabolism tripled compared to rest time, while the last 20 weeks of racing were two and a half times higher.
In order to find out not only the sample and the type of extreme stress, scientists compared the results with the metabolic data of former athletes who have completed triathlons, ultramarathons, long cycling races like the Tour de France and Arctic expeditions.
The authors of the study found that after 12 hours of strenuous physical activity, participants’ energy expenditure increased significantly. Finally, he decided, however, for the two and a half times normal resting metabolism.
Crucial to this two-and-a-half-year result were early, really special investigations that amazed the volunteers. This allowed the scientists to observe how much and how fast they would win. The measurements showed that the subjects had at most two and a half times their basic calorie requirement. This means that although they could get more calories, their bodies could not handle anything beyond that limit.
According to Pontzer, this could mean that our organism somehow recognizes the danger of crossing a line beyond which we can not replace the energy emitted. And since more than two and a half times the normal calorie consumption is not able to handle our body, in the long run we can not lose more than two and a half times the noiseless energy consumption, explains Pontzer.
It does not hide the fact that there are no answers from his colleagues about how our body will hold this line. It is believed that the body can save energy by limiting physiological processes such as the immune response.
For top athletes, learning means a stop sign that prevents them from riding longer and faster. Just because more calories do not work.
Pregnancy as endurance discipline
In addition, the researchers found that the energy costs of pregnant women are almost two and a half times higher. “Pregnancy is the biggest time-consuming energy expenditure that people can cause,” says Pontzer, summing up the New York Post.
According to researchers, pregnant women work about 2.2 times their remaining sales in 270 days. “If the value went up, pregnancy would be intolerable, damage the body, and could be fatal,” the book says.
Pontzer sees the relationship between seemingly different activities such as pregnancy and, for example, extreme ultra-marathons as a “fun evolutionary connection” that science has never known before. He also points to the hypothesis that evolution has put man in the state in which he was built.
“Humans are really stubborn primates,” Pontzer told The Scientist, saying that their long-term skills are much better than those of other primates. And because pregnancy and strenuous physical activity are caused by the same biological mechanism, Pontzer suggests that people who are able to cope with perseverance through evolution also have the opportunity to “have larger children and have them more often.” is a secondary consequence of the ability to handle larger children with older children.