Study: The limit of human endurance is determined by food, not temperature.

Scientists say human endurance is limited and depends on the intestines, not the brain or muscles, according to British media.
Researchers in the UNITED States and Scotland looked at people who ran six marathons a week to the highest physical requirements for pregnancy, and found that the amount of calories a day the body can absorb determines the upper limit of a person's performance, The Independent reported on June 5.
, the threshold is equivalent to 2.5 times the amount of energy they consume when they rest, and beyond that, the body begins to break down fat, muscle and connective tissue to make up for the calorie deficiency, the Report said.
, an evolutionary anthropologist at Duke University in North Carolina and one of the study's authors, said: "This defines what humans can do. There is a limit to the number of calories our gut can effectively absorb each day. The
team collected the latest energy consumption data from the five-month "Crossing America" marathon, which lasted 3,080 miles. The researchers found that athletes' energy consumption started high and then plummeted to the 2.5-fold limit.
researchers used urine samples to measure calorie consumption, once when the race started in California and again after a 20-week marathon near Washington.
found that the contestants burned 600 fewer calories a day than predicted at the starting rhythm.
that if they kept their energy-spending speed, the contestants would be able to complete no more than half of the race.
Although this is the longest distance race to assess metabolic data, researchers surveyed summer Tour de France runners, 100-mile marathon runners and explorers crossing Antarctica and found that their energy expenditures were similarly capped at 2.5 times the benchmark rate.
said temperature did not appear to have a significant effect, which the researchers said was "unexpected" because previous theories suggested that the body's maximum energy consumption was determined by heat dissipation.
study also found that the amount of calories burned in pregnant women was close to the 2.5-fold energy consumption limit for endurance athletes, suggesting that endurance thresholds were independent of the muscles or organs involved,
reported.Writing in the journal Science Advances, the authors of the report said:
Humans have evolved more endurance than other apes, often due to natural selection, in order to adapt to more and more physical activity, especially long-distance running. But
raising this endurance threshold may also have other benefits, such as prolonging pregnancy or having a brain that is larger - and more energy-consuming - than our primate ancestors. He Jinxuan.