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Endurance athletes are as superhuman as possible, fueled by a seemingly inexhaustible supply of energy.
But a new study suggests that human endurance has a limit – and it's probably similar for everyone. The long-term ceiling is about 2.5 times the resting metabolic rate of the body, or 4,000 calories per day for an average person, scientists said yesterday (June 5) in the journal Science Advances.
(Resting metabolic rate is a measure of the number of calories burned by the body for basic physiological needs such as maintaining body temperature and breathing.)
To see if there was a limit to endurance, the researchers analyzed data from some of the most extreme endurance events on the planet. They measured the resting metabolic rate and calories burned by people participating in The Race Across the USA, a series of consecutive marathons that lasted several months and led California runners to Washington, D.C. [5 Running Mistakes You Didn’t Know You Make]
By analyzing the runners' urine samples from the first and last stages of the race, the researchers found that after five months of running, the athletes burned a lot less calories than at the start of the race.
They also compared the results with previously published data from other activities such as marathons, swimming, hiking in the Arctic, the Tour de France and previous years of The Race Across the USA. The researchers found that, unsurprisingly, the longer the event lasted, the more difficult it was to burn calories.
While participating in relatively short-term activities, such as a marathon, the body can sustain calories burned many times faster than the resting metabolic rate.
For example, during a marathon, runners can burn calories 15.6 times on average by their resting metabolic rate, according to the study. In the 23 days of the Tour de France, cyclists burned calories 4.9 times their resting metabolic rate and, on a 95-day trek through Antarctica, hikers burned calories 3.5 times more fast as their metabolic rate at rest.
They even examined the endurance limit of pregnant women.
The researchers also found that pregnant women operated about 2.2 times their resting metabolic rate, simply by having a baby growing up in the womb. All this to say that no matter the activity – growing a baby, crossing the United States or cycling – the body seems to have a limit to the amount of energy it can provide in the long run.
The reason for this hard term could be in the digestive system and in the amount of calories that the intestine can absorb in a day, said co-author Herman Pontzer, associate professor of anthropology of the United States. evolution at Duke University, in a statement.
Athletes do not crash when they reach this threshold of 2.5 times. They can continue, but the person can not maintain a balance between the number of calories consumed and the amount burned. Then the body begins to eat away at its own resources and the person starts to lose weight. This, in itself, is not sustainable forever.
As far as they know, no one has maintained levels above the threshold of 2.5, "so I guess it is a challenge for endurance athletes. elite, "added Pontzer. "Science works when we prove that we are wrong, maybe someone will exceed that ceiling one day and show us what we are missing."
Originally published on Science live.
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