The Upper Limit Of Human Endurance Has Been Found

Jun 14, 2019 by apost team

Are you curious about what the absolute limit is when it comes to human endurance? Well, you don’t have to simply wonder about it any longer. Scientists have been working on this question for some time, and they have recently come up with an answer.

Scientists analyzed a 3,000-mile run called Race Across the USA, the popular Tour de France, and a number of other elite sporting events. They reported in their study in Science Advances that the cap for human endurance is 2.5 times a person’s resting metabolic rate or burning 4,000 calories per day for an average individual. Anything higher than these numbers is not sustainable long term.

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The research also showed that pregnant women can endure more than previously believed.

Pregnant women are "endurance specialists" living at close to the limit of what a human body can cope with. The study cites that pregnant women are operating at 2.2 times their resting metabolic rate.

"I don't think any woman who's gone through pregnancy is surprised by this. It's pushing your body to the very limits of what you can do. The ultra ultramarathon of human endurance is pregnancy," Dr. Herman Pontzer of Duke University, a co-author of the study, told NPR, "And it plots right on that same boundary of human capability with Tour de France cyclists and Arctic trekkers and everybody else."

The scientists measured participants from The Race Across the USA for their study. In this race, men and women run 3,080 miles in 140 days. The runners start in California and end up in Washington, DC. Competitors of the race had been running six marathons every week for months before the big race. Scientists were on hand to investigate what these runs were doing to their bodies. The study also looked at the fact that while participating in a marathon is beyond the capabilities of a lot of people, it doesn’t come near how much a human can endure.

They first recorded what their resting metabolic rate was before the race. This is the number of calories a person burns while they are relaxed. The scientists then measured their metabolic rate during the race. Calories that were burned during the extreme endurance event were also recorded. The results show that while energy use starts high, it will eventually level off at about 2.5 times the person’s resting metabolic rate.

The study shows that there is a direct pattern between energy expenditure and how long a sporting event is—it is harder to burn through calories the longer the event goes on. So while an individual can surpass their base metabolic rate while exercising, he or she will not be able to sustain it in the long run and must dial it back. Dr. Pontzer confirmed:

"It's analogous to running track and field events. If you sprint for a hundred meters, you can go very fast. If you have to run a mile, it's a bit slower. If you have to run a marathon, it's even slower still," Dr. Pontzer told NPR, "And as you push yourself for longer and longer, the limits of what you're able to do go down and down. It's this sort of curved relationship between intensity and duration.

The researchers argue that this 2.5 figure might have to do with the human digestion system. They say that the human body is not able to digest and process enough nutrients and calories to stay at a high level of energy use. During extreme events, a person’s body must balance out its energy use.

Dr. Pontzer believes that their findings could help future athletes find where their “ceiling” is during events.

Watch more in the video below:

What did you think about this research? Leave a comment below and then pass this along to family and friends who are endurance athletes.