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Saturday, June 08, 2019

Ultimate limit of human endurance found

By James Gallagher for BBC News

6 June 2019

The ultimate limit of human endurance has been worked out by scientists analysing a 3,000 mile run, the Tour de France and other elite events. They showed the cap was 2.5 times the body's resting metabolic rate, or 4,000 calories a day for an average person. Anything higher than that was not sustainable in the long term. The research, by Duke University, also showed pregnant women were endurance specialists, living at nearly the limit of what the human body can cope with. The study started with the Race Across the USA in which athletes ran 3,080 miles from California to Washington DC in 140 days. Competitors were running six marathons a week for months, and scientists were investigating the effect on their bodies.

Resting metabolic rate - the calories the body burns through when it is relaxing - was recorded before and during the race. And calories burned in the extreme endurance event were recorded. The study, in Science Advances, showed energy use started off high but eventually levelled off at 2.5 times the resting metabolic rate. The study found a pattern between the length of a sporting event and energy expenditure - the longer the event, the harder it is to burn through the calories. So people can go far beyond their base metabolic rate while doing a short bout of exercise, it becomes unsustainable in the long term. The study also shows that while running a marathon may be beyond many, it is nowhere near the limit of human endurance.

Marathon (just the one) runners used 15.6 times their resting metabolic rate

Cyclists during the 23 days of the Tour de France used 4.9 times their resting metabolic rate

A 95-day Antarctic trekker used 3.5 times the resting metabolic rate

"You can do really intense stuff for a couple of days, but if you want to last longer then you have to dial it back," Dr Herman Pontzer, from Duke University, told BBC News. He added: "Every data point, for every event, is all mapped onto this beautifully crisp barrier of human endurance. Nobody we know of has ever pushed through it." During pregnancy, women's energy use peaks at 2.2 times their resting metabolic rate, the study showed.

The researchers argue the 2.5 figure may be down to the human digestive system, rather than anything to do with the heart, lungs or muscles. They found the body cannot digest, absorb and process enough calories and nutrients to sustain a higher level of energy use. The body can use up its own resources burning through fat or muscle mass - which can be recovered afterwards - in shorter events. But in extreme events - at the limits of human exhaustion - the body has to balance its energy use, the researchers argue. Dr Pontzer said the findings could eventually help athletes. "In the Tour de France, knowing where your ceiling is allows you to pace yourself smartly. Secondly, we're talking about endurance over days and weeks and months, so it is most applicable to training regimens and thinking whether they fit with the long-term metabolic limits of the body."

[I am honestly fascinated with the long distance and extreme long distance runners. What they manage to do amazes me! I don’t run much as a rule (maybe for the bus) but loved running as a child and as a teenager – it was probably because of my leg length and lung capacity. I wasn’t fast (actually one of the slowest kids in my year) but I could keep on running long after the sprinters had given up. I also loved what we used to call ‘Cross Country Running’ – off track in the open across normal rolling landscape. That was much fun…. I really must read up on these LONG races……]

7 comments:

Stephen said...

Michael Shermer, of Skeptic Magazine, founded a long-distance bike run. He says it's common for people (including himself) to be so physically taxed that they hallucinate.

VV said...

I read this today. I wasn’t surprised women in labor made the list, it’s definitely the most intense physical task I’ve ever experienced. It’s amazing what the human body is capable of. That aside, I love long distance running. I need to do more of it.

mudpuddle said...

the death valley race is the hardest one i've heard of... in california

Brian Joseph said...

Interesting stuff. I run a lot. But like you I am on the slow side. I often think of myself as the turtle in The Turtle and The Hare.

CyberKitten said...

@ Stephen: I've heard that. I've also heard about the mental state that runners (and others I guess) aim for called 'the flow' which is an almost Zen like state where you're running and not thinking......

@ V V: Yeah, the labour thing didn't surprise me at all! I'm SO glad I'm male!! Not sure if I'm taking up running any time soon but I do *walk* a lot. [grin]

@ Mudpuddle: Yes, I've heard of the Death Valley race. Crazy!

@ Brian: Slow & steady wins the race... if it's LONG enough!

Judy Krueger said...

I have a friend who runs marathons and is currently biking 10 miles a day and more on weekends for a charity event. She came to reading group Sunday evening hot and exhausted. She trains and competes regularly but is always trying to lose weight though she never does. I am not sure I understood all the calorie info but your post made me think of her. Was this a book or an article?

CyberKitten said...

@ Judy: This was an article on the BBC website. It has prompted me to look up a few books though... [grin]