According to research conducted at Duke University in Durham, North Carolina, all endurance athletes have a metabolic limit – a maximum level of exertion that is sustainable in the long term.
Above the limit of 2.5 times a person's resting metabolic rate, the body begins to feed on itself to obtain the additional calories needed to function.
“This defines the realm of what’s possible for humans,” said study co-author Herman Pontzer, an associate professor of evolutionary anthropology, who believes the limiting factor is most likely the digestive tract’s ability to break down food.
“There’s just a limit to how many calories our guts can effectively absorb per day,” he said.
The study measured daily calories burned by a group of athletes who ran six marathons a week for five months as part of the 2015 Race Across the USA. It also looked at other feats of endurance including the Tour de France, Antarctic treks and pregnancy.
Plotted over time, the data for all events formed an L-shaped curve where athletes’ energy expenditure started out relatively high, but dropped and flattened out at 2.5 times their basal metabolic rate for the remainder of the event.
Those who ran a single marathon used 15.6 times their resting metabolic rate; Tour de France riders 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," Pontzer told BBC News.
The maximum sustainable energy expenditure found among endurance athletes was only slightly higher than the metabolic rates women sustain during pregnancy, which suggests that the same physiological limits constrain other aspects of life too, such as how big babies can grow in the womb.
Add new comment
17 comments
"OPI" going hand-in-hand with the "OTL" (left hook) and the "OTR", the latter of which was pulled on me twice yesterday
An insurance company that wants to get insurance premiums from a low risk demographic - now that's a surprise.
But it is not really about cyclists being: licensed, insured or roadworthy. It is about creating enough "reasonable" legislation to effectively remove cyclists from the road without simply calling for them to be banned which would look more unreasonable.
Indeed and then all those people who would ride to work, now jump in their cars. Then who would the cage drivers blame for the extra congestion? I saw a t shirt today, which said one car equals 9 bicycles. Imagine the chaos. Government isn't going to license cyclists, or impose registration plates, it's just tooooooo expensive to introduce and enforce. Dream on deluded drivers, including the wanker driving his mx5 who thought all cyclists were arseholes, just because I'd filtered to the front of the queue he was stuck in.
Why do these people target bikes at 0 VED as opposed to other cars that pay 0 VED? They do realise that there's cars out there paying 0 Road tax, don't they?
Pushing for cyclists to be registered is only one step away from carrying ID cards, I suppose they'd be up for this too.
Here's #1 on my wish list:
Drivers liscenses should last for 5 years and people should have to pass a refresher test to renew the liscence.
"Ben Wooltorton, CEO of InsuretheGap, said: “The explosion in bike usage in recent years is good news for the environment and should also help to ease congestion in urban areas if managed correctly.
“However, our survey picked up a definite feeling among motorists that they are often held to higher standards than their fellow road users when it comes to adherence to the Highway Code.
“Our survey also particularly highlighted that motorists are concerned about road funding, safety and also insurance, which isn’t currently compulsory for cyclists, unlike most other road users.”"
Cognitive dissonance on a society-wide scale, as a result of the msm demonising cyclists 24/7. Every single one of those statements is demonstrably wrong.
Maybe we should have a registration number on a number plate that extends five feet to the right of the bicycle, thus also indicating how much space we should have when being passed.
S-pedelecs are not ebikes in the 'cycling' sense. S stands for speed and they are limited at 45kph, not 25, as are most of the common ebikes in the UK. They must be registered, taxed and insured. So non story really - fake news? Rather like reporting a moped or motor bike rider has been caught speeding
The Volt Pulse E-bike used has a 250W motor & advertises electrical assistance to 15.5 mph or 25 kmh. So, it probably never travelled as fast with assistance as boasted, and a 25kg hybrid wouldn't be something that most people would choose to pedal fast!
I think we are posting at cross purposes - I was commenting on the "Belgian cyclist fined for speeding on S-pedelec" story.
This is proof of why democracy doesn't work; between 44% and 68% of people are morons!
Isn't the point of excise duty to penalise emissions? What emissions does a cycle have?
Indeed, the VED should be on the cyclist (in my case atleast).
Okay yes I admit it - last night I had a curry and this morning, on my way into work, I may have farted - a few times - maybe more than a few - oh and I'm maybe going to do the same in a short while when I cycle home again, but everybody farts - even car drivers and especially Audi and BMW drivers cause they are full of shit.
Isn't the Renault Twizy technically a quadricycle rather than a car?
At 18-20mph the eBike shouldn't be providing any power, given that the are limited to 15.5mph.
Correct, but you feel the main benefit when accelerating, riding into a headwind and climbing. Cruising at 18mph is fairly effortless on any bike.