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We already knew that pregnant women were tough, but we had no idea just how tough..
It'll come as no surprise that growing another human inside of you takes its toll on the female body. Weight gain, backaches, joint pain, incontinence, and skin stretching are part and parcel of pregnancy - and this is all before we get to the actual labour.
A new study has identified the ultimate limit of human endurance, by analysing runners who run 3,000 mile runs and other elite events such as Tour de France.
The study by Duke University found that the cap of physical endurance was 2.5 times the body's resting metabolic rate. This equates to 4,000 calories burnt a day for an average person.
During pregnancy, women's energy use peaks at 2.2 times their resting metabolic rate - so not far off the limit at all.
We knew the female body was amazing but wow.
The study, published in Science Advances, analysed runners competing in the Race Across the USA which ran 3,080 miles from California to Washington DC in 140 days.
Scientists investigated the effect six marathons per week were having on their bodies. They tested their metabolic rate before and after the run.
The study found that the longer the event, the harder it is to burn as much calories. Essentially, people can push their metabolic rate for short periods of time but it becomes unsustainable in the long term.
"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."
So there you have it: for anyone that doubted how physically draining an punishing pregnancy can be, it's been proved the pregnant body is working at nearly the same endurance as marathon runners.
Pretty badass if you ask us.
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