Study Finds That Being Pregnant Is Like Constantly Running A Marathon

Scientists studying the ultimate limit of human endurance found that being pregnant is akin to constantly running a marathon

Maybe it should be called the Ironwoman.

A new study on the limits of human endurance, conducted by Duke University, has found that one of the most extreme experiences that a person can endure isn’t an Ironman race or an ultra marathon. It’s pregnancy.

The study, which was published in Science Advances this month, took an in-depth look at what happens to the bodies of elite athletes participating in the most challenging races in the world, including the Ironman, the Tour de France, and the 3,000-mile Race Across the U.S.A., in which competitors ran six marathons a week over 120 days. But they found that one of the very hardest things you can do is carry a baby to term over nine months.

Some people (cough cough men) seem surprised to hear this, while others (hi, mom!) are like, how much money did you spend to figure this out?

The study centered on the resting metabolic rate (also known as the basal metabolic rate) of certain activities and found that the human body can’t endure more than 2.5 times this rate without eventually breaking down and dying. At that point, your tissue and muscle begins to break down, and your digestive system is compromised.

“Every mother who has gone through a pregnancy has experienced that effort themselves,” said study co-author and evolutionary anthropology professor Herman Pontzer. “Pregnancy is the longest duration, highest energy expenditure thing that humans can do. Mothers probably aren’t surprised by this.”

No we aren’t, said every mother everywhere.

Researchers think that moms are pushed to the limit because of the nature of our pregnancies — and that we would literally not be able to continue being pregnant after nine months because of the strain it put on our physical bodies. In fact, these limits are probably why we can only carry babies for a certain timeframe and to a certain size.

“Human mothers have the biggest children and the longest pregnancies of all apes,” Pontzer said.

While events like marathons can raise your basal metabolic rate to much higher than 2.5, it can’t stay there for long without causing health problems, and without your body calling for rest. The amazing thing about pregnancy is that moms never get a rest — they are performing at an elevated level 24 hours a day, seven days a week, until the baby is born (and really, do we rest at that point?).

“All of the limits of our endurance, whether we’re talking about cycling or running or trekking across to the South Pole or, you know, building a kid — all of those really high effort endeavors are all governed and all constrained by the same machinery,” Pontzer said.

So yes: next time anyone doesn’t seem to understand why you are tired during your pregnancy, or that you need to buy a special pillow, or that you need an extra nap, or that you absolutely need french fries, please explain to them that making a baby is basically like trekking to the South Pole on foot or running from California to Washington, DC, and that they can eat it.

Also: this is even more evidence that we should not, in any way, ever force a woman to remain pregnant when she and her doctor think otherwise.