Woman who is nine months pregnant shocks onlookers as she runs a five-minute mile

A heavily pregnant woman has stunned onlookers at a track meet in California after blitzing her way through a five minute mile.

For those out there that live and die by kilometres, that's a near-lightning fast 3.08 minutes per kilometre.

So that, but 1.6 times over.

Move over Speedy Gonzales, because we have a new entrant on the field.

Professional middle-distance runner Makenna Myler refused to let pregnancy get in the way of her training.

She kept up her training through her first pregnancy, and now the soon-to-be mum-of-two from Orange County, California, is at it again.

The 30-year-old donned her spikes and took to the track to see if she could beat her last record while pregnant.

And she did...by eight seconds.

"I thought it was quite common to train during pregnancy but there turned out to be a lot of people who think it's not normal," she said.

"Some of it has been genetic - I know some awesome runners who got pregnant and their pelvis just couldn't take running.

"I had people asking how I could do that while nine months pregnant when they can barely get off the sofa.

"A lot of it has to do with how you fortify your body before getting pregnant - I was running before pregnancy too which helped me."

But she revealed every day is not a five minute mile day.

"There were so many days I tried to run while pregnant and it just wasn't happening, so you don't win every time. But you just keep trying," she said.

"But at the end of the day, it's important to listen to your body and only do what you're capable of, because a healthy pregnancy is the most important thing."

Myler races for Asics, competing primarily in 5km and 10km races.

Before she was pregnant, she trained a whopping six days a week to keep race ready. And that wasn't going to stop during her pregnancies, it would seem.

It all kicked off when she was pregnant with her daughter, Kenny Lou, two years ago.

Her husband, Michael, 31, started joking about how fast she could run while she was pregnant, so she set out to see what her body could do.

He joked about how fast she could run a mile while nine months pregnant and they wanted to see if she could do it in less than eight minutes.

And, boy, did she.

"It started out as a joke the first time - we thought it would be funny, but it went totally viral," she said.

"The responses weren't all positive - lots of people told me I shouldn't be exercising so hard."

But thanks to her usually rigorous training regime, her fitness level meant her body could handle more while pregnant.