Ultra-runner Stephanie Case has made history by becoming the first woman to complete an extreme 100-mile race in Antarctica.

The Antarctic Ice Ultra consists of 38 loops of a 4.2km course in the Schirmacher Oasis in Queen Maud Land, East Antarctica.

The 43-year-old ran alongside penguins and battled severe wind and temperatures as low as -35C - the coldest organisers have ever seen - to cross the finish line in second place overall in a time of 17 hours 31 minutes and 39 seconds.

Due to the harsh weather conditions, the race was brought forward to start at 1am on Sunday morning and Case says it was as much about survival as performance.

"When you're out in that environment for 20 minutes it's OK but when you're out in it for 17 hours or more, it can take a huge toll on the body because you have to expend so much energy just to keep yourself warm," Case told BBC Sport.

"The thing is that you need to run fast, but you need to do it in a way that you don't sweat, because if you sweat, that's a killer. It will make you cold instantly."

'Going to the bathroom was a real challenge'

Such is the brutal nature of the challenge on a continent that has 24/7 daylight, very few people attempt it each year and even fewer finish. This year, only four of the eight runners that started the 100-mile race crossed the finish line.

Previously only ever attempted by men, Case was one of three women on the start line but the Canadian was the only one to finish.

One of the challenges Case had not considered though, as a self-declared "mountain goat", was managing toilet breaks in the extreme temperatures.

"On a trail you could normally just go in the woods, but due to bio-security reasons, you can't leave any trace in Antarctica. And then going to the bathroom, when you are wearing so many layers and taking off your gloves for even five seconds can put your hands at risk of frostbite, it was a real challenge," she said.

"The environment is so harsh, and things can go wrong so quickly… It was just relief when I crossed the finish line that I'd actually done it and in a time that I was super proud of. It was just an outpouring of emotion."

The human rights lawyer crossed the line 29 minutes after Chinese runner Yusheng Ni, who smashed his own world record - set last year - by over five and a half hours.

Alongside making history, Case had also been chasing the world record but knew she would have a "formidable challenge" on her hands with Ni, who has completed more than 500 ultramarathons, in the pack.

"There were parts where I was 60 seconds behind him or I was sometimes just 200 metres behind him. It was a real race. But whenever he saw me getting close, he would look behind and he would just take off. I think we really pushed each other to get our best performances. I feel super proud of what I was able to do," she said.

Case went viral last year for breastfeeding her baby daughter Pepper during her victory at an ultramarathon in Snowdownia.

While the response was largely positive, she says some of the backlash she received is what inspired her to take on this challenge to show "motherhood is not the finish line". To do it in a place that has historically been described as the "womanless continent", she says, is a fitting achievement.

"I know that when I'm going out and doing the things that make me feel happy and whole, it makes me a better mum and I can come home and and show my daughter all the things that she might want to do and all the things that are possible for women," Case said.

"I felt like the best way to clap back at anyone who thought that I should be at home with my baby was to go to the most extreme place on Earth and try to get the record."