“Outlander” star Caitriona Balfe isn’t just filming her hit TV series. She is also training for the London Marathon.

On Sunday, the three-time Golden Globe nominee announced she would participate in the London Marathon on April 23. She posted a video to Twitter where she is running and asks viewers, “Did somebody say the London Marathon?”

Balfe is running with her sister Anne-Marie, and they’re raising money for World Child Cancer, an organization which helps children fighting cancer in Africa, Asia and central America. “Caitriona has worked with World Child Cancer for a number of years and has seen first hand how all money gets put to great use,” the fundraising page says.

The Balfe sisters are hoping “Outlander” fans can help them raise £6,000 for the charity ahead of the London Marathon. Within two hours of posting, they already had over £2,200 raised.

Caitriona Balfe
“Outlander” star Caitriona Balfe, pictured on Jan. 7, 2018 in Beverly Hills, California, will run in the London Marathon this year. Valerie Macon/AFP/Getty Images

It should be pretty easy for them to hit their goal. According to World Child Cancer, Outlanders have helped raise over £210,000 ($293,317.50) since 2014.

The actress, who plays time-traveling nurse Claire on the Starz drama, told followers that it would be her first marathon. She also joked that she’ll start crawling if that’s what she has to do to cross the finish line.

Balfe noted that she was only beginning her training. She posted a gif of Phoebe from “Friends” to show where she’s at in her training. In a follow-up tweet, she posted a photo of co-star Sam Heughan to show where she needs to be.

Heughan, who plays Jamie Fraser on “Outlander,” is known to be quite athletic, even running a program for fans who want help while trying to get in shape. My Peak Challenge offers support, training and nutrition guides to members while also raising money for charity.

If Balfe is anything like her onscreen husband, this could be the first of many marathons. Heughan told the Los Angeles Times that it’s rather addictive.

“I wanted to challenge myself. I am slightly competitive, but it was more about myself than competing against other people,” he said in 2016. “I did my first one in Paris and loved the whole event: going to a different city, seeing all the sites, and for a space in time you feel like a professional athlete because people are cheering for you. You do one and then you want to do more.”

The two have to balance their marathons with their filming schedule. “Outlander” Season 4, which is set to debut later this year on Starz, is currently shooting.