Marathons are rigorous, demanding tests of the body’s physical capabilities, and on Sunday, 92-year-old Harriette Thompson proved age is not a factor. At the San Diego Rock ‘n’ Roll marathon, the three-time cancer survivor crossed the finish line, becoming the oldest woman to run and successfully complete a competitive 26.2-mile race.

“I was really tired at one point,” Thompson told the Charlotte Observer. “Around mile 21, I was going up a hill and it was like a mountain, and I was thinking, ‘This is sort of crazy at my age.’ But then I felt better coming down the hill.”

Charlotte, N.C., resident Thompson has 10 grandchildren and now a national marathon record. She began running at the ripe age of 76 and has since raised more than $100,000 in 16 years on behalf of the Leukemia & Lymphoma Society and Team in Training. She completed the race with a time of 7:24:36 alongside her 56-year-old son, Brenny Thompson, who serves as her bodyguard and makes sure she has the fuel she needs to complete the race safely.

Thompson surpasses 92-year-old Gladys Burrill’s record of 9:53:16 set at the 2010 Honolulu Marathon, but she doesn’t take full credit for finishing the race. Marathon training requires months of careful execution, patience, pacing, and diligence. There are only a handful of centenarians who’ve successfully completed a marathon because of the physical exertion required of the human body. However, at 90-something, when the body starts to slow, Thompson seems to be speeding up.

“[The] Leukemia & Lymphoma [Society], that’s the main reason I do run,” Thompson said. “But then I was thinking, I probably wouldn’t be here if I didn’t do this run every year, because it keeps me active all year. So I’m sort of being paid back for my efforts. People wonder how I can do it at my age, and that may be it.”