Brazilian Runner, 55, Breaks Women’s Treadmill World Record With 866 Kilometers

Débora Simas still had two hours and 46 minutes to run when she passed the world record on Sunday morning. She kept going anyway, and when the clock reached 168 hours at noon, the 55-year-old Brazilian ultramarathoner had covered 866.21 kilometers (538.2 miles) on a treadmill in a Florianópolis shopping mall.

The record works like this. The clock runs for one week and never stops. A runner can step off whenever he or she wants, to eat, sleep, or use the bathroom, and every minute off the belt is distance they do not get back. Emma Timmis, who held the mark until Sunday, described it on her own site: use the seven days however you like, and the more of them you spend off the treadmill, the less ground you cover.

Timmis, a New Zealander, ran 846.16 km (525.77 miles) in Christchurch in June 2024. Simas, who started on Aug. 2, beat it by 20.05 km (12.5 miles), averaging 18:44 per mile with sleep included.

Her daily totals did not simply decline. She ran 143.51 km (89.2 miles) on the first day and 102.32 km (63.6 miles) on the fifth, her worst, then closed with 135.61 km (84.3 miles) on the seventh, her second best. The four other days went 126.81, 111.10, 135.58 and 111.28 km.

That fifth day came two days after the attempt nearly ended. Simas cramped badly on Wednesday, Aug. 5, and came close to blacking out. Her team rewrote the plan and cut into the sleep blocks of around three hours she had been taking. Seven days of running takes more than fitness, her doctor, Daniel de Souza Carvalho, told g1, the Globo site that covered the week most fully. She slept in a tent behind the machine, ate and drank without stepping off, and had about 110 people working around her in 24-hour shifts, among them doctors, physiotherapists, coaches and referees.

The mark has moved three times in 15 years, and the last move was a big one. Sharon Gayter of Britain set the women’s record at 833.05 km in 2011. Jamie McDonald, also British, ran 843.94 km in 2019 to take the men’s. Then Timmis passed Gayter last June and kept running until she had passed McDonald too.

A Guinness record is not official the moment a runner steps off. The evidence goes to the organization and is reviewed before the page changes, which is why Timmis ran a 48-hour trial attempt beforehand to find out exactly what Guinness would want from her, parkrun New Zealand reported. Simas has not cleared that step. Guinness still listed Timmis on Friday, and nobody in Florianópolis has said publicly who adjudicated the week.

A bigger number is in circulation. A treadmill list kept by recordholders.org has Michal Šuľa of Slovakia at 912.22 km (566.8 miles) over seven days in January 2025. That list is not Guinness, and the run has never been ratified. World Athletics launched a treadmill world championship this year, run X, with a $100,000 prize pool.

“Those were seven very intense days,” Simas told g1, in remarks translated from Portuguese. “I had to face the sleepiness, the pain, the exhaustion and moments when my head had to be stronger than my body. … So I tried not to think about the more than 846 kilometers. I thought about the next kilometer, the next step.”