A 55-year-old Brazilian ultramarathoner just did something that most people half her age couldn’t dream of completing.
Débora Simas spent seven relentless days on a treadmill inside a Florianópolis shopping mall — and walked away with what could be a new women’s world record.
She didn’t just edge past the previous mark — she obliterated it, covering an astonishing 866.21 kilometers (538.2 miles) before the clock hit 168 hours.
And here’s the thing: she still had nearly three hours left on the clock when she broke the record — but she kept going anyway.
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The Record That Never Lets You Rest
The rules of this particular challenge are as brutal as they sound.
The clock runs for exactly one week — 168 hours — and it never stops. Runners can step off to sleep, eat, or use the bathroom, but every single minute away from the belt is distance permanently surrendered.
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The previous record belonged to New Zealander Emma Timmis, who ran 846.16 km (525.77 miles) in Christchurch in June 2024. Simas, who began her attempt on August 2, surpassed that mark by a stunning 20.05 km (12.5 miles).
Her overall pace, with sleep factored in, averaged 18 minutes and 44 seconds per mile. For seven straight days.
Day by Day: A Breakdown That Defies Belief
What makes Simas’s performance even more remarkable is how she structured her week. Her daily totals weren’t a clean downward slide of a body wearing out — far from it.
- Day 1: 143.51 km (89.2 miles)
- Day 2: 126.81 km
- Day 3: 111.10 km
- Day 4: 135.58 km
- Day 5: 102.32 km (63.6 miles) — her worst day
- Day 6: 111.28 km
- Day 7: 135.61 km (84.3 miles) — her second-best day
She closed out the final day with more fire than most people start the first. That kind of mental fortitude is almost impossible to comprehend.
The Crisis That Almost Ended Everything
Day five was rough — but the real scare came two days earlier.
On Wednesday, August 5, Simas suffered severe cramping and came dangerously close to blacking out. The entire attempt hung in the balance. Her support team had to tear up their existing plan and completely restructure her sleep blocks on the fly.
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- Full-body training with one weight using swings, squats, and presses
- Solid cast iron build that feels stable and lasts for years
- Comfortable grip that makes high-rep workouts easier to handle
Her doctor, Daniel de Souza Carvalho, told Brazilian outlet g1 that completing seven days on a treadmill demands far more than physical fitness alone.
The setup around Simas was nothing short of extraordinary. She slept in a tent positioned directly behind the treadmill, ate and drank without ever stepping off the belt, and had a support army of roughly 110 people working in 24-hour rotating shifts around her — including doctors, physiotherapists, coaches, and official referees.
“My Head Had to Be Stronger Than My Body”
When it was all over, Simas reflected on the experience with a clarity that only someone who has pushed themselves to the absolute edge could articulate.
Those were seven very intense days. 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.
One step at a time. For 168 hours straight.
How the Record Has Evolved — and Why It’s Not Official Yet
This particular Guinness mark has changed hands three times in 15 years. Britain’s Sharon Gayter first set the women’s record at 833.05 km back in 2011. Fellow Brit Jamie McDonald then claimed the men’s record at 843.94 km in 2019. Timmis shattered both simultaneously when she ran 846.16 km last June.
Now Simas appears to have cleared them all — but there’s a significant catch.
If you want something simple that actually works, this is one of the most effective tools I’ve used to build strength, conditioning, and endurance without needing a full gym setup.
- Full-body training with one weight using swings, squats, and presses
- Solid cast iron build that feels stable and lasts for years
- Comfortable grip that makes high-rep workouts easier to handle
Guinness World Records doesn’t officially update the moment a runner steps off the treadmill. Evidence must be submitted and formally reviewed before any record page changes. As of Friday, Guinness still listed Timmis as the record holder, and no official statement has been made about who adjudicated Simas’s week-long run in Florianópolis.
Timmis herself ran a 48-hour trial attempt before her official record bid, specifically to learn exactly what Guinness would require from her. Simas hasn’t publicly confirmed that step has been completed.
A Bigger Number Looms — and the Sport Is Growing Fast
There’s another figure floating around the treadmill running world that complicates the picture further. A separate list maintained by recordholders.org credits Slovakia’s Michal Šuľa with 912.22 km (566.8 miles) over seven days in January 2025 — a number that dwarfs every other mark on record.
That run, however, has never been ratified, and the recordholders.org list operates independently of Guinness.
The sport itself is gaining serious mainstream momentum. World Athletics launched its first-ever treadmill world championship this year — an event called Run X — complete with a $100,000 prize pool. What was once a niche endurance curiosity is rapidly becoming something much bigger.
For Simas, though, prize money and official ratification may be secondary to what she’s already proven — that at 55, with pain, exhaustion, and near-blackout moments stacked against her, one more step is always possible.
If you want something simple that actually works, this is one of the most effective tools I’ve used to build strength, conditioning, and endurance without needing a full gym setup.
- Full-body training with one weight using swings, squats, and presses
- Solid cast iron build that feels stable and lasts for years
- Comfortable grip that makes high-rep workouts easier to handle
