A 55-year-old Brazilian woman just did something that most elite athletes half her age wouldn’t dare attempt.
Débora Simas spent seven consecutive days running on a treadmill inside a shopping mall in Florianópolis, Brazil — and when the clock finally stopped, she had covered an extraordinary 866.21 kilometers, or roughly 538 miles.
That’s enough to beat the existing Guinness World Record by more than 12 miles.
But getting there wasn’t just a test of physical endurance — it nearly broke her entirely, and what happened on day three almost ended everything before it even got started.
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What the Seven-Day Treadmill Record Actually Involves
This isn’t your typical running record, and the rules make it brutally clear why so few attempt it.
The clock runs for exactly 168 hours — one full week — and it never stops.
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Competitors can step off the treadmill whenever they need to sleep, eat, or use the bathroom. Every single minute spent off the belt is distance permanently lost, making every rest decision a calculated sacrifice.
As previous record holder Emma Timmis put it plainly on her own website: use the seven days however you like, but the more time spent off that machine, the less ground you’ll ever cover.
Simas leaned into that reality hard. She slept in a tent set up directly behind the treadmill, ate and drank without ever stepping off the belt, and had approximately 110 support staff working around her in rotating 24-hour shifts — including doctors, physiotherapists, coaches, and official referees.
The Day Everything Almost Fell Apart
By Wednesday, August 5 — just three days in — Simas was in serious trouble.
Severe cramping hit without warning, and she came dangerously close to blacking out on the machine. Her support team was forced to rip up their entire game plan on the spot, cutting back the sleep blocks of roughly three hours she had been relying on to recover.
Her physician, Dr. Daniel de Souza Carvalho, told Brazilian outlet g1 that completing something like this demands far more than physical fitness alone.
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The near-collapse showed up in the numbers two days later — day five was her worst single-day performance, logging just 102.32 kilometers (63.6 miles).
What happened next, though, is what separates Simas from almost everyone else on the planet.
She Came Back Stronger on Day Seven
After her worst day, Simas didn’t fade. She rebuilt.
Her daily distances told a remarkable story of resilience:
- Day 1: 143.51 km (89.2 miles)
- Day 2: 126.81 km (78.8 miles)
- Day 3: 111.10 km (69.0 miles)
- Day 4: 135.58 km (84.3 miles)
- Day 5: 102.32 km (63.6 miles) — her lowest
- Day 6: 111.28 km (69.1 miles)
- Day 7: 135.61 km (84.3 miles) — her second best
She crossed the existing world record mark on Sunday morning with nearly three hours still remaining on the clock — and kept running anyway.
Her final average pace, with all sleep time factored in, worked out to 18 minutes and 44 seconds per mile across the entire week.
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Breaking Down the Record She Had to Beat
The women’s treadmill distance record has only changed hands three times in 15 years, which tells you everything about how rare this kind of performance is.
Britain’s Sharon Gayter set the original benchmark at 833.05 km back in 2011. Fellow Brit Jamie McDonald then broke the overall mark — men’s and women’s — running 843.94 km in 2019.
Then New Zealander Emma Timmis arrived in Christchurch in June 2024 and blew past both records, finishing at 846.16 km to claim the top spot outright.
Simas surpassed that by more than 20 kilometers — a gap that is anything but marginal at this level of competition.
Is It Official Yet? Not Quite
Here’s where things get complicated.
Guinness World Records doesn’t update its books the moment a runner steps off the belt. All documentation must be submitted and formally reviewed before any record is ratified — a process that can take significant time.
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As of Friday, Guinness still listed Timmis as the record holder. Simas’s team has not publicly confirmed who served as the official adjudicator during the week-long attempt, which adds another layer of uncertainty to the process.
Timmis herself understood the complexity well enough that she ran a full 48-hour trial attempt beforehand, specifically to nail down exactly what documentation Guinness would require.
There’s also a separate number floating around that complicates the picture further. A treadmill distance list maintained by recordholders.org credits Slovakia’s Michal Šuľa with 912.22 km over seven days, completed in January 2025 — but that effort has never been ratified, and the list operates entirely outside Guinness’s framework.
World Athletics also launched a formal treadmill world championship this year called Run X, complete with a $100,000 prize pool, signaling that this niche discipline is attracting serious institutional attention.
The Mindset That Carried Her Through
When Simas reflected on what those seven days actually felt like from the inside, she didn’t reach for triumph or glory.
She talked about survival.
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
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 kilometer at a time. One step at a time. For seven straight days.
Whether Guinness ultimately ratifies the record or not, what Débora Simas accomplished inside that Florianópolis shopping mall — at 55 years old, fighting through near-blackouts and relentless pain — is the kind of performance that redefines what human endurance actually looks like.
