Where can I work out in Marathon, Florida?
Updated: 4 days ago
You can work out in Marathon, but not the way you do at home. There’s no 24-hour chain gym here, no membership you can transfer down, no row of leg press machines waiting at mile marker 59. What you’ll find instead is a handful of small local options and a few hotels that will sell you access to theirs for the hour — including an outdoor fitness area at Grassy Flats on Grassy Key, open to guests and non-guests, $35 for the hour with the sauna and cold plunge rolled in.
If you’re driving the Overseas Highway and you just want to move your body before you get back in the car, here’s your answer.
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1. Is there a public gym in Marathon, Florida?
Yes. Marathon has two real gyms, and both will sell you a day pass without a membership.
Keys Fitness Center at mile marker 51 is the bigger of the two and calls itself the largest fitness center in the Keys. Machines, free weights, cardio, the whole conventional setup. Day passes run about $20. Doors open at six on weekdays, which matters if you’re trying to get a lift in before a charter.
Keys Strength & Conditioning at mile marker 110 is open 24 hours, which is the real draw. It’s smaller, and a few reviewers say so, but it’s the one that’s there at 4am when you’ve got a flight or a boat. They run stretch and mobility classes you can pay into without joining, and FightSports runs jiu-jitsu out of the space on Tuesday and Thursday nights.
Grassy Flats is the third option and a different thing entirely — an outdoor fitness area on the beach at Harmony Point, open to non-guests for the hour, with a wood-fired sauna and three cold plunges attached to the same pass.
If you want a bench, a rack and a mirror, go to one of the first two. The rest of this page is about the third..
2. Can I use a hotel gym in Marathon if I’m not staying there?
At most hotels in Marathon, no. The Fairfield, the Hampton Inn, the Courtyard at Faro Blanco and Hawks Cay all have fitness centers, and all of them are for people with a room key. Walking into a hotel gym you’re not staying at generally gets you a polite no at the front desk.
Two places in Marathon will actually let you in.
Isla Bella sells a resort day pass for $129, and the fitness center is included. That’s a 24-hour gym with Peloton bikes, five pools, the spa, and a mile of private beachfront. If you’re planning to spend the whole day there, that’s a fair price for what you get. If you came to lift for forty minutes, you’re paying $129 for forty minutes.
Grassy Flats sells the hour instead of the day. $35 per person gets you the outdoor fitness area at Harmony Point on Grassy Key, the wood-fired sauna, and the cold plunges. You book the hour the way you’d book a court. It’s not a walk-up, and that’s deliberate. Matt’s team wants to know you’re coming so the towels are out and the sauna is hot.
So the question isn’t which is cheaper. It’s whether you’re buying a day or an hour. Isla Bella is a day at a resort that includes a gym. Grassy Flats is a workout and a recovery session with a time on it, and then you’re back in the car or back on the water.
3. What’s in the outdoor Fitness Area at Grassy Flats?
It’s a beachside jungle gym.
Pull-up bars. Monkey bars. A dip station. A bench with kettlebells and a rack of outdoor dumbbells. A couple of air bikes and a rower. Everything built to sit outside at the western end of the property and take salt, sun and weather without falling apart.
What you won’t find is a squat rack, a leg press, a cable crossover or a mirror. That’s not a budget story. It’s a design choice, and Matt will tell you why himself.
He spent a career as a professional athlete without ever really living in a gym. It was always functional movement. Now he’s 41, two kids, plenty on his plate, and he’s found the balance between actual strength work and hitting real cardio marks. But there’s a catch he ran into: conventional lifting, done the conventional way, starts eating into his ability to move and perform on the water. You get stronger in a straight line and worse at everything the Keys are actually for.
So the tools out here are primitive on purpose. Natural body flow, natural muscle movement. Things you hang from, press off, pick up and put down.
Matt’s line for it: if you want to get jacked without hitting the gym.
It sits on Harmony Point at the westernmost tip of the property, surrounded by landscaping, with the sauna out on the beach and the cold plunges tucked in behind. Palms overhead, water on three sides, nobody’s TV bolted to the wall above a treadmill. You finish a set and you’re already looking at the flats.
4. How much does a day pass cost to work out in Marathon?
Where | Price | What You Get |
Keys Strength & Conditioning | around $20/day | Open gym, 24 hours. Weekly and monthly rates available. |
Keys Fitness Center | around $20/day | Full machine and free-weight floor. Daily, weekly, monthly and yearly rates. |
Grassy Flats | $35/person/hour | Outdoor fitness area, wood-fired sauna, cold plunges. Booked by the hour. |
Grassy Flats, expanded | $75 to $100 | The above plus watersports, paddle boards and kayaks. |
Isla Bella | $129/day | 24-hour fitness center with Pelotons, five pools, spa, private beach. |
A few things worth knowing before you pick one.
The two town gyms charge by the day. Grassy Flats charges by the hour, so the $35 isn’t a worse $20, it’s a different unit. You’re paying for a booked slot with the sauna and plunges in it, not a turnstile.
If you’re staying at Grassy Flats, Harmony Point access is already in your resort fee. You don’t pay again. Check in at the desk before you use it so they know to have towels out.
If you booked a kiteboarding day pass, that’s $50 and it includes an hour at Harmony Point. Same deal: the hour gets reserved, you don’t just wander over.
Beach club membership is the other way in, if you’re local or down often enough for that to make sense.
Call ahead at all of them. Prices in the Keys move with the season and none of these are locked.
5. Can I do a sauna and cold plunge after my workout?
Yes, and it’s the same pass. The $35 hour at Harmony Point covers the fitness area, the sauna and the plunges together. Most people use all three in one go.
Harmony Point is the westernmost tip of the property. It’s named for John Denny, a former big wave Maui surfer and one of the first people to bring paddle boards to this part of the world, who has been doing his meditation out on that point for years. The sauna sits on the beach. The plunges are tucked back behind it under shade cloths, surrounded by landscaping.
The sauna is wood-fired, holds twelve, and runs dry between 170 and 190 degrees.
There are three cold plunges, four people each, built by Emerge. They’re run at different temperatures through the day, roughly 55, 50, and down around 45 or 40, so you can pick your level or work down through them.
The thing worth knowing about the plunges is the water. These aren’t tubs full of ice. John Kleener of Live Water Sports, an old-school kiteboarding guy, builds them out of the same factory where he makes paddle boards, and he engineered a multi-stage filtration system that runs on hydrogen peroxide with no chemicals and exceeds Department of Health standards. If you’ve ever thought about what you’re getting into after the person before you sweated out a sauna and climbed in, that’s the problem this solves.
The recommended protocol: twelve minutes in the sauna, three minutes in the plunge, repeated three times. That fits inside your hour.
The rule: shower after the sauna, before the plunge. Every time. It’s not optional and it’s the reason the water stays the way it does.
You can follow the protocol or do your own thing. There are written recommendations posted, and there’s supervision out there.
6. What’s the best workout in Marathon if I’m only passing through for a day?
If you’re driving the Keys and you’ve got about ninety minutes, here’s the version that works.
Call ahead and book the hour at Harmony Point. Thirty-five dollars, and the booking matters because they cap the sauna at twelve people and they want the towels out before you get there.
The hour, roughly:
Fifteen to twenty minutes on the fitness area. Pull-ups, dips, kettlebells, a few rounds on the air bike. Enough to undo what six hours in a car does to your hips and shoulders.
Shower.
Then the contrast block: twelve minutes in the sauna, three in the plunge, repeat as the hour allows. Shower between the sauna and the plunge each time.
Rinse, change, and you’re back on the Overseas Highway.
If a conventional gym is what you actually want, both town gyms are faster and cheaper for a quick lift. Keys Strength & Conditioning is open 24 hours, which is the one that matters if you’re moving at six in the morning or ten at night. Keys Fitness Center opens at six on weekdays. Either is about twenty dollars and neither requires a booking.
Where it is: Harmony Point is at Grassy Flats on Grassy Key, north side of Marathon. Coming up from Key West it’s on your right before you hit the Seven Mile Bridge, going the other way. Coming down from Miami it’s one of the first things you reach in Marathon.
7. Where can I work out outside in the Florida Keys instead of in a gym?
The best training down here doesn’t happen in a gym. You can get your workout in all sorts of ways down in the Keys.
Matt tells a story about it. A guy went out e-foiling with Davo for an hour. Sitting on an electric foil board, going around. Fall off, climb back on, fall off, climb back on. He came in and collapsed on the beach, absolutely gassed, winded to the max. Matt asked him how it went. The guy said he thought he needed to get back in shape.
An hour on a foil board. That’s the workout.
That’s the honest answer to this question. At Grassy Flats most of the real fitness lives inside the watersports, not next to them.
The aqua park. RumRunner is the largest inflatable park in the Keys. You will climb, fall, swim and climb again for an hour straight. Matt’s framing: if you’re going to sit on the beach all day, you want to feel like you earned it a little.
The cable park. Keys Cable is the only one in the Florida Keys. Two towers, nearly 700 feet of cable, instruction included. Riding a cable is a grip and core workout disguised as fun, and you’ll know it the next morning.
Paddling. The Live boards are catamaran-style and stable enough for yoga. The outrigger canoe and sandbar sail run about two hours, and you’re paddling with your own muscles against the wind the whole way. Areta’s line is that it’s the best way to actually get on the water.
Kiteboarding, wing foiling, e-foiling. The progression programs are built as programs, beginner through advanced, and they’re physical work from the first session.
None of this gets called a fitness class, and there’s no schedule of classes to sign up for. Matt’s been clear about that. The courses are the water.
Which is the point. You can spend an hour under fluorescent lights looking at a mirror, or you can spend an hour falling off a foil board in four feet of warm water and arrive at roughly the same place, except one of them you’ll want to do again tomorrow.
8. Are there fitness classes or personal trainers in Marathon?
At Grassy Flats, not yet. There’s no class schedule at the fitness area and no trainer on staff. You book the hour and you run your own session. Matt has relationships with personal trainers around the community he wants to bring out and make available, but that’s a plan, not something you can book today.
The one exception is the retreats. A few times a year Matt runs guided sessions at Harmony Point with breath work built into the sauna and plunge cycle. Those are scheduled, not on demand. Ask what’s on the calendar when you book.
In town, there’s more. Keys Strength & Conditioning runs stretch and mobility classes several times a day, early morning through late afternoon, and you don’t need a membership. You pay the daily fee and walk in. They also host jiu-jitsu through FightSports Florida Keys on Tuesday and Thursday nights, kids first, adults after.
What Marathon doesn’t have, and it’s worth knowing before you book a trip around it: there’s no sports medicine practice down here that Matt would send you to. He’s been asked and he says it straight. If you’re coming off an injury or you need bodywork mid-trip, sort that out before you drive down. There’s a massage therapist Grassy Flats can call and someone for facials, but there’s no spa on property and no one on site.
9. Is the Fitness Area at Grassy Flats air conditioned?
No. All of it is outside. The fitness area, the sauna, the plunges, all of it sits on Harmony Point in the open air, shade cloths over the plunges and landscaping around the rest.
That’s the appeal for most people and a dealbreaker for some.
It matters most in July and August, midday. Heat and sun will end the session before your workout does, and there’s no air conditioning to retreat into. Early morning and late afternoon are the hours that work. If you train in climate control and that’s non-negotiable, the town gyms are the answer and there’s no hard feelings in it.
10. How do I book a workout day pass at Grassy Flats?
Call ahead. The hour has to be reserved, so this isn’t a walk-up.
What you’re booking: one hour at Harmony Point, $35 per person. That covers the outdoor fitness area, the wood-fired sauna and the three cold plunges.
Why the booking matters: the sauna caps at twelve people and the plunges hold four each. Reserving the hour is how they keep it from being a scrum, and it’s how the towels are out and the sauna is hot when you get there.
What to bring: swimsuit, and that’s about it. Towels are provided.
If you’re staying at Grassy Flats, it’s already in your resort fee. Check in at the front desk before you head out so they know you’re coming.
If you booked a kiteboarding day pass, that’s $50 and it includes an hour at Harmony Point. Same thing, book the hour.
If you’re down here often, ask about the beach club membership instead of paying per visit.
Where: Grassy Flats Resort & Beach Club on Grassy Key, north end of Marathon. Harmony Point is the westernmost tip of the property.
On your way out, the Land & Sea Market is on site. Protein bowls, quinoa bowls, cold-pressed shots in the cold case. Nothing on those shelves has an ingredient you can’t pronounce, which after an hour of this is sort of the point.
11. FAQ
Does Marathon have a 24-hour gym?
Yes. Keys Fitness Center at 5101 Overseas Highway and Keys Strength & Conditioning at 10994 Overseas Highway both sell day passes without a membership. Keys Strength & Conditioning is open 24 hours. Grassy Flats on Grassy Key also sells hourly access to an outdoor fitness area with a sauna and cold plunges.
Is the Fitness Area included in the resort fee at Grassy Flats?
Yes. Harmony Point access is included for hotel guests. Check in at the front desk before using it.
Can non-guests use the Grassy Flats Fitness Area?
Yes. $35 per person covers an hour at Harmony Point, including the outdoor fitness area, the wood-fired sauna and the cold plunges. You don’t need to be staying at the resort. The hour has to be booked in advance.
Is the Fitness Area indoors or outdoors?
Outdoors. The fitness area, sauna and cold plunges are all outdoors at Harmony Point, the westernmost tip of the property.
Do I need to book ahead?
Yes. The sauna holds twelve people and each cold plunge holds four, so access runs on booked hourly slots rather than walk-ups.
Can I get a massage or see a physio in Marathon?
Grassy Flats can call a massage therapist and has someone for facials, but there is no spa on property and no practitioner on site. Marathon has no sports medicine practice the Grassy Flats team currently recommends.
