The Mecca
Origins of OSI
In 2008, TJ Slomka gave up a successful job in the delivery service industry to chase his goal of opening an all-encompassing fitness facility.
That’s how OSI Gym was born. One room at a time, he took over 5139 W 140th — growing it from 5,000 sq ft in 2008 to 42,000 sq ft in 2024. He opened the walls to local graffiti artists, creating an environment you won’t find anywhere else.
TJ is not an absent owner — you’ll find him around the gym checking in or training clients. As an athlete born and raised west of Cleveland, his mission is to give back to the community that made him by sharing his expertise and his facility.
He makes sure the trainers, staff and equipment are of the highest caliber, and he keeps upgrading the gym with quality and member feedback in mind.
- 2008
- OSI opens with 5,000 sq ft
- 2024
- Grown to 42,000 sq ft
For every level
We achieve greatness together
Whether you’re just starting your fitness journey, returning to the gym, or ready to take your training to the next level, Old School Iron has everything you need. Our expert trainers will help you reach your goals — from weight loss to bodybuilding, triathlon prep or building mental stamina.
As you progress, the facility gives you a motivating environment full of adrenaline, friendly competition and no limits. Advanced athletes can push even further with over 200 machines, plus recovery services like physical therapy and chiropractic care.
In their words
Members speak
“I started to come here because I started taking the gym really serious and it became a safe haven for me… You have really amazing people here that really give you the feeling that you are welcomed… You would think people here are intimidating, but it is really the polar opposite.”
Max Hess · Member
“It’s a very hard-core working atmosphere. You see people working, you see people pushing, you see people are serious. TJ spares no expense on equipment… all kinds of equipment here you don’t see at other gyms. He’s a great gym owner to work with and provides one of the best atmospheres for training. There is no gym I would rather train at.”
Big Mike Ely · Pro bodybuilder