Old School Iron Gym

About this gym

In 2008, TJ Slomka gave up a job in the delivery service industry to chase his goal of opening an all-encompassing fitness facility. What became OSI Gym started as a 5,000 sq ft space at 5139 W 140th St and grew, one room at a time, into a 60,000 sq ft facility by 2024 -- one of the largest gym facilities in America. TJ opened the space up to local graffiti artists to create a unique, engaging environment, and remains a hands-on owner, often found training clients on the floor. OSI offers over 200 machines including custom-built equipment, a 1,200 sq ft mixed martial arts mat, a 5,000 sq ft private personal-training room with turf flooring, a wrestling practice ring, and in-house recovery services (chiropractic and physical medicine, massage therapy, cold plunge, and saunas) led by Dr. Michael Diamond, D.C., CCSP. The gym also offers group classes ranging from high-intensity kickboxing to yoga, though current offerings and schedules require contacting the gym directly.

Hours