How the 24 Hour Fitness Founder built a gym empire

Power Players with Brian Sozzi · Mar 14, 2026 · 27m

Richard Simmons, Tony Horton, and Billy Blanks – you may know them as the larger-than-life faces of the fitness industry from the past 40 years. You know them in large part because they all came into your home through televised fitness classes and around the clock infomercials. One person from the fitness world you probably haven't heard of is Mark Mastrov, although his impact is no less than those public-facing names. Mastrov is now a 68-year-old fitness industry pioneer who co-founded 24 Hour Fitness in 1983 and transformed it from a single gym into a global powerhouse with over 420 clubs…