How the 24 Hour Fitness Founder built a gym empire

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 and 4.5 million members before selling it in 2005 for $1.6 billion. Born in Oakland, California, Mastrov identified a critical market gap—gyms weren't open 24/7—and revolutionized the fitness industry by opening up accessibility. After selling 24 Hour Fitness in 2005, Mastrov went on to gain control of Crunch Fitness and founded UFC Gym with the likes of Dana White. He even became an owner of the NBA’s Sacramento Kings. In January 2026, Mastrov teamed up with LongRange Capital to repurchase 24 Hour Fitness and continue its rejuvenation campaign post-2020 bankruptcy. Mastrov joined the Opening Bid Unfiltered podcast with Yahoo Finance executive editor Brian Sozzi to discuss the future of fitness and how to build a successful business time and again.

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