24 Hour Fitness
US fitness center chain
24 Hour Fitness is a privately held and operated fitness center chain headquartered in Carlsbad, California. It is the second largest fitness chain in the United States based on revenue after LA Fitness, and the fourth in number of clubs (behind LA Fitness, Anytime Fitness, and Gold's Gym), operating 244 clubs across nine U.S. states. The company was originally founded by Mark S. Mastrov and was sold to Forstmann Little & Co in 2005, and then to AEA investors and Ontario Teachers Pension Plan in 2014.
After the COVID-19 pandemic forced gym closures and ravaged the fitness industry in 2020, the company filed for bankruptcy in June 2020, closed over 130 clubs, and successfully emerged from bankruptcy under new owners Sculptor Capital Investments LLC, Monarch Alternative Capital LP and Cyrus Capital Partners LP in December, 2020.
History
Early history and founding
24 Hour Fitness was founded initially as 24 Hour Nautilus in 1983, in San Leandro, CA by Mark Mastrov. With the merger of the #2 and #3 largest fitness chains in the United States. Mastrov had been using a local gym for rehab after a knee injury, and turned the gym into a 24-hour Nautilus facility after buying out the owner. The company was originally named "24 Hour Nautilus", but in 1996 it merged with Carlsbad, California-based company "Family Fitness" (founded by Ray Wilson in 1977) which resulted in both brands emerging as "24 Hour Fitness"
2004–2008: Olympics and other sponsorships
In 2004, 24 Hour Fitness became a sponsor of the 2004–2008 United States Olympic teams. The sponsorship grants memberships to some U.S. Olympic hopefuls, and includes upgrades to some U.S. Olympic Training Centers across the country, including renovation of the facility in Colorado Springs, Colorado, in 2004 to be followed by Lake Placid, New York, and Chula Vista, California.
24 Hour Fitness partnered with NBC to develop a reality show, The Biggest Loser, which features 12 to 22 overweight contestants competing to lose weight over several million dollars.
“24 Hour Fitness” enters the record as uS fitness center chain. Crown Archives preserves that source wording while asking what Hour, Fitness and fitness can confirm, complicate or overturn.
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The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Sep 13, 2026. The linked authority identifier is Q4631849. 2 of 2 selected statements include explicit references; 1 carry qualifiers and 0 use preferred rank. The first chronological checks are 2005, 2014, 2020 and 1983.
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This entry incorporates text from “24 Hour Fitness” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.