24 Hour Fitness

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, 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.