The Founder of 24 Hour Fitness Worldwide Inc., the world's largest health and fitness company serving more than 3.5 million members in the United States and Asia, Mastrov borrowed $15,000 to open his first fitness center in California in 1983. After a dramatic expansion, he sold 24 Hour Fitness in May 2005 for $1.65 billion.

Within the health and fitness industry, Mastrov is considered an innovator and visionary, not only for introducing such club services as around-the-clock access, month-to-month memberships and electronic fund transfers, but also for sponsoring the U.S. Olympic team, partnering with celebrities to open co-branded clubs and supporting NBC's reality television program "The Biggest Loser." Mastrov is also an avid investor in the health and fitness movement worldwide.