The blonde, peppy, and ageless fitness pro has been teaching classes since the early '80s, and in 1981 she was tapped to co-host Jack LaLanne’s fitness show. Since then she has gone on to build her own fitness empire, and unlike LaLanne’s never-changing appearance, her look has evolved as fitness trends have changed—you won’t see any legwarmers or big hair on her more recent work. She’s produced more than 80 workout videos and DVDs (selling more than 20 million copies), written books, and starred on her own fitness program. Austin, like most of the figures on this list, has parlayed her popularity and reputation as a fitness expert into advertising partnerships, working on behalf of Idaho potatoes, Sketchers, and Nature Made. She’s scheduled to have a new program air on Lifetime in 2011.