No matter what workout fads come and go, Kate Hudson knows what works for her: good old-fashioned cardio. Even though she's a fan of hitting the pavement, Hudson is often spotted leaving Los Angeles' YAS Fitness Center. The Spinning- and yoga-infused classes help Hudson keep her heart pumping and her muscles lean, instead of bulky. If comparable classes are not offered in your area, try to work both activities into your schedule every week. Spinning is a good alternative to long-distance running (plus, you can do it indoors even on the coldest days!) and yoga is a tried-and-true way to tone muscles.