Strong legs are a great asset when it comes to performing powerful kicks in kickboxing class or biking that extra mile on your next ride. Plus, they just look great. In order to develop stunning legs, you need more than just aerobics, says trainer Cheryl Milson, co-owner of Premier Health Enhancement, an in-home fitness, nutrition and stress-reduction training service in Los Angeles. "We tend to focus on aerobics, but you shouldn't skimp on strength [training]." Milson notes another benefit of training the quads: "You want to work them to keep the muscle surrounding the knee joint strong to prevent injuries, which will improve your ability to perform in all areas, including sports."

Even though the quads get worked out during everyday activities like walking, it's not enough -- you need to strengthen them in the gym, says Milson. When you strengthen the quads, form is crucial. "Typically people are not concentrating on form enough to properly activate the quads," she says. For example, Milson advises to press through the heels when doing squats, and also to tighten the quad muscles like making a fist. Otherwise, you won't hit all the muscle fibers.