Sexy back

Basic weight-room rule: Work opposing muscle groups to prevent a strength imbalance that could cause injury. So why are you spending so much time developing your abdominals and all but ignoring the muscles that support your lower back? Many trainers see people doing hundreds of crunches without giving their lower back a second thought, says Gina Lombardi, a certified trainer in Woodland Hills, Calif.

Too bad, when you consider all that a strong low back has to offer -- including protection against back pain and better posture. And don't forget aesthetics: "No matter how toned your abs are, you'll look soft and flabby if there's no muscular development in your back," Lombardi says.

Lombardi has three back exercises for you to add to your arsenal. Her program begins with the alternating arm and leg lift -- "a great exercise for swimmers and golfers" -- because it requires the most strength and focus. Next, you'll do back extensions on a stability ball, a move that works muscles that provide support for your low back as well as the stabilizing muscles in your torso. Finally, you'll move to a hyperextension bench for a move guaranteed to zero in on those same muscles: "The only way to raise your upper body is by contracting your back muscles," Lombardi says. "You can't cheat."

For balanced spinal muscle strength and a sexy, sculpted look, Lombardi recommends doing these back moves at least two to three times per week. To work both sides equally, aim for a 1-1 ratio of ab to back exercises, she advises. "If you don't have a strong trunk -- and that includes both your abs and your back -- you're asking for problems."