When it comes to the core, strength is really synonymous with stability. You want your torso -- your body's center of gravity -- to be strong enough to keep your whole body balanced. And while athletes obviously need this kind of stability in order to perform at high intensity, the rest of us need it just to get through everyday activities. "Let's say you're at a crosswalk. You twist to press the button, balance on one foot while you step off the curb, jump over a pothole, walk across the street and step back up on the curb on the other side. You've just utilized every bit of your core," says Bugarin. When the core is strong, it holds the body in correct alignment so you can react and move quickly without pain.

Even the simplest activities -- like focusing on maintaining good posture and practicing better balance -- will help strengthen and stabilize your core. But to really make a difference, you'll need to work at it. Here are a few moves that will help you start building a stronger, safer, more functional core.

The plank
Lie on your stomach and then prop yourself up on your toes, elbows and forearms. Lift your body off the floor into a straight line, stomach pulled in, back lengthened and not arched. Hold this position for at least 15 seconds, working up to being able to hold it for a full minute. Rest and repeat two more times.

Balance and reach
Balance while standing on your left leg. Bending your left knee, take both hands and reach down next to your left knee as if you were picking something up. Then, keeping your arms straight, bring your arms across your body and up past your right shoulder, as if you were lifting something and placing it up high. Repeat eight times on each side.

Lying arm-and-leg reach
Lie on your back with your legs and arms extended straight up (so your body is making a "U" shape). Pull in your abs and slowly lower both legs and both arms toward the floor. As soon as you feel your lower back start to lift off the floor, raise your arms and legs back up. Do 12 repetitions.

Suitcase squat
Stand with your feet apart at a shoulder-width distance and hold a dumbbell (start with five pounds and increase if that feels too easy) in your right hand. Bend your knees (keeping weight on your heels) and lower your buttocks as far as is comfortable, then stand back up. Do 10 repetitions, then switch the dumbbell to your left hand and do 10 more. Holding the weight on only one side forces you to engage the oblique muscles (on your sides) as well as the back.

Core stretch
Get down on all fours on your hands and knees. Pull your stomach in, drop your head and arch your back upward -- like a cat. Then reverse the position, lifting your head and buttocks and arching your back inward. Move slowly back and forth between the two positions to stretch and loosen the muscles in the back and abs.