Spend enough time at a health club or gym these days, and you're bound to overhear someone discussing core strength. The idea behind this new exercise buzz word is that the muscles surrounding your trunk--the ones that help you breathe and hold up your spine--need to be every bit as strong as your biceps or quadriceps. Indeed, says Wendell Liemohn, an exercise scientist at the University of Tennessee, "if you don't have a strong core, then moving your arms and legs won't be as efficient."
What that means in practical terms depends a lot on how physically active you are. Star athletes who have not built up their core strength have slower reaction times and are more prone to injury. Office workers whose trunk muscles have turned to flab behind their desks are apt to suffer chronic back pain. Older folks with poor core strength are likely to lose their balance and fall.
The prevailing wisdom among gym rats used to be that the best measure of core strength was how many sit-ups and push-ups they could do. That's wrong on two counts. Sit-ups and push-ups primarily work the muscles on the front side of the trunk, leaving those of the back weak and unengaged. It is also very easy to cheat at sit-ups by allowing hip muscles, and not the abdominals, to do the work. A properly executed crunch may not be as impressive as a sit-up, but the goal is to isolate and strengthen the muscles of the abdomen, not to show off. All you really need to do, after lying flat on your back on the floor, is raise your shoulders an inch or two in the air and slowly lower them 15 to 20 times. Keep your belly button pulled in; you'll notice the difference right away. (Push-ups are still O.K.)
First-time exercisers often forget their lateral abdominals--the muscles that sit beneath your love handles. Diagonal crunches, in which you sit up while twisting the abdomen, help develop these important muscles. Here's another good exercise that puts less stress on the spine: lie on your side and, resting your forearm on the ground for balance, lift your whole body off the floor; hold that position for 20 to 30 seconds. The key is to keep your hips, legs and back as straight as you can.
One exercise that is particularly effective for the back is the quadruped. Facing the floor on hands and knees, extend your right arm and left leg out from your trunk and hold that position for a few seconds. Repeat with your other arm and leg; make sure you keep your spine straight and don't let your abdomen sag. If that's too hard, you can also do this exercise while lying flat on your stomach. For something more challenging, try extending an opposing arm and leg while balancing on your stomach on a physiotherapy ball.
You don't have to belong to a gym to build up your core strength. There are excellent yoga, Tai Chi and Pilates exercises that you can do at home, as well as all manner of exercise gadgets you can buy, such as the Reebok wobble board or the Bosu half dome. The point is to find something that works for you. "Basically, all you really need is a mat and a floor," says Miriam Nelson, an exercise scientist at Tufts University and author of the Strong Women series. But if a class or gadget gets you motivated, then go for it. Your body--especially your back--will be glad you did.