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Something more specific for the abs to crunch on

Position variations have different effects on the body, a study finds. Customize sit-ups to individual needs.

August 25, 2003|Elena Conis | Times Staff Writer

Abdominal exercises have long been a workout staple, and each form -- the crunch, the full sit-up, with or without an exercise ball -- has its staunch supporters.

Now, researchers have studied the mechanics of the various forms and found that the moves do vary in effectiveness. But which works best, they say, depends on your needs.

"Strong abdominals are critical for all kinds of physical activity," said Raymond Chong, an assistant professor of physical therapy at the Medical College of Georgia in Augusta. Abdominal muscles support the spine and help maintain good posture. When they're weak, the back compensates and the heart works harder, he said, making even simple activities such as walking or standing straight harder than they should be.

In an effort to reveal how sit-ups affect muscles from the neck to the legs, and not just the abdominals, Chong and his colleagues asked 15 volunteers to perform six types of exercises: crunches and full sit-ups with exercise balls, without exercise balls, and then with an assistant to hold the balls steady. Sensors attached to their bodies recorded intensity and duration of muscle contractions.

The researchers found that each type of move had different effects on the body. Because of that, they said, exercisers should customize their sit-ups. For instance, soft-surface sit-ups or crunches may be the best exercise for people who are just getting in shape or who suffer from muscle strain. They require less effort than exercising on a hard floor but offer a good workout at the same time.

Chong said he and his colleagues expected that doing sit-ups on something soft would be like "walking on the beach. It's more difficult to walk on sand." But a soft surface -- like a ball, bed or turf -- actually makes it easier for the pelvis to rotate, which in turn makes it easier to lift the trunk.

This is good news, said Chong, because "many people like to do sit-ups on soft surfaces -- it's more gentle on the hips and back." Firm surfaces are much rougher on the body. "They apply force back at you," he added.

Full sit-ups on firm surfaces might work best for those seeking to maintain well-developed abs, while crunches or ball-assisted exercises might be preferable for those just starting out, he said.

Although not all exercises are good for all people, the only move to avoid is one done dangerously, he said, such as by whipping the neck up and forward, which can exacerbate tension headaches and neck strain. "It's OK to do the wrong movement and not get a workout. But it's another thing to be doing it in an unsafe way and put yourself at risk of injuries."

Chong recommended having someone who understands sit-ups show you how to do them correctly. Especially, he added, if you're a novice.

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