Research pinpoints variations in sit-up techniques

Main Category: Obesity / Weight Loss / Fitness
Article Date: 16 Aug 2003 - 0:00 PDT

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Contact: Christine Hurley Deriso
cderiso@mail.mcg.edu
706-721-2124
Medical College of Georgia

Those with flabby tummies have probably heard lots of tips about the perfect sit-up. A Medical College of Georgia study has determined that no sit-up is perfect for everyone - but there are lots of techniques to meet individual fitness goals.

'Exercise should be tailored to the individual,' said Dr. Raymond Chong, an MCG assistant professor of physical therapy. An individualized approach is particularly important when developing an exercise program for someone with an injury or medical condition, as physical therapists routinely do, he noted.

Increasingly sophisticated tools are available to determine the effectiveness of exercises, and how appropriate they are for the individuals using them. Dr. Chong and four of his students used those tools this summer to study sit-ups from the inside out.

The group tested 15 healthy young adults performing six types of sit-ups: partial sit-ups (also called crunches, lifting the shoulders about six inches from a supine position) on the floor; full sit-ups (rising to a full lateral position) with knees bent at a 90-degree angle on the floor; crunches using an exercise ball with no assistance; full sit-ups using an exercise ball with no assistance; crunches using a ball held steady by an assistant; and full sit-ups using a ball held steady by an assistant.

In all positions, the study participants' arms were folded across their chest and their feet were stabilized. The exercise ball, a current trend in fitness, was soft, pliable and 70 centimeters in diameter. A metronome maintained a constant beat so that each sit-up was consistently timed.

The study participants did each type of sit-up eight times, with sensors attached that detected the electrical signals of each muscle contraction. The signals were fed into a computer so that the exact muscle activation of each sit-up could be measured and recorded.

The results surprised the researchers. For instance, they had theorized that considerable exertion would be needed to steady the ball with no assistance while doing sit-ups. But they found that the ball actually relieved effort.

'When you apply pressure against the floor, there is a ground reaction equal to the force that was applied,' Dr. Chong said. 'But the ball absorbs the pressure. We didn't predict the mechanical aid the ball would provide.'

They also found that full sit-ups are more strenuous than crunches.

'Crunches require less effort and less strain on the hip and lower back,' Dr. Chong said. Also, interestingly, crunches are harder on the neck. 'When the body is vertical (as during a full sit-up), the neck gets a break.'

The most strenuous sit-up is a full sit-up from the floor, he said, noting its activation of muscles in the abdomen, back, shoulders, hips and legs. The second-most strenuous is a full sit-up using the ball unassisted. Least strenuous are crunches on the floor, followed in order by crunches using a ball with an assistant, crunches using a ball without an assistant and full sit-ups using a ball with an assistant.

'I was quite amazed at the research results,' said senior physical therapy student Laurie Adkins, who participated in the research. 'It's nice to find out that different types of abdominal exercises target different muscles.'

Likewise, 'I was very surprised with the results,' said Kimberly Steele, also a student participant in the research. 'I've been an aerobics instructor for seven years and a personal trainer for three. I typically save the last 10 minutes of a class for abdominal work.' Now that she knows floor crunches are the least strenuous form of sit-up, she plans to modify her classes

This is exactly the kind of result Dr. Chong tries to inspire in his students. 'As science progresses, exercises can be better tailored and more effective,' he said. 'I challenge my students to give me the rationale and explain the science behind it. I stress to them, 'Show me what you're doing is working.''

He also emphasizes that more isn't necessarily better. For instance, a sedentary person beginning an exercise program should probably opt for crunches rather than full sit-ups, since they are less strenuous and less stressful on the hips and lower back. Those with neck pain should avoid crunches.

'The only bad exercise,' Dr. Chong said, 'is one that's unsafe.'