July 03, 2007

Study offers insight into your (lower) 'aching back'

by K.C. Jaehnig

CARBONDALE, Ill. -- So you're bent over your prize-winning daylilies harvesting the seeds, or you're under the hood of that classic '58 Chevy fine-tuning the engine when you hear the doorbell. You straighten up to answer it and YOUCH! Welcome to the world of low back pain.

Because people engaged in "flow activities" such as gardening or tinkering with a car lose track of time, they often remain in the same position for long periods, said Michael W. Olson, a kinesiologist at Southern Illinois University Carbondale.

"When you bend over at a certain trunk angle, the lower back muscles actually shut off," he said. "The ligaments in the lower back then support the trunk to keep you there, but they can only sustain you for so long.

"In this position, both the muscles and the ligaments have lengthened. When you stretch tissue, you squeeze out fluid. As water helps give structural support to the tissues, it actually adds strength to the tissues, so its loss means a loss of the ability to sustain the position. When you straighten up again, you feel that 'kink' in your back."

Sometimes it's more than a kink. Low back pain can range from an ache to a stabbing sensation and can limit movement or make it hard to stand up straight. According to the National Institute of Neurological Disorders and Stroke, it's the second most common neurological ailment in the country (after headache) and a major reason why people miss work.

With low back pain so prevalent, increasing both with age and with sedentary lifestyles, Olson has been taking a closer look at the ligament system. He wants to learn more about how it functions and about the interplay between it, the muscles and the nervous system.

In a small-scale, preliminary study performed in his lab over the last academic year, he found a way to measure how much stretching these tissues could take.

"We supported people at a 60-degree angle of trunk flexion from a standing position while they rested against an isometric dynamometer to measure the tension supplied by the ligaments in the lower back," Olson said.

"They were held in the position for 10 minutes — long enough for the muscles to remain shut off and for the ligaments to take over. Using a mathematical model we were able to quantify the amount of force the tissues were able to sustain over time."

That amount decreases the longer the position is held, which ups the chances of injury if people suddenly change position.

"Even a little movement is enough — it doesn't have to be big to cause damage," Olson said.

How much damage? Not much initially. The affected area becomes swollen and tender but responds to compresses, pain relievers and a break from the activity that caused the pain.

"But if you keep doing (the activity) on a regular basis, you will find the tissues don't recover in the same way," Olson cautioned.

"It's a cumulative effect. If you ignore the pain, you could be setting yourself up for later injury."

To protect your lower back while working around the house, garden or garage, Olson offered a few quick tips.

• Avoid bent-back lifting with good technique.

Lift with your knees by squatting, pulling in your stomach muscles and keeping your back straight. Keep the load close to your body.

• Take frequent breaks.

"Because squatting requires more energy than bending at the waist, when you're tired, you start stooping more," Olson said.

"When you have fatigue in the muscle system, the lower back tissues may become lax, setting up the possibility of instability in the back. Even if it seems like you're not exerting a lot of effort, switch positions or get up and walk around."

• Boost your fluid intake.

Remember that tissues lose fluid when stretched, reducing their strength.

"Water provides good support," Olson said.

• Alternate "stoop" work with other chores.

"If you perform tasks where you have to lean over for long periods of time, try to get some rest between them," Olson advised. "Some of the low back tissues don't recover fully even after eight hours."