Many people with back pain are tempted to limit their activity, fearing that a workout will make the problem worse. But a new study shows they may be better off doing more exercise, not less, to help relieve back pain.

Exercising four days a week appears to be the magic amount, according to Canadian researchers from the University of Alberta, who presented their findings at the 2009 American College of Sports Medicine conference in Seattle.

Scientists studied 240 men and women with chronic lower back pain over a 16-week period, splitting them into groups who exercised with weights two, three or four days a week. There was also a control group that did not exercise at all.

Participants in the study were doing exercises like machine leg presses, leg curls, free weight bench presses, free weight arm curls and abdominal crunches.

Researchers found that those who worked with weights four days a week had 28 percent less pain, 36 percent less disability and 28 percent better quality of life, defined as general physical and mental well being, than those who hit the gym only two or three days a week.

The level of pain decreased by 18 percent when people exercised three days a week and by 14 percent if they hit the gym two days a week. The quality of life rose by 22 percent for those working out three days a week and 16 percent for two days.

The lead author of the study, Robert Kell, PhD, an assistant professor of work physiology in the Department of Social Sciences at the University of Alberta, in Edmonton, says these results are important because there is often a fear-avoidance cycle at work with people in pain where they choose to stop moving.

“This seems like common sense because then the pain stops,” Kell says. “However, if the person proceeds along this path they become very de-conditioned or sedentary, which commonly worsens their condition over time and leads to other health problems. In order for rehabilitation to work, the person with lower back pain or arthritis needs to push through the initial pain. If they do this, the pain will generally subside over time and subside to a greater degree than if they rested.”