Dennis Ang of Wake Forest Baptist Medical Center in Winston-Salem, N.C., tracked 170 patients over 36 weeks. They took part in moderate activity, such as brisk walking 20 minutes a day.
The study, published in the journal Arthritis Care and Research, found patients who could stick out the walking program for 12 weeks had fewer symptoms.
"If they just sustained their level of physical activity past 12 weeks, their pain severity, which is a major symptom of fibromyalgia, would actually also get better," Ang said in a statement.
However, Ang warned people needed to ease into the walking by starting with a couple of weeks of very light exercise a couple of days a week.