Exercise has many benefits for health but easing hot flashes isn't on the list, a new study finds.

Researchers in the U.S. randomly assigned 142 women who were either approaching menopause or postmenopausal to continue their usual activities and 106 to do aerobic exercise three times a week for 12 weeks. The women kept diaries to record their hot flashes and night sweats — known as vasomotor symptoms — as well as how well they slept.

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Women in the exercise group did aerobic workouts three times a week for 12 weeks at a facility. (Jessica Hill/Associated Press)

The trial "provides strong evidence that aerobic exercise training in previously sedentary women does not significantly alleviate frequent or bothersome vasomotor symptoms," Barbara Sternfeld of Kaiser Permanente in Oakland, Calif. and her co-authors concluded in today's online issue of the journal Menopause, the journal of The North American Menopause Society.  

"However, exercise training improves fitness level, is safe and well-tolerated and may slightly improve subjective sleep quality and symptoms of insomnia and depression," the researchers said, based on the participants' responses to questionnaires.

The exercise group reported an average decrease of 2.4 hot flashes per day compared with 2.6 in the group that continued their usual activities.

The women in the exercise group were older and slightly less fit but otherwise similar to the others.

Exercise seemed to reduce hot flashes in white women but not in African-American women, a difference that the researchers speculated could result from racial differences in cardiovascular, metabolic or hormonal responses to exercise.

One limitation is that the study's authors relied on women to report hot flashes because there isn't a more precise tool available for use outside of laboratories.

It's also possible that different intensities, frequency or individualized exercise prescriptions could have a different effect, the researchers said.

While previous studies have been inconsistent, Sternfeld's team said their findings corroborate a recent Cochrane review, which also concluded that there was no evidence to support the use of exercise as an effective treatment for hot flashes and night sweats.

The study was funded by the U.S. National Institute on Aging, Eunice Kennedy Shriver National Institute of Child Health and Development, the National Center for Complementary and Alternative Medicine, Office of Research and Women's Health and the Indiana Clinical and Translational Sciences Institutes.

Several study authors have received research support or consulted for pharmaceutical companies.