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SATURDAY, Aug. 2 (HealthDayNews) -- Mirror, mirror on the wall, who's the fittest woman of all?

You may not get the answer you desire if you exercise in a gym where the walls are actually adorned with mirrors.

That surprising finding comes from a Canadian study in the journal Health Psychology. The research found sedentary women who exercised in front of a mirror for 20 minutes felt less energized, less relaxed and less upbeat and positive than women who exercised without a mirror.

The McMaster University study also found women who didn't exercise with a mirror felt less physically exhausted after a workout, while those who did their workout in front of a mirror reported no change in their levels of exhaustion.

The findings may provide insight into how best to encourage sedentary women to get physically active. Currently, standard guidelines for exercise promotion recommend that workout rooms have mirrors on at least two of four walls.

"As such, the recommended practice of placing mirrors in exercise centers may need to be reconsidered, especially in centers that are trying to attract exercise initiates," researcher Kathleen A. Martin Ginis says in a news release. "Certainly, if a woman leaves the gym feeling even worse than when she arrived, she will not be particularly motivated to continue exercising in the future."

Even women who felt good about their bodies experienced the negative effects while exercising in front of a mirror, so this isn't an issue only for women with poor body image, she notes.

The study included 58 university women who normally did less than 1 moderate or strenuous 15-minute workout a week. They were interviewed about their body image and their feelings before and after working out.

For the study, they rode a stationary bicycle at a moderate pace for 20 minutes. They wore loose-fitting shorts, a T-shirt and running shoes.

Further research in "real-world" exercise settings are needed to determine if this mirror-related negative effect is widespread, the researchers say.

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