For exercise novices, not much, according to one study, which found that women who exercised in front of a mirror felt worse than women who exercised without them.
"Placing mirrors in exercise centers may need to be reconsidered, especially in centers that are trying to attract exercise initiates," said the study in the American Psychological Association journal Health Psychology.
The researchers at McMaster University in Hamilton, Ontario, looked at 58 sedentary women with an average age of almost 21. The women first answered questions about how they felt their bodies looked, how confident they were in their ability to ride an exercise bike, and what their mood was — whether, for instance, they felt "calm" or "worn-out."
The women rode the exercise bike twice, at a moderate intensity, for 20 minutes, one week apart. In one ride, they were in a mirrored room; in the other, the mirrors were covered by curtains.
After each ride, the women answered again the same sort of questions they had answered in the beginning.
When women rode while they could watch themselves in the mirror, they wound up feeling worse than they did when they could not look at themselves, the study found. For example, the mirrored rides left women feeling less calm and more fatigued.
This can't be simply a case in which women who watch themselves exercise come away with a worse opinion of their own bodies, said researcher Kathleen Martin Ginis, an associate professor of health and exercise psychology at McMaster. These women on average were not overweight, and even women with high body-image scores felt worse after exercising in front of a mirror, she said.
Other studies had found that gazing into a mirror tends to make a person feel worse, Ginis said.
It's not just the body, either. Even without exercise, periods of staring into a mirror make people start to think about their other flaws as well. "We tend to be quite critical," she said.
Exercise, on the other hand, tends to make people leave feeling better about themselves, and the study was designed to see if the exercise effect outweighed the mirror effect.
It did not, and the psychological tests picked that up. "This is the kind of thing where people come away thinking, 'I don't feel that great,'" she said.
Women who hadn't exercised before typically have low expectations of how well they would be able to exercise, and the women in this study probably felt the mirrors proved them right, the researchers said.
Although the study did not look at men, Ginis suspects men might have some of the same reactions, although less strongly, because men tend to be less self-critical than women.
The findings, published in June, indicate that health club operators should start changing their decor, the researchers said. "If a bout of exercise leaves a sedentary woman feeling worse than before she worked out, it will be difficult to persuade her to establish a regular exercise program," they said.
This fits the experiences of Curves International, a fast-growing chain that focuses on women, especially those who are not competitive. Members don't want mirrors, said founder Gary Heavin. "When we didn't put them in, they could concentrate on having fun," he said.
However, the bad experience with mirrors may not be true of more advanced exercisers, the study said. Other researchers have found that highly active women who exercised in front of a mirror felt better for it, possibly because they got to show themselves how good they did.
And Ginis is not about to bring upon herself the amount of bad luck that would develop if every health club in North America trashed its mirrors on her say-so. Mirrors are necessary equipment that help people such as weight trainers confirm they are doing their moves properly, she said. She suggested that clubs create mirror-free zones for women who are getting started.
By Ira Dreyfuss