People who think they're getting a good workout obtain more benefits than those who perform the exact same activities but don't think what they are doing is exercise, according to the findings of a study by Harvard researchers. These results support the idea that the benefits of exercise may involve a placebo effect.

Hotel cleaners who were told that their work of cleaning roughly 15 rooms each day was enough physical activity to maintain a healthy lifestyle were more trim and fit four weeks later than their peers who weren't given this message, Dr. Ellen Langer and her student Alia J. Crum report in the February issue of Psychological Science.

While the placebo effect of fake pills is widely accepted, Crum and Langer note, no one has yet studied whether the belief that exercise is maintaining fitness might exert a kind of placebo effect as well.

To investigate, the researchers recruited at 84 female housekeepers working at seven different hotels. Workers in four of the hotels were told that the exercise they got on the job met or exceeded the Surgeon General's activity recommendations for a healthy lifestyle, while those in the three other hotels were not told anything. Several measures of participants' fitness and health were taken at the beginning of the study and four weeks later.

Before the study started, about two-thirds of all participants said they didn't exercise regularly, while one third said they didn't exercise at all. After four weeks, 79.7 percent of the women in the informed group said they exercised regularly. They also lost 2 pounds, on average; lowered their blood pressure by 10 percent; and showed reductions in percentage of body fat, body mass index, and the size of their waists in relation to their hips.

All of these changes were significantly greater than those seen in the group who weren't told that their work was good exercise.

One possible explanation could have been that women in the informed group became more active and ate more healthily, the researchers note, but they found that this was not the case, making it unlikely that the fitness improvements were due to changes in behavior.

"These results support the hypothesis that exercise affects health in part or in whole via the placebo effect," Crum and Langer write. "Whether the change in physiological health was brought about directly or indirectly, it is clear that health is significantly affected by mind-set."

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