Is the benefit of exercise a placebo effect?

The next time you're doing the housework, try donning a tracksuit, cranking up the Rocky sound-track and viewing the whole thing as an exercise session – doing so could have a positive effect on your health.

That's according to Alia Crum and Ellen Langer, who assessed the health of 84 female hotel cleaners, all of whom worked between 32 to 40 hours per week, cleaning approximately 15 rooms per day.

The researchers then told half the cleaners, via verbal presentations, handouts and posters, that the cleaning work they perform counts as exercise and means they effectively lead an active lifestyle, easily fulfilling government recommendations for daily exercise. The remaining cleaners acted as controls.

A month later the health of the cleaners was assessed again. Crucially, those who had been reminded how much exercise they engage in at work, showed health improvements in terms of weight, body mass index, body-fat, waist-to-hip ratio and blood pressure. The control cleaners showed no such improvements.

What caused this health boost? Those cleaners reminded that their work counted as exercise didn't change their smoking, drinking or eating habits over the month, nor did they start exercising more in their spare time. However, as intended, the intervention did lead them to perceive that they engaged in more exercise at work.

"These results support our hypothesis that increasing perceived exercise independently of actual exercise results in subsequent physiological improvements", the researchers said.

In the same way that some medicines work not because of any particular ingredient, but because of patients' belief in their healing power, the researchers concluded their findings show some of the benefits of exercise are also related to beliefs – otherwise known as the placebo effect.

Further reading

Crum, A.J. & Langer, E.J. (2007). Mind-set matters. Exercise and the placebo effect. Psychological Science, 18, 165-171.