Tuesday, April 24, 2007

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.
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Crum, A.J. & Langer, E.J. (2007). Mind-set matters. Exercise and the placebo
effect. Psychological Science, 18, 165-171.
http://dx.doi.org/10.1111/j.1467-9280.2007.01867.x

9 comments:

Anonymous said...

There's a parallel here with the importance of non-cognitive skills in the determination of labour market outcomes. Self-belief isn't a non-cognitive skill, but it is certainly a state of mind that would allow persistence and determination to have a more substantial effect.

Kevin Denny said...

Is self-belief the same as self-esteem? I think that has cropped up in the labour econ literature & Arnaud might be working on it too.

Kevin Denny said...
This comment has been removed by the author.
Peter Carney said...

I haven’t read the article but I get the feeling that this is less a placebo effect and more a Hawthorne effect. I may be wrong but it appears like a classic case -- involving hotel-accommodation workers in a study that appears interested in their health is likely to have an effect on their wider cognitions and subsequent health behaviours.

Anonymous said...

I disagree that this is more of a Hawthorne effect. The Hawthorne effect is about being made to feel important whereas the placebo is about changing beliefs. I think the hotel-cleaners got a placebo that made them believe their work constituted exercise. I don't think that their exercise production increased because they were made to feel more important.

In relation to self-belief and self-esteem, there is definitely a semantic difference. Self-esteem is can be framed as self-respect whereas self-belief is, I would argue, is more about having confidence in your abilities. I can see how both might be picked up on as being about having confidence in abilities though.

The salient point is that talking about self-esteem as a component of non-cognitive skills is quite controversial. Self-esteem (and locus of control) are by no means direct measures of persistence and determination. I know they are mooted to be proxies, but I honestly think that self-esteem and external locus of control enable persistence and determination, but persistence and determination are still quite distinct.

Peter Carney said...

I cannot agree Martin; I still believe the Hawthorne effect is at play here but even more important is the apparent misnomer with respect to the ‘placebo effect’.

The treatment wasn’t fake, false or misleading; factual information was asserted about the health benefits of their physical work. The treatment made the treated more cognizant of their health and the health benefits from their physical application. This, I suggest, induced a greater effort (more exercise) on their part both on and off the job and that this had a subsequent, direct and indirect, effect on other health issues like diet, attitudes, and such things.

In addition and in relation to the Hawthorne effect, I would hypothesise that the treatment group got more attention (they were told about the health benefits of their work) and were more aware of the purpose of the study (wouldn’t have been difficult to induce – “we’re interested in your weight, bmi, waistline… ”, “… oh, and be aware that your occupation has an effect on these measures…”) than the control group. So if one was looking for explanations outside of the effect of the treatment (as outlined above) I think Hawthorne makes more sense than placebo.

In conclusion, I should probably read the article.

Anonymous said...

Peter,

First of all I must apologise for my dodgy definition of the Hawthorne effect. The Hawthorne effect is not about being made to feel important, it is simply the "phenomenon of observing workers' behavior or their performance and changing it temporarily".

With this definition of the Hawthorne effect, and the indisputable fact that the experimenters did more than observe the hotel-cleaners, I think it is fair to rule out a Hawthorne effcet. The experimenters suggested that the cleaning work was a good form of exercise, so this is certainly something above and beyond a pure Hawthorne effect.

However, I do accept your point about the placebo effect not occurring. If we accept the advice given that the hotel-cleaning work amounted to the amount of exercise recommended by the government on a daily basis, then there is certainly no fake teatment, or in this case, fake advice.

So in conclusion, I argue that neither the Hawthorne nor the placebo effect applies. And once again, apologies for my originally incorect definition of the Hawthorne effect.

Peter Carney said...

Martin, I will add four points:

Your original definition wasnt completely incorrect.

Your new definition is somewhat incorrect.

To assert that there wasnt any Hawthorne effect you would need to have three groups: treatment, placebo treatment, and no treatment.

I think we should replicate the study!

I will conclude as before, if one was looking for explanations outside of the effect of treatment I think Hawthorne makes more sense than placebo.

Kevin Denny said...

I recall a story awhile ago that one could achieve some of the benefits of exercise just by visualizing it: i.e. you could think yourself thin.it was based on proper experiments etc