Researchers provide evidence that the placebo effect is relevant to physical activity as well as medical conditions.
Researchers found that "sporty" adults who believed that 30 minutes of cycling would do them good felt that the activity was less strenuous, compared with sporty adults who had more negative expectations.
Among less sporty adults, researchers found that simply believing that a compression shirt would boost their cycling performance led to a reduction in perceptions of exertion, suggesting that the "placebo effect" may not be limited to medical outcomes.
Study leader Hendrik Mothes, of the Department of Sport Science at the University of Freiburg in Germany, and colleagues recently reported their findings in the journal PLOS One.
We have all heard that exercise is good for us. Current guidelines recommend that adults engage in at least 75 minutes of vigorous-intensity aerobic activity or 150 minutes of moderate-intensity aerobic activity every week, in order to improve or maintain health.
But it may come as no surprise that fewer than half of us are meeting these exercise guidelines.
According to Mothes and team, previous research has indicated that people's perceptions of how strenuous exercise is influences how they respond to physical activity.
"Negative affective responses, in turn, decrease long-term exercise motivation and participation," write the authors. "If one wishes to counteract the detrimental effects of a sedentary lifestyle, it is thus important to understand factors that affect perceived exertion in exercising individuals."
Testing the placebo effect
In medical research, the placebo effect is defined as a phenomenon whereby a placebo - a "sham" treatment that is portrayed as real - leads to improvements in a patient's condition.
For their study, the researchers sought to determine whether the placebo effect has a role to play in expectations of physical exertion.
To reach their findings, Mothes and colleagues enrolled 78 men and women, all aged between 18 and 32 years, and asked them to take part in two exercise tasks, completed 1 month apart. Each task involved riding a stationary bicycle-ergometer for 30 minutes.
Before the first task, participants were randomly assigned to one of two groups. One group was shown a series of short films that emphasized the positive effects of cycling, while the other (control) group was shown short films that played down the benefits of cycling.
For the second task, all subjects were required to wear a compression T-shirt produced by a popular sports brand. Again, participants were randomized to one of two groups.
One group viewed short films stating that the compression shirt can help to boost cycling performance, while others (the controls) watched short films claiming that the shirt reduced sweating.
"What the participants did not know was that we used these film clips with the aim of influencing their expectations of the coming cycling session," notes Mothes.
Before each exercise task, participants were asked to report how athletic they considered themselves to be. Every 5 minutes during their task, subjects were asked to report how strenuous they felt the exercise was.
Reduced perceptions of exertion
Looking at the results from the first task, the team found that subjects who had more positive expectations of the cycling task and who considered themselves to be more athletic felt that the exercise was less strenuous, when compared with athletic individuals in the control group.
The team identified no link between positive expectations and reduced perceptions of exertion among subjects who did not consider themselves to be athletic.
In the second task, the researchers found that non-athletic adults who believed the compression shirt would improve their cycling performance felt that the exercise task was less strenuous, compared with non-athletic adults who believed that the shirt would reduce sweating.
"Merely the belief that the shirt would help, did help the 'unsporty' subjects to have a lower perception of strenuousness during the exercise," says Mothes.
According to the researchers, their results indicate that the placebo effect may be just as relevant for physical activity as it is for medical conditions.
"Not least, the findings impressively show for all those who don't consider themselves to be great sportsmen and [sports]women - the right product really can make sport more pleasant, if 'only' you believe in it."