Reconsidering Exercise: the Role of Expectations for Positive Health Effects of Acute Exercise

Abstract

Background: This study investigated whether the effects of acute exercise are the result of a placebo effect, i.e. different expectations towards the exercise. Methods: 78 subjects were tested in a double-blinded, randomized controlled design. Expectations regarding the health effects of a subsequent 30 min bicycle ergometry were manipulated in four groups through different videos. In addition, we measured expectations towards mood and health changes following exercise that already existed in participants before the experiment. Mood, anxiety, blood pressure and EEG were measured before and after the exercise. Perceived exertion was quantified during the activity. Findings: Results show that positive expectations following the experimental manipulation resulted in reduced perceived exertion during the activity (p < .01). In addition, most of the health effects of the acute exercise (increased mood, reduced anxiety, reduced blood pressure and characteristic changes in EEG) were dependent on expectations that already existed before the experiment. Discussion: This study supports the hypothesis that health effects of acute exercise are at least in part result of a placebo effect.