Placebo and nocebo effects occur in response to subjective expectations and their subsequent neural actions. Research shows that information shapes expectations that, consequently, influence people's behaviour. In this study, we examined the effects of a fictive and inert green colour energy drink provided for three groups (n = 20/group) with different information. The first group was led to expect that the drink augments running performance (positive information), the second group was led to expect that the drink may or may not improve performance (partial-positive information), while the third group was told that earlier research could not demonstrate that the drink improves performance (neutral/control). At baseline, the three groups did not differ in their 200-m sprint performance (p > .05). One week later, 20-min immediately after ingesting the drink, all participants again ran 200 m. The positive information group increased its performance by 2.41 s, which was statistically significant (p < .001) and also perceived its sprint-time shorter (p < .05) than the other two groups. A better performance (0.97 s) that approached but did not reach statistical significance was also noted in the partial-positive information group, and a lesser change (0.72 s) that was statistically not significant was noted in the neutral information control group. These results reveal that drinking an inert liquid, primed with positive information, changes both the actual and the self-perceived time on a 200-m sprint. The current findings also suggest that the level of certainty of the information might be linked to the magnitude of change in performance.
Keywords: Athlete; conditioning; exercise; expectation; placebo.