Are there placebo or nocebo effects in balancing performance?

Abstract

Placebo and nocebo effects could influence the perceived, actual, or both postural stabilities. Therefore, this experiment examined whether postural stability is susceptible to placebo and nocebo effects. Driven by expectations, these cognitions could influence the motor stability of people in physical rehabilitation and those with motion instability. We randomly assigned 78 participants to a placebo, nocebo, or control group. Then, we applied a sham sports cream with positive, negative, or neutral instructions about its impact on balance. Next, we tested postural stability with a modified version of the Modified Clinical Test of Sensory Interaction in Balance, including standard, proprioceptive, visual, and vestibular tests before and after the intervention. Further, we measured expected and perceived performance with visual analog scales and assessed trait anxiety, change in state anxiety, optimism, holistic thinking, persistence, and cooperation with questionnaires. The intervention did not affect actual test performances; similarly, trait and state variables and expectations did not have an impact. Furthermore, the experimental manipulation and trait and state variables did not significantly affect perceived performance. However, the association between expectation and perceived performance was strong (ϱ = 0.627, p < 0.001). These findings suggest that postural stability is not susceptible to placebo and nocebo influences. Still, there is a dissociation between objective and subjective performance, showing that expectations impact perceived but not actual performance, which could fuel motivation in rehabilitation settings.

Keywords: Balance; Expectations; Nocebo; Placebo; Postural stability.

Fig. 1

Flowchart of the experiment. Note: 2. and 4. step was carried out in a separate room by a blinded experimenter

Fig. 2

Postural stability performance of the experimental groups pre- and post-intervention in the standard test type. Note: The error bars reflect 95% CI

Fig. 3

Postural stability performance of the experimental groups pre- and post-intervention in the proprioceptive test type. Note: The error bars reflect 95% CI

Fig. 4

Postural stability performance of the experimental groups pre- and post-intervention in the vision test type. Note: The error bars reflect 95% CI

Fig. 5

Postural stability performance of the experimental groups pre- and post-intervention in the vestibular test type. Note: The error bars reflect 95% CI

Fig. 6

Perceived performance of the three experimental groups. Note: The error bars reflect 95% CI

Fig. 7

The association between expected and perceived performance