Positive verbal suggestion optimizes postural control

Bernardo Villa-Sánchez,Michele Tinazzi,Mirta Fiorio,Mehran Emadi Andani,Giulia Menegaldo

doi:10.1038/s41598-019-42888-2

Abstract

Balance is a very important function that allows maintaining a stable stance needed for many daily life activities and for preventing falls. We investigated whether balance control could be improved by a placebo procedure consisting of verbal suggestion. Thirty healthy volunteers were randomized in two groups (placebo and control) and asked to perform a single-leg stance task in which they had to stand as steadily as possible on the dominant leg. The task was repeated in three sessions (T0, T1, T2). At T1 and T2 an inert treatment was applied on the leg, by informing the placebo group that it was effective in improving balance. The control group was overtly told that treatment was inert. An accelerometer applied on participants’ leg allowed to measure body sways in different directions. Subjective parameters, like perception of stability, were also collected. Results showed that the placebo group had less body sways than the control group at T2, both in the three-dimensional space and in the anterior-posterior direction. Furthermore, the placebo group perceived to be more stable than the control group. This study represents the first evidence that placebo effect optimizes posture, with a potential translational impact in patients with postural and gait disturbances.

Highlights

The placebo effect is a beneficial outcome that follows the administration of a treatment and that is not to be ascribed to active ingredients but to the words, contexts and beliefs that surround the treatment and that can induce psychological and neuronal changes in the recipient’s brain[1]
Post-hoc comparisons showed that in the placebo group postural sways were lower at T1 (−0.79 ± 0.16) and at T2 (−0.94 ± 0.12) compared to T0 (0.0 ± 0.26), whereas in the control group no significant effect was found across sessions (T1: 0.23 ± 0.52, T2: 0.50 ± 0.64, p > 0.843)
Post-hoc comparisons showed that the placebo group had lower relative leg angle (RLA)-AP values at T1 (−0.81 ± 0.16) and at T2 (−1.02 ± 0.13) than at T0 (0.0 ± 0.26) and at T2 compared to T1 (p = 0.042, d = 1.01), whereas in the control group no significant effect was found across sessions (T1: 0.28 ± 0.59, T2: 0.64 ± 0.70, p > 0.315)

Summary

Introduction

The placebo effect is a beneficial outcome that follows the administration of a treatment and that is not to be ascribed to active ingredients but to the words, contexts and beliefs that surround the treatment and that can induce psychological and neuronal changes in the recipient’s brain[1]. We aimed at investigating whether the placebo effect can influence a very important component of human motor functions, like balance control. We developed a new custom-made user-friendly device consisting of a sensor attached to the leg that allows a fine-tuned detection of body sways in different directional planes, without any platform or unwieldy equipment. This feature makes it practically useful in future studies aiming at exporting this paradigm outside the laboratory to improve balance control in patients affected by postural deficits or in gait disorders in www.nature.com/scientificreports/. We hypothesized that subjects of the placebo group would enhance balance control after the procedure compared to the control group

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Conclusion