Positive verbal suggestion optimizes postural control

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.

A comparison of placebo and nocebo effects on objective and subjective postural stability: a double-edged sword?

“…Reduced COP movements during quiet standing have previously been described in healthy young adults following a placebo procedure (Villa-Sánchez et al, 2019). In agreement with our hypothesis and previous literature, our findings confirm that participants in the placebo group exhibited a reduced range (greater precision achieved by the postural control system) of the COP and concomitantly increased perceived stability after expectation manipulation.…”

“…Additionally, our placebo procedure may have enhanced positive affect and resulted in increased effort. However, in a previous study, positive verbal suggestions elicited a reduction in postural sway without any changes in balance effort (measured using the Borg 0-10 scale; Borg, 1982;Villa-Sánchez et al, 2019). Therefore, the relative contribution of increased effort and motivation on postural stability following a placebo procedure remain unclear.…”

“…Although placebo (analgesia) and nocebo (hyperalgesia) phenomena have been largely confined to the study of pain tolerance (Frisaldi et al, 2015 ), there is emerging evidence elucidating the application of these effects on motor and cognitive performance. In this regard, it is now well established that placebo effects can positively influence muscle force production (Fiorio et al, 2014 ; Villa-Sánchez et al, 2019 ), increase fatigue resistance (Piedimonte et al, 2015 ) and improve attention/vigilance (Colagiuri and Boakes, 2010 ). Despite convincing evidence that placebo related expectations can induce positive changes in several cognitive/motor functions, the potential effects of placebos on other important cognitive-motor functions that are essential to normal everyday functioning, such as balance performance, are less well understood.…”

“…Indeed, only one study has examined changes in postural control following a placebo procedure. Young adults who were made to believe that a placebo treatment was effective (application of an inert electrical device over the leg muscle) presented with reduced postural sway and perceived their balance control to be subsequently more stable when compared to a control group (Villa-Sánchez et al, 2019 ). These findings indicate that instead of being regarded as a bias to control for in randomized control trials, placebos could be deliberately utilized and combined with established approaches to increase therapeutic efficacy of balance interventions (Enck et al, 2013 ; Schwarz and Büchel, 2015 ).…”

Context matters: the psychoneurobiological determinants of placebo, nocebo and context-related effects in physiotherapy

“…Emergent studies have suggested a mechanical and neurophysiological mechanism (peripheral, spinal and supraspinal) as the base of the effects induced by the therapeutic interventions adopted by the physiotherapists [35][36][37]. Considering the supraspinal mechanisms, placebo and nocebo effects were indicated as important top-down modulators of patient's symptoms, mainly pain and motor performance [38][39][40][41][42][43][44], thus becoming elements that physiotherapists should attentively consider in their clinical practice [17].…”