Studies on the placebo effect have shown that positive expectations improve postural control and motor performance and reduce perceived fatigability and discomfort. This study was aimed at investigating whether joint flexibility could be improved by a placebo procedure making use of sham transcranial direct current stimulation (tDCS). Thirty young healthy volunteers (age=22.3±1.7) took part in two experimental sessions, one week apart: a placebo condition and a control condition. The order of the sessions was balanced across participants. At the beginning of the first session, positive expectations were generated by verbal suggestions on the advantages induced by tDCS on motor performance. Hamstring flexibility was measured by a Sit and Reach Test (SRT) in three blocks, interspersed with 5 minutes of mobility exercises. In the placebo condition, but not in the control condition, mobility exercises were performed during the application of sham tDCS. In addition to SRT, subjective parameters of perceived exertion and pain, and treatment expectations and efficacy were measured by means of visual-analogue or numeric-rating scales. Results revealed that in both conditions, positive expectation reduced perceived exertion and pain during SRT. By contrast, the efficacy of placebo on hamstring flexibility showed an order effect: a significant increase of flexibility occurred only when the placebo condition was administered as second session one week after the explanation of verbal suggestions. A second experiment testing the role of timing as a function of the baseline levels of flexibility is ongoing. These effects have potential implications to foster post-trauma recovering and motor skill learning.

Positive expectations need time to improve joint flexibility

Luca Falciati
Writing – Original Draft Preparation
;
Silvia Rio;Claudio Maioli;Francesco Negro;Debora Brignani
2023-01-01

Abstract

Studies on the placebo effect have shown that positive expectations improve postural control and motor performance and reduce perceived fatigability and discomfort. This study was aimed at investigating whether joint flexibility could be improved by a placebo procedure making use of sham transcranial direct current stimulation (tDCS). Thirty young healthy volunteers (age=22.3±1.7) took part in two experimental sessions, one week apart: a placebo condition and a control condition. The order of the sessions was balanced across participants. At the beginning of the first session, positive expectations were generated by verbal suggestions on the advantages induced by tDCS on motor performance. Hamstring flexibility was measured by a Sit and Reach Test (SRT) in three blocks, interspersed with 5 minutes of mobility exercises. In the placebo condition, but not in the control condition, mobility exercises were performed during the application of sham tDCS. In addition to SRT, subjective parameters of perceived exertion and pain, and treatment expectations and efficacy were measured by means of visual-analogue or numeric-rating scales. Results revealed that in both conditions, positive expectation reduced perceived exertion and pain during SRT. By contrast, the efficacy of placebo on hamstring flexibility showed an order effect: a significant increase of flexibility occurred only when the placebo condition was administered as second session one week after the explanation of verbal suggestions. A second experiment testing the role of timing as a function of the baseline levels of flexibility is ongoing. These effects have potential implications to foster post-trauma recovering and motor skill learning.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11379/620225
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