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Boosting the hypoalgesic effects of spinal manipulative therapy using conditioning and positive expectation: a randomised clinical trial

Grant number: 19/23356-1
Support Opportunities:Scholarships in Brazil - Post-Doctoral
Effective date (Start): October 01, 2021
Effective date (End): August 17, 2023
Field of knowledge:Health Sciences - Physiotherapy and Occupational Therapy
Principal Investigator:Thaís Cristina Chaves
Grantee:Helen Cristina Nogueira Carrer
Host Institution: Centro de Ciências Biológicas e da Saúde (CCBS). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil


The term "contextual effect" has been used to reinforce the view that the placebo effect should be understood as an effect related to the therapeutic context, and not restricted to the use of inert treatments. Thus, the placebo effect is inherent to any therapeutic context and also can be used to enhance the effects of treatment with active components. There is evidence of the effectiveness of manipulative therapy in the treatment of Chronic Low Back Pain (CLBP), however, for most physical therapy interventions, its effect is small. Thus, strategies to enhance the effects of this therapy, such as through the use of context factors, may contribute to better therapeutic outcomes. The literature describes conditioning or positive induced expectation models to favor the placebo effect. Although some previous studies have shown that expectation alone or associated with conditioning procedures may intensify hypoalgesic effects of therapies, no previous work has verified the isolated or associated hypoalgesic effect of conditioning and induction of expectancy on treatment in patients with CLBP undergoing manipulative therapy. Thus, the objective of this study will be to identify whether a conditioning procedure through surreptitiously downgrade of nociceptive stimulus intensity associated with positive induced expectation about treatment will result in greater hypoalgesic effects when compared to positive verbal suggestions (expectations) induced or expectation alone regarding the effects of manipulative therapy intervention in patients with CLBP. Methods: it will be a randomized clinical trial with blinded assessor. It will be investigated the effect of the use of a hidden conditioning procedure and the induction of positive expectancy on pain intensity after the administration of a manipulative therapy approach (active treatment). We will enroll 264 patients with nonspecific CLBP aged 18 to 65 years will participate in this study. The sample size calculation was based on a minimal difference between groups of 2 units on pain intensity and overall perception of improvement (primary outcomes). All patients will undergo 5 sessions of manipulative therapy in the lumbar spine, except the no treatment group (G3). In the first session, patients will be subjected to the inclusion and exclusion criteria and the calibration test to determine the thermal pain threshold, using the Q-sense equipment (Medoc), for the conditioning procedure. In the second treatment session, first the patients will be randomized to one of the three groups by a blinded assessor: hidden conditioning + expectations (G1) group; positive expectations only - group (G2) and neutral expectation group (G3). Following, participants will receive specific instructions to induce expectation in G1 and G2, and for G3, neutral instructions. Afterwards, patients will receive the pre-conditioning test (heat pain), then they will be submitted to the manipulative therapy (session 1) and again undergo the heat-conditioning post-testing. However, G1 will receive hidden conditioning (surreptitiously downgrade of nociceptive stimulus intensity) to reinforce the association between manipulative therapy and pain intensity reduction. The main hypothesis of this study is that the group undergoing hidden conditioning associated with positive induced expectation will have a higher hypoalgesic effect than the other groups immediate post treatment. (AU)

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