The present project will evaluate through a randomised controlled clinical trial with 6-month follow-up, the efficacy and cost-utility (6-month time horizon) of the multicomponent FIBROWALK programme in an online (i.e., FIBRO-On) and outdoor (i.e., FIBRO-Out) adjunctive to usual care (HC) format, as compared to HC. In order to determine the mechanisms of action of the clinical effects of the interventions studied 6 months after the start of treatment, pre-post changes will be evaluated in various psychological variables considered to be mediators from a theoretical point of view, as well as in immuno-inflammatory markers with evidence of alteration in FM and/or potentially modifiable by the interventions proposed (i.e. IL-6, CXCL8, IL-17A, IL-4, IL-10, high-sensitivity C-reactive protein). In the field of personalised treatment in chronic pain, the design of the present study with 3 treatment branches will also make it possible to establish whether certain patient profiles or baseline psychobiological characteristics can predict the short- and medium-term clinical response to the treatments studied.

Introduction: The On&Out study is aimed at assessing the efficacy, cost-utility and immuno-inflammatory underpinnings of the FIBROWALK multicomponent intervention conducted in two different settings: online (FIBRO-On) or outdoors (FIBRO-Out). Both interventions have proved to be efficacious in the short-term but there is no study assessing their comparative efficacy nor their long-term effects. This study will also evaluate the cost-utility (6-month time-horizon) and the effects in blood biomarkers level of both interventions for the first time. The objectives of this 6-month, randomized, controlled trial (RCT) are (i) to examine the efficacy and cost-utility of adding FIBRO-On or FIBRO-Out to treatment-as-usual (TAU) for individuals with fibromyalgia; (ii) to identify pre-post differences in levels in blood biomarkers in the three study arms and (iii) to analyze the role of some psychological process variables as mediators of 6-month clinical outcomes. Methods and analysis: Participants will be 225 individuals with fibromyalgia recruited at Vall d'Hebron Institute of Research (Barcelona, Spain), randomly allocated to one of the three study arms: TAU vs TAU+FIBRO-On vs TAU+FIBRO-Out. A comprehensive assessment to collect functional impact, pain, fatigue, depressive-anxiety symptoms, physical function, kinesiophobia, pain catastrophism, quality of life, costs, and psychological process variables will be conducted pre-intervention, at half of the intervention (6 weeks, post-intervention (12 weeks), and at 6-month follow-up. Changes in immuno-inflammatory biomarkers (i.e. IL-6, CXCL8, IL-17A, IL-4, IL-10, and high-sensitivity C reactive protein) and Brain-Derived Neurotrophic Factor will be evaluated in 50% of the sample at pre- and post-treatment. Linear mixed-effects models using restricted maximum likelihood, mediational models and a full economic evaluation applying bootstrapping techniques, acceptability curves and sensitivity analyses will be computed.

Inclusion Criteria:

1. Patients of both sexes, between 18 and 65 years of age.
2. Diagnosis of fibromyalgia according to the ACR 2010/2011 criteria.
3. Understanding Spanish.

Exclusion Criteria:

1. Psychological treatment (within the last year) or current.
2. Comorbid presence of severe mental disorder (e.g. schizophrenia) or other terminal clinical conditions or scheduled treatments that may interrupt study follow-up.
3. Inability to complete the weekly sessions/modules of the programme on a regular basis.
4. Being in litigation with the health system with the aim of obtaining a permanent leave of absence.