Anette Larsson , Annie Palstam, Monika Löfgren , Malin Ernberg, Jan Bjersing, Indre Bileviciute-Ljungar, Björn Gerdle, Eva Kosek, Kaisa Mannerkorpi
Institute of Neuroscience and Physiology, Section of Health and Rehabilitation, Physiotherapy, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. E-mail: anette.e.larsson@vgregion.se
DOI: 10.2340/16501977-2278

Objectives: Resistance exercise results in health benefits in fibromyalgia. The aim of this study was to determine the factors that mediate change in muscle strength in women with fibromyalgia as a result of resistance exercise.
Methods: Sixty-seven women with fibromyalgia (age range 25–64 years) were included. Tests of muscle strength and questionnaires related to pain, fear
avoidance and physical activity were carried out. Multivariable stepwise regression was used to analyse explanatory factors for change and predictors for final values of knee-extension force, elbow-flexion force and hand-grip force.
Results: Change in knee-extension force was explained by fear avoidance beliefs about physical activity at baseline, together with change in pain intensity, knee-extension force at baseline, age and body mass index (BMI) (R2=0. 40, p = 0. 013). Change in elbow-flexion force was explained by pain intensity at baseline, together with baseline fear avoidance beliefs about physical activity, BMI and elbow-flexion force at baseline (R2 = 0. 32, p = 0. 043). Change in hand-grip force was explained by hand-grip force at baseline, change in pain intensity and baseline fear avoidance (R2 = 0. 37, p = 0. 009). Final muscle strength was predicted by the same variables as change, except pain.
Conclusion: Pain and fear avoidance are important factors to consider in rehabilitation using resistance exercise for women with fibromyalgia.

Women with fibromyalgia (FM) suffer from pain, impaired physical capacity and activity limitations and engage more in sedentary activities and less in physical activities of all intensities. Pain in FM commonly builds hinders for all exercise at a strenuous level and can also raise fear avoidance beliefs about physical activity. As activity-induced pain is a common feature in FM, this might be a reason for the avoidance of heavier physical activities such as resistance exercise. We found it of interest to study which factors might have an influence on a patient’s ability to perform resistance exercise and to increase muscle strength. The results, when analyzing three muscle groups (knee-extension, elbow flexion and hand grip) show that decreased pain and low fear avoidance, among other variables, contributed to the change in muscle strength following the resistance exercise intervention. This emphasizes the importance of adjusting the program to each individual and also stresses the importance of carefully selected loads and exercises intended to increase muscle strength without increasing pain and fear avoidance. Using person-centered principles in rehabilitation is suggested to be effective in managing pain and changing avoidance behavior towards physical activity.