Effects of strength training on conditioned pain modulation in patients with fibromyalgia: a prospective experimental study

SUMMARY OBJECTIVE: The aim of this study was to evaluate the conditioned pain modulation of patients with fibromyalgia and compare it to that of healthy individuals before and after 3 months of strength training. METHODS: This is a prospective experimental study consisting of two independent, non-randomized groups: fibromyalgia (n=10) and healthy control (n=10). The research was conducted in person at the Unidade Saúde Escola of the Federal University of São Carlos, Brazil, during the period of June 2023–June 2024. The conditioned pain modulation test was administered to all patients in both groups. Twice a week (for 3 months), patients with fibromyalgia performed three sets of each exercise, with 10 repetitions, 40 s of muscle tension, and a 60-s interval between the sets. Subsequently, we compared the conditioned pain modulation test using the Student's t-test. RESULTS: Significant between-groups differences (p≤0.05) and large effect sizes (d≥0.8) that were observed at baseline (at times 2, 3, and 4) were not observed after 3 months of strength training, indicating that the intervention was able to improve the conditioned pain modulation in patients with fibromyalgia. Although the within-group comparisons (pre- and posttreatment) showed an absolute difference of 6.35 in central sensitization, this was not statistically significant (p≥0.05) and had a small effect size (d=0.27). CONCLUSIONS: The conditioned pain modulation of fibromyalgia patients appears to become similar to that of healthy individuals after 3 months of strength training.