It has been suggested that low physical fitness is a contributor to pain in fibromyalgia and that exercise-related beliefs play a role in the persistence of this association. Yet the association between physical fitness and pain is hardly explored in detail.
The aim of this exploratory study in patients with fibromyalgia was to investigate the association of physical fitness levels with self-reported and experimental pain as well as with pain catastrophizing and activity-avoidance beliefs.
Physical fitness of 18 patients with fibromyalgia was examined using maximal ergocycling and the 6-minute walking test (6MWT). Pain intensity was assessed using self-report scales and quantitative sensory testing.
A reduced walking distance on the 6MWT was correlated with more severe self-reported pain on the Fibromyalgia Impact Questionnaire (r = -0.52, P < 0.05). Recovery of heart rate after ergocycling was correlated with cold pain thresholds (r = 0.70, P < 0.01), pressure pain thresholds (r = -0.70, P < 0.01), and heat wind-up (r = 0.66, P < 0.05). Activity-avoidance beliefs correlated with a lower peak VO2 on the cycle test (r = -0.52, P < 0.05), a shorter distance on the 6MWT (r = -0.56, P < 0.05), and more severe self-reported pain (r = 0.61, P < 0.05), reflecting that patients with activity-avoidance beliefs were less physically fit and experienced more severe pain.
The results demonstrate some associations between physical fitness and pain in fibromyalgia and point to the importance of activity avoidance. Although the causal directionality of the associations needs substantiation in clinical research, the findings support the notion that low fitness and activity-avoidance beliefs should be targeted while treating pain in fibromyalgia.