The relationship between physical activity and brain responses to pain in fibromyalgia.

UNLABELLED: The relationship between physical activity and central nervous system mechanisms of pain in fibromyalgia (FM) is unknown. This study determined whether physical activity was predictive of brain responses to experimental pain in FM using functional magnetic resonance imaging (fMRI). Thirty-four participants (n = 16 FM; n = 18 Control) completed self-report and accelerometer measures of physical activity and underwent fMRI of painful heat stimuli. In FM patients, positive relationships (P < .005) between physical activity and brain responses to pain were observed in the dorsolateral prefrontal cortex, posterior cingulate cortex, and the posterior insula, regions implicated in pain regulation. Negative relationships (P < .005) were found for the primary sensory and superior parietal cortices, regions implicated in the sensory aspects of pain. Greater physical activity was significantly (P < .05) associated with decreased pain ratings to repeated heat stimuli for FM patients. A similar nonsignificant trend was observed in controls. In addition, brain responses to pain were significantly (P < .005) different between FM patients categorized as low active and those categorized as high active. In controls, positive relationships (P < .005) were observed in the lateral prefrontal, anterior cingulate, and superior temporal cortices and the posterior insula. Our results suggest an association between measures of physical activity and central nervous system processing of pain. PERSPECTIVE: Our data suggest that brain responses to pain represent a dynamic process where perception and modulation co-occur and that physical activity plays a role in balancing these processes. Physically active FM patients appear to maintain their ability to modulate pain while those who are less active do not.