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

Abstract

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.

Figure 1

Brain regions showing significant associations between self-reported physical activity and responses to heat pain in FM patients. A negative correlation was found in the post-central gyrus, extending into the superior parietal cortex (image 1). Positive correlations were found in the left and right dorsolateral prefrontal cortex (image 2), posterior cingulate cortex (image 3), and the mid to posterior insula (image 4). Images shown are with voxel-wise threshold set a p=0.005 and cluster size thresholding at 200 mm³. Functional timeseries data (average cluster values) for each individual were extracted and are shown plotted against physical activity values with the corresponding r-squared values.

Figure 2

A significant negative correlation between accelerometer counts per minute and responses to heat pain in FM patients was found in the superior frontal cortex/frontal pole (images 1 and 2). Images shown are with voxel-wise threshold set a p=0.005 and cluster size thresholding at 200 mm³. Functional timeseries data (average cluster values) for each individual were extracted and are shown plotted against physical activity values with the corresponding r-squared values.

Figure 3

Brain regions showing significant associations between average accelerometer counts per minute of wear time and responses to heat pain in healthy controls.Positive correlations were found in the mid anterior and posterior cingulate cortices (image 1), a region in the lateral prefrontal cortex (image 2), the superior temporal cortex (image 3) and the posterior insular coretx (image 3). Images shown are with voxel-wise threshold set a p=0.005 and cluster size thresholding at 200 mm³. Functional timeseries data (average cluster values) for each individual were extracted and are shown plotted against physical activity values with the corresponding r-squared values.