An fMRI study on the acute effects of exercise on pain processing in trained athletes

• Published in: Pain (Amsterdam) Vol. 153; no. 8; pp. 1702 - 1714
• Main Authors: Scheef, Lukas, Jankowski, Jakob, Daamen, Marcel, Weyer, Gunther, Klingenberg, Markus, Renner, Julia, Mueckter, Sara, Schürmann, Britta, Musshoff, Frank, Wagner, Michael, Schild, Hans H., Zimmer, Andreas, Boecker, Henning
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA Elsevier B.V 01.08.2012; Elsevier
• Subjects: Adaptation, Physiological; Adult; Affect; Biological and medical sciences; Brain - physiology; Endorphin; Exercise - physiology; fMRI; Fundamental and applied biological sciences. Psychology; Humans; Illness and personality; Illness, stress and coping; Magnetic Resonance Imaging - methods; Male; Opioid; Pain; Pain Perception - physiology; Pain Threshold - physiology; Periaqueductal gray; Physical Endurance - physiology; Physical exercise; Psychology and medicine; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Running - physiology; Somesthesis and somesthetic pathways (proprioception, exteroception, nociception); interoception; electrolocation. Sensory receptors; Vertebrates: nervous system and sense organs; Physical exercise; fMRI; Periaqueductal gray; Pain; Opioid; Endorphin; Affect; Human; Interaction; Central nervous system; Athlete; Neuropeptide; Opioid peptide; Nuclear magnetic resonance imaging; Encephalon; Locomotion; Walking; Treatment; Cingulate cortex; Periaqueductal gray matter; Perception; Insular cortex; Neurotransmission; Functional imaging
• ISSN: 0304-3959; 1872-6623
• DOI: 10.1016/j.pain.2012.05.008

Endurance exercise modulates affective pain ratings and pain-evoked responses in distinct areas of the human pain matrix, presumably via central opioidergic modulation. Endurance exercise is known to promote sustained antinociceptive effects, and there is evidence that the reduction of pain perception mediated by exercise is driven by central opioidergic neurotransmission. To directly investigate the involved brain areas and the underlying neural mechanisms in humans, thermal heat-pain challenges were applied to 20 athletes during 4 separate functional magnetic resonance imaging (fMRI) scans, i.e., before and after 2hours of running (exercise condition) and walking (control condition), respectively. Imaging revealed a reproducible pattern of distributed pain-related activation in all 4 conditions, including the mesial and lateral pain systems, and the periaqueductal gray (PAG) as a key region of the descending antinociceptive pathway. At the behavioral level, running as compared with walking decreased affective pain ratings. The influence of exercise on pain-related activation was reflected in a significant time×treatment interaction in the PAG, along with similar trends in the pregenual anterior cingulate cortex and the middle insular cortex, where pain-induced activation levels were elevated after walking, but decreased or unchanged after running. Our findings indicate that enhanced reactive recruitment of endogenous antinociceptive mechanisms after aversive repeated pain exposure is attenuated by exercise. The fact that running, but not walking, reproducibly elevated β-endorphin levels in plasma indicates involvement of the opioidergic system in exercise. This may argue for an elevated opioidergic tone in the brain of athletes, mediating antinociceptive mechanisms. Our findings provide the first evidence using functional imaging to support the role of endurance exercise in pain modulation.