J Appl Physiol. 2012 Dec 27. [Epub ahead of print]
Regular physical activity prevents development of chronic pain and activation of central neurons.
Source
1The University of Iowa.
Abstract
Chronic musculoskeletal pain is a significant health problem and is associated with increases in pain during acute physical activity. Regular physicalactivity is protective against many chronic diseases; however it is unknown if it plays a role in development of chronic pain. The current study inducedphysical activity by placing running wheels in home cages of mice for 5 days or 8 weeks and compared these to sedentary mice without running wheels in their home cages. Chronic muscle pain was induced by repeated intramuscular injection of pH 4.0 saline. Exercise induced pain was induced by combining a 2h fatiguing exercise task with an low dose muscle inflammation (0.03% carrageenan), and acute muscle inflammation was induced by 3% carrageenan. We tested the responses of the paw (response frequency) and muscle (withdrawal threshold) to nociceptive stimuli. Since the RVM is involved in exercise-induced analgesia and chronic muscle pain, we tested for changes in phosphorylation of the NR1 subunit of the NMDA receptor in the RVM. We demonstrate that regular physical activity prevents the development of chronic muscle pain and exercise-induced muscle pain by reducing phosphorylation of the NR1 subunit of the NMDA receptor in the central nervous system. However, regular physical activity has no effect on development of acute pain. Thus, physical inactivity is a risk factor for development of chronic pain and may set the nervous system to respond in an exaggerated way to low-intensity muscle insults.
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