Why does the perceived intensity of chronic pain often decrease when a person engages in moderate exercise, even if the original nociceptive stimulus remains?

💡 Explanation

Moderate exercise activates the descending pain modulation pathway, where periaqueductal gray (PAG) neurons trigger the release of enkephalins. These enkephalins activate inhibitory interneurons in the spinal cord, reducing nociceptive signal transmission; therefore, perceived pain decreases due to this gate control mechanism, rather than inflammation reduction or substance P depletion.

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