Voluntary Chronic Exercise Decreases Nociceptive Responses Before and After a Traumatic Stressor

Abstract

Objective: The hypoalgesic effect of acute bouts of exercise on healthy participants has been well documented across a variety of exercise modalities. However, the effects of a long-term exercise regimen on nociception is fairly unknown. Furthermore, it is unclear if exercise can be an effective treatment for disorders such as posttraumatic stress disorder, which can be characterized by hyperalgesia. The purpose of the current study is to investigate the effects of chronic exercise on thermal nociception before and after a traumatic stressor.

Methods: Twenty-four C57/B6 mice were separated into two groups with 12 animals performing voluntary wheel running over a 5 week period. All mice were assessed weekly to determine the effects of chronic exercise or rest on thermal nociception. After 4 weeks, animals were further divided into 4 groups according to exercise and traumatic stress exposure. All mice were exposed to a 15 minute predator odor paradigm with “no stress” animals being exposed to ambient air and “stress” animals exposed to bobcat urine. All mice were tested 48 hours post exposure for changes in thermal nociception.

Results: Findings from this study yield support that chronic, voluntary exercise decreases thermal nociception in mice over a 4-week period before a traumatic stressor and 48 hours after exposure to the stressor.

Conclusion: In conclusion, voluntary, long-term exercise has been shown to elevate nociceptive thresholds, providing support for these exercise programs in the treatment of stress-induced hyperalgesia.