K.M. Crombie, A.G. Brellenthin, C.J. Hillard, and K.F. Koltyn.
Pain Medicine 2018; 19:118-123
It is well known that exercise reduces pain in a process called hypoalgesia. For years, it was thought that this was primarily mediated through the body’s internal (endogenous) opioid system. Non-opioid systems are also known to be involved, but these have been poorly understood. The endocannabinoid system (a non-opioid system) is known to modulate pain and might be involved in the hypoalgesia associated with exercise.
This study investigated how exercises reduce pain and how the opioid and endocannabinoid systems interact in exercise-induced hypoalgesia.
Who was it?
There were 58 healthy men and women (average age 21 years). Subjects were not trained athletes.
What was done?
This was a randomized controlled trial involving both pain and exercise protocols. All subjects had blood drawn at baseline and then were given either naltrexone, a drug that blocks the opioid system, or placebo. They rested for 55 minutes and then did pain testing followed by a second blood draw. Next, they completed 3 minutes of isometric exercise at 25% maximal capacity followed by a third blood draw. Lastly, pain testing was done a second time. Levels of five endocannabinoids (AEA, 2-AG, 2-OG, OEA, PEA) in the blood were measured.
Pain was reduced following exercise in both the placebo and naltrexone groups, which suggests that it is mainly the endocannabinoid system (rather than the opioid system) that mediates the pain reduction. Results also suggested that the opioid and endocannabinoid systems interact to influence levels of endocannabinoids.
This study builds on our understanding of the endocannabinoid system as one of the primary mediators of pain, including pain reduction following exercise. Exercise is an easy way to boost endocannabinoid system function and yields many benefits. Exercise can also be combined with other ECS system boosters, such as consumption of CBD, to further reduce pain.