P.B. Sparling, A. Giuffrida, D. Piomelli, L. Rosskopf, A. Dietrick
Neuroreport (2003), 14(17): 2209-2211
The endocannabinoid system (ECS) was discovered in the late 1980’s, and the following decade saw the identification of several components of the system. The ECS is widely recognized as the “master regulator” of homeostasis. It is found in all human physiological systems, including the musculoskeletal and nervous systems. It was hypothesized that exercise might activate the ECS, which might explain some of the effects of exercise including pain relief and feelings of well-being.
This was the first study to investigate the ECS and exercise in humans. By measuring levels of the endocannabinoids anandamide and 2-AG before and after exercise, researchers investigated whether exercise activated the ECS.
Who was it?
This study included 24 young males (average age 23.7 years). Subjects were trained athletes.
What was done?
Subjects were randomly divided into three groups: (1) running, (2) cycling, and (3) sedentary (control). For exercising subjects, there was a 5-minute warm up followed by 45 minutes of exercise at 70-80% of their maximum heart rate. Control subjects remained seated for 50 minutes. Blood was taken immediately before and after exercise and levels of the anandamide and 2-AG were measured.
In control subjects, levels of anandamide and 2-AG were statistically unchanged after a 50-minute rest. In exercising subjects, levels of anandamide were statistically increased after exercise, in both the running and cycling group. Levels of 2-AG were increased after exercise, but this did not reach statistical significance.
Follow up studies later showed that the “runner’s high” experienced with exercise is caused by increases in endocannabinoids rather than opioids made in the body. Later studies also showed that gentle exercise such as walking does not have a powerful ECS activating effect, suggesting that more intense exercise is required for this effect. This seminal study showed that both running and cycling at 70-80% of maximal heart rate activates the ECS and that aerobic exercise is an important tool that can be used to increase ECS tone.