Runner's High and Evolution

After being at home for a little over a week, I'm back in Ann Arbor and have just started my summer research project on neuronal degeneration. Hopefully I can find some way to tie evolutionary or nutritional studies into my research. But since I'm back in Ann Arbor, I thought I would talk about getting high.....off of running. Every athlete doing some kind of aerobic training has felt it. It's that great feeling of accomplishment and relaxation you get after a long run, and it repeatedly motivates you to hit the pavement or trail.

This elevated feeling is due to endogenously produced cannabinoids, which are chemically similar to the molecule THC which is the active component in marijuana. These molecules act on cannabinoid receptors in the central nervous system, leading to a decrease in the perception of pain, regulation of the stress response, and a change in a number of other cognitive effects. In other words, sustained aerobic activity leads to the production of natural pain suppressants that act in a similar manner to marijuana. 

This has been proposed to have EVOLUTIONARY significance because it would have encouraged early mammals, including humans, to run long distances. Running, as we know, promotes increased aerobic performance by increasing stroke volume and improving the efficiency of oxygen metabolism. In addition, running increases bone density and increasing neuronal proliferation. Some research even suggest that humans were built to be long distance runners because of the way our feet and joints are constructed, but that's a topic for another day. Because of all of its positive effects, running may have increased the reproductive success, and therefore getting a runner's high would have been evolutionary beneficial.  

Any triathlete will tell you that the term "runner's high" should be expanded because you get this feeling after practically any type of endurance workout. It helps keep you motivated and push through pain day in and day out, even when training gets rough. Unfortunately, when injury results as a product of overtraining, the lack of endocannabinoids can lead to a feeling of depression and stress. But don't worry, anaerobic exercise also produces that great feeling. So when injured and feeling down, take a break from the cardio and do some resistance or strength training to brighten your day.

Next time your training calls for a LSD (long slow distance) run, remember the powerful effects of enocannabinoids.