So This Is Why Rose Trains For and Runs In Marathons

From CNN:

The same family of chemicals that produces a buzz in marijuana smokers may be responsible for "runner's high," the euphoric feeling that some people get when they exercise, U.S. researchers say.

Arne Dietrich, the study's principal investigator and a former visiting professor at Georgia Tech in Atlanta, believes the body releases cannabinoids to help it cope with the prolonged stress and pain of moderate or intense exercise.

He added that the findings could provide sufferers of glaucoma and chronic diseases an alternative to using marijuana for pain control. Use of the drug for medical purposes has been approved by voters in some states, but remains illegal under federal law and highly controversial in the medical community.

So instead of smoking marijuana to relieve pain, you can exercise to the point of even more pain to gain desired pain relief. That's a suggestion that will be well received.