Runner's high is often described as a feeling of emotional well-being (euphoria, even) that some folks experience during long-distance runs. They become mentally detached from the act of running, achieving a meditation-like state. They relish this high as a completely natural, wholesome reward - and, ultimately, an incentive - for rigorous training. So who WOULDN'T want runner's high?

Elite runners, for one. Most of these athletes work hard to tune into their body's signals and to use those signals to shape their racing strategy during competition. From their viewpoint, the mental detachment of the runner's high would be detrimental to their performance.

This isn't to say that the runner's high is bad. It's just good to have perspective on what works - and doesn't work - for the vast range of us who choose to run.