Dr. Ross Tucker answers:
The endorphins are a big part of it.
For the non-running-high readers among us, endorphins are chemicals released in our brains when we perform physical exercise, and are remarkably similar to morphine in structure. They reduce pain, and create that feeling of euphoria we experience. Well, some of us do; I’ve seen studies reporting that anything from 30 to 70% of runners get this benefit – which means the other 30 to 70% don’t, and probably wonder what the fuss is about.
The intensity of the run makes a difference, because ‘too easy’ doesn’t produce the response, and ‘too hard’ may overwhelm it with exertion. When you find that optimal rhythm and pace, where you’re working hard but not pushing beyond tolerable, that’s where the effect is likely to be largest and most noticeable.
It is also psychological and emotional, because having chosen to run, and then experiencing it, there’s a satisfied feeling that may have a physiological explana-tion, but which boils down to being rewarded for your efforts. I dare say looking into how the neurotransmitters in the brain are changed as a result of this whole ‘reward’ pathway would help explain why so many people get addicted to running – they have to run, or they get grumpy. This too is physiological.
But the emotion and joy of running is perhaps left ‘unphysiological’, and enjoyed for what it is. When running, you’re getting a healthy ‘drug’ whose effects may fade in the short-term; but the benefit doesn’t.