I always thought the runner’s high was the body’s way of communicating approval. A reward for pushing it, taxing it in a controlled way.

But what causes that amazing, drug-free high when we run, walk or engage in certain physical activities? Or, to rephrase the question, what’s the easiest, surest way of getting that natural high on demand?

Endorphins. That’s the stock answer you’ll get from most personal trainers when you ask them what causes that tripped out Zen master vibe. And who’s to blame ‘em? Science still hasn’t figured out what exactly the runner’s high is and what causes it.

Other, more fringe answers range from “it’s your body going into shock as you pound your knee joints into powder” to hormonal secretions from the brain.

Another guess might be a growth hormone response. A recent and most plausible explanation is likely bio- substances in the brain, called neurotransmitters. Dopamine, serotonin and norepinephrine are all feel good neurochemicals that start flowing when the legs get going.

So what’s the secret to getting the runner’s high? The answer seems to be brisk, repetitious movement for at least 30 minutes.

That’s it.

You don’t have to pound the pavement in your Asics.You can feel bliss simply by walking or even working — as long as it meets those simple requirements.