Michael Mosley

Is runner’s high a real thing?

Spring is the time when fair-weather runners like me pull our trainers out of hibernation, dust them down and reluctantly start running again. I say ‘reluctantly’ because I don’t enjoy running. I do it because I realise it is good for my lungs, my heart and my brain. I also do it because I am worried that soon I won’t be able to keep up with my wife. But I don’t, at any point, get pleasure from it. I certainly don’t experience the intense pleasure that many avid runners describe as ‘runner’s high’.

I was curious about what was going on, so as part of a recent programme for BBC One, The Truth About Getting Fit, I decided to find out more.

For a long time, the positive feelings that runners describe has been put down to endorphins. These are peptides that our bodies produce which activate opioid receptors in the brain. But physiologist Dr Saoirse O’Sullivan believes a different brain signal may be responsible: a class of chemicals called endocannabinoids. These molecules are neurotransmitters that are similar in structure to the main chemical in cannabis. They bind to cannabinoid receptors throughout the body, including the brain.

To see if endocannabinoids really do rise in the blood of running enthusiasts, we asked O’Sullivan to help us do an experiment which, as far as we could find out, had never been done before. We got a small group of enthusiasts to go for a short run, only half an hour, outdoors. Previous experiments have involved much longer runs in a lab setting.

So what did we find? Well, once their blood was analysed it was clear that even a short run had had a striking effect. “When you came back from the run, you had, on average, 30 per cent more endocannabinoids in your blood than you did before you set off,” O’Sullivan told our volunteers. “So that exercise, short though it was, really does seem to have led to a big increase in endocannabinoids.”

One of our runners, a woman who suffers from severe bouts of depression, had a particularly marked response. She is aware of the profound effect running has on her mood and has been using it as a form of selfmedication for some years now. She is a keen marathon runner and is now progressing to running ultra marathons.

So even a short, easy run can bring some people a naturally produced chemical high. But why do we have this system at all? O’Sullivan believes the release of endocannabinoids may be a way for our bodies to encourage us to keep fit. “We know that we’re mentally and physically healthier when we exercise. So the body having an immediate reward system for exercise would seem like a good evolutionary thing,” she says.

That still doesn’t explain why some people get a runner’s high while others don’t. The next step would be to take a group of people who don’t enjoy running, like me, make us run and see what effect, if any, that has on our endocannabinoid levels. It could be we don’t produce as much, it could be we don’t have such sensitive receptors, or it could be we don’t push ourselves hard. I’m up for finding out. Any other exercise sloths care to join me?