With the annual London Marathon approaching this weekend, thousands of amateur runners will have discovered the meaning of Runners’ High.

As the body pushes itself through the “first wind” after around 20 minutes of effort, a feeling of euphoria sets in as body chemicals called endophins kick in. These are responsible for blocking pain, but also have a distinctly narcotic effect, which is why some people become totally addicted to workouts and training.

Endorphins are released during sustained effort and affect sites in the brain called receptors where opiates elevate the runner’s mood. Yes, opiates. It really is that powerful.

Non-runners are also affected in a medical sense. People suffering chronic pain can benefit from endorphins too.

Professor Thomas Tolle, who co-authored a study on the subject, says, “Endorphins are released in areas of the brain that are centres of pain suppression. Now we hope [our study] will impress our pain patients and motivate them to take up sports training within their available limits”.

So, run for pain-free health seems to be the message.