Monica Shaw

Endorphins: Why runners are on a high

The Daily Telegraph - April 08, 2008

Those struggling to complete the London Marathon this weekend will give thanks to the phenomenon known as "runner's high" - the blissful flood of chemicals that keeps spirits up and prevents the brain from registering pain.

Now a new study demonstrates exactly how this feeling of euphoria caused by endorphins, naturally occurring chemicals, can be used to treat those suffering from chronic pain.

The cause of runner's high has long been debated by scientists and athletes. The most common theory is that endorphins are released during running and interact with sites in the brain called receptors where opiates act to elevate the runner's mood.

But due to the limitations of the technology, scientists were only ever able to show that running released endorphins in the blood, not that this increase was registered by the brain.

Now, however, researchers in Germany have used positron emission tomography (PET) scans to visualise endorphins in the brain. As they report in the journal Cerebral Cortex, the team examined the brains of 10 volunteers before and after a two-hour run.

Before the scan each subject was injected with a radioactive tracer that competes with endorphins to bind to the opiate receptors. The PET scan detected the tracers and projected the distribution on to a three-dimensional image of the brain.

"The tracer and the endorphins are in direct competition for opiate receptors," explains Prof Henning Boecker, who co-ordinated the study at the University of Bonn. "The more endorphins in the brain, the less tracer binding we see."

By comparing the pre- and post-run scans, Boecker showed that "the reduction in opiate binding [after the run] was highly significant, not in random areas but focused in the prefrontal and limbic regions, areas which we know to be involved in emotional processing".

These same areas also cause the "shivers" people experience when listening to music they find particularly moving.

The runners, who were not told that the study was focused on endorphins and runner's high, were also asked about their moods, and reported a significant increase in euphoria after the run that correlated with the release of endorphins.

While the research confirms the link between endorphins and runner's high, it also shows that athletes experience the high in different ways. Some feel "calm" while others report "extreme euphoria". Jurg van der Walt, an experienced marathon runner, says it is a "heightened sense of awareness", while Stuart Holliday, currently training for his first London Marathon, says it makes him feel "elated".

But as well as confirming what was already suspected, the study could also have important implications for non-runners.

Endorphins are already known to help the body manage pain, and other studies have shown higher pain tolerance in marathon runners than non-runners - so triggering their release could help those experiencing pain to manage their conditions.

"Endorphins are released in areas of the brain that are centres of pain suppression," says Prof Thomas Tölle, a co-author of the study. "Now we hope that these images will impress our pain patients and motivate them to take up sports training within their available limits."

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