German researchers have confirmed the age-old hypothesis that chemicals naturally released in the brain, called endorphins, are the reason why prolonged jogging raises people's spirits.
A team of experts from the Technische Universitat Munchen and the University of Bonn claims that its imaging study is the first to show an increased release of endorphins in certain areas of the athletes' brains during a two-hour jogging session.
Over time, people have coined the term "runner's high" for the high that accompanies jogging. Though endurance sports have long been seen as reducing stress, relieving anxiety, enhancing mood and decreasing the perception of pain, the cause of such positive effects on the senses remained unclear to date.
Many attributed the positive effects of endurance sports to endorphin release, but had no proof to support their theory.
With a view to confirm the 'Endorphin Hypothesis' in the current study, the research team scanned 10 athletes before and after a two-hour long-distance run with the help of an imaging technique called positron emission tomography (PET).
The researchers used the radioactive substance [18F]diprenorphine ([18F]FDPN), which binds to the opiate receptors in the brain and hence competes with endorphins, in the study.
"The more endorphins are produced in the athlete's brain, the more opiate receptors are blocked," says Professor Henning Boecker, who co-ordinated the research at TUM and is now in charge of the 'Functional Neuroimaging Group' at the Department of Radiology, University Hospital Bonn.
While comparing the images before and after two hours of long distance running, the researchers observed a significantly decreased binding of the [18F]FDPN-ligand, suggesting that the production of endorphin increased as the subjects did long-distance running.
"We could validate for the first time an endorphin driven runner's high and identify the affected brain areas. It's interesting to see that the affected brain areas were preferentially located in prefrontal and limbic brain regions which are known to play a key role in emotional processing. Moreover, we observed a significant increase of the euphoria and happiness ratings compared to the ratings before the running exercise," says Boecker.
Professor Thomas Tolle, head of a research group called 'Functional Imaging of Pain' at TU Munich, adds: "Our evaluations show that the more intensively the high is experienced, the lower the binding of [18F]FDPN was in the PET scan. And this means that the ratings of euphoria and happiness correlated directly with the release of the endorphins."
The researchers say that their findings are relevant even for patients suffering from chronic pain, as endorphins are produced in areas of the brain that are involved in the suppression of pain.
"The fact that the endorphins are also released in areas of the brain that are at the centre of the suppression of pain was not quite unexpected, but even this proof was missing. Now we hope that these images will also impress our pain patients and will motivate them to take up sports training within their available limits," Professor Tolle said.
The results of the study have been published in the journal 'Cerebral Cortex'.