Friday, 18 February 2011

What happens to your brain during runners high?

In my last post, I was suggesting runners high could be a motivating factor in maintaining training and have a role in improving performance. If exercise feels good, it follows you may be more likely to continue at your endeavours as the happy feeling rewards the effort put in. Todays post will try and explain what is actually happening in your brain when you experience runners high, how this affects pain management and the implication for 'addiction' to exercise.

In the previous post I explained how research had demonstrated an endorphin driven runners high. Endorphins are the molecules produced in the pituitary gland and the hypothalamus that act as the bodies 'homemade' opiates. These act to relieve pain and produce a feeling of calm and well being. Endorphins are also produced and provide the feelings experienced when we eat spicy food, fall in love or have an orgasm.

The endorphin hypothesis for runners high holds that when strenuous exercise takes a person over a physical threshold, endorphin production is activated. Endorphins are released during long, continuous workouts, when the level of intensity is between moderate and high, and breathing is difficult. During a release of endorphins the person may be exposed to bodily harm from strenuous exercise after going past their body's physical limit. With runners this means that they can keep running despite pain, surpassing what they once considered to be their limit, in turn experiencing the phenomenon as pleasurable. It also goes someway to accounting for the crazy look in the eyes of runners and their behaviour after a heavy workout!

Boecker's research in 2008 showed for the first time that an increase in the release of endorphins occurred in certain parts of the athletes' brains after conducting scans of runners 2 hours after exercise (compared to their resting state beforehand). Boecker's findings showed that endogenous opiod neurotransmitters are released in the frontolimbic system of the brain. Thus more of the bodies own opiods were released in runners in the study, who also reported a significant increase in euphoria and happiness ratings compared to their resting state.

However, it is also suggested by researchers that endorphins are just some of the many chemicals that contribute to runner's high. Other candidates include epinephrine, serotonin, and dopamine. Yesterday, whilst researching this subject I found evidence cited in the New York Times proposing that the endocannabinoid system may be more responsible for runners high than endorphins.

The main thrust of this argument is that endorphins, are composed of relatively large molecules, “which are unable to pass the blood-brain barrier,” (Hill, 2011 in the article here). This contradicts Boecker's findings, and according to Dietrich and McDaniel (2004) “several prominent endorphin researchers have criticised the endorphin hypothesis for being “overly simplistic” and “poorly supported,” though it should be noted these views were made before Boecker's study. Instead, the endocannabinoid system, is proposed by researchers such as Hill as being more responsible for runners high as these molecules produced naturally by the body are small enough to be able to cross the brain blood barrier and thus account for the “unexpected psychological changes, such as euphoric sensation, a heightened sense of well being and a transcendence of space and time.” These are the same sensations experienced in the brain when people take marijuana, as the drugs active ingredient also binds to the same receptors.

Authors behind the endocannibinoid hypothesis for runners high (such as Dietrich and McDaniel) don't claim that their theory is 100% sound, and want researchers from a variety of backgrounds to investigate further. One criticism that can be levelled at a lot of the research is that it relies on findings from research on rats, and we cannot directly take results from such studies and apply them to humans. However, Dietrich and McDaniel, and another study by Dietrich in 2003 was researched on humans to go some way to prove the cannibinoid hypothesis.

I've emailed Dr Boecker to try and see if he is able to respond to the evidence presented by the New York times article and studies proposing the cannibinoid hypothesis. If he is willing to provide a view for the blog then I'll include this. As is, I think this is a fascinating area that has a long way to run (if you'll pardon the pun) in accounting for how as a species we subjectively experience elation and pain management in relation to endurance exercise. It may also go some way to account for what some people would term 'exercise addiction' and overtraining. In one of my next blogs, my colleague Andy Preston of UEL will write more on psychological coping strategies related to marathon running. As ever, please feel free to comment and feedback on the information I've given you here.


oliverslay said...

are you sure that the 2004 study contradicts Boecker's findings?

Boecker's study - is talking about endogenous opioid neurotransmitters released in the frontolimbic system of the brain... and not about hormone endorphins released into the blood in the pituitary gland...


Stu Holliday said...

Not sure Oli! I don't claim to be a fully fledged neuroscientist by a LONG stretch! which is why I've opened this up to comments such as yours and (hopefully) a response from Boecker himself.