|Year : 2015 | Volume
| Issue : 3 | Page : 207-209
Runner's high: A review of the plausible mechanisms underlying exercise-induced ecstasy
Sharat Gupta1, Shallu Mittal2
1 Department of Physiology, Gian Sagar Medical College, Rajpura, Punjab, India
2 Department of Physiology, Govt. Medical College, Patiala, Punjab, India
|Date of Web Publication||2-Sep-2015|
House No. 849, SST Nagar, Rajpura Road, Patiala - 147 001, Punjab
Runners high refer to the feeling of exaltation that is experienced by some people who are engaged in strenuous exercise. Until the date, the exact mechanisms underlying this unique mental state continue to be a matter of debate, mainly due to a lack of credible evidence in support of the same. There are many sceptics who dismiss the very notion of runners high because they consider it to be nothing but a mere confabulatory act, which stems from the sense of achievement felt upon successful completion of a physical activity. However, some recent studies have put forth two different mechanisms to explain the exact cause behind this intriguing human emotion. The first and perhaps the most widely accepted notion is related to the exercise-induced endorphin release in the brain, while the second theory proposes the presence of an endocannabinoid system within the human brain, which releases special neurotransmitters during vigorous physical activity. Through this review, we have tried to put together the nitty-gritty of both these theories, with the hope of instigating further research in this hitherto unexplored field.
دراسة استعراضية لليات الذهنية التى تدفع إلى النشوة المصاحبة للمجهود البدنى
النشوة الرياضية (Runner's high) ترمز الى الإحساس العارم والنشوة لدى بعض ممارسى الرياضات المجهدة وإلى اليوم لم يتم التعرف على الالية المحددة التي تسبب هذه الحاله الذهنية الفريدة والتيما زالت مثار الجدل وتحديداً بسبب عدم توفر الادلة الدامغة التى تدعمها . هنالك العديد من الاراء لا تقبل ترفض وجود هذه الظاهرة لدى العدائين وذلك لاعتقادهم انها ليست سوى القليل من اللهو الناتج من الشعور بالإنجاز الذى يعقب النجاح فى النشاط الرياضي، وعلى الرغم من أن بعض الدراسات الحديثة قدمت آليتين مختلفين لتفسير هذا الاحساس الزائف . السبب الاول والذى يحتمل أن يكون اكثر شيوعاً وقبولاً هو أن التمارين تزيد من أفراز هرمون الاندروفين في المخ، بينما السبب الثاني هي نظرية تقول ان وجود نظام endocannabinoid في العقل البشري والذي تفرزه ناقلات عصبية في اثناء التمارين الرياضية المجهدة. ومن خلال هذه المراجعات نجد أننا قد حاولنا أن نجمع خلاصة النظريتين على أمل أن يؤدي ذلك إلى تحفيز إجراء المزيد من الأبحاث لدراسة هذا المجال الغير مطروق.
Keywords: Anandamide, endocannabinoids, endorphins, euphoria, exercise, runners high
|How to cite this article:|
Gupta S, Mittal S. Runner's high: A review of the plausible mechanisms underlying exercise-induced ecstasy. Saudi J Sports Med 2015;15:207-9
|How to cite this URL:|
Gupta S, Mittal S. Runner's high: A review of the plausible mechanisms underlying exercise-induced ecstasy. Saudi J Sports Med [serial online] 2015 [cited 2019 May 21];15:207-9. Available from: http://www.sjosm.org/text.asp?2015/15/3/207/164265
| Introduction|| |
The runners high: Every athlete has heard about it, many believe in it and some even claim to have actually experienced it. The term runners high are used to describe a euphoric state which is experienced by anyone engaged in strenuous exercise.  This phenomenon was first reported in a group of long distance marathon runners who reported that they felt so good after the event as if they had taken some psychedelic drug. However, similar feelings were later reported even in pugilists, rugby players, bikers, grapplers, etc.  Thus, the term runners high is a misnomer, since running is not the only way to get the "high," it can also occur, with other forms of endurance exercises.
It has also been observed by some researchers that this pain numbing euphoria is infrequent, not always reproduced, thus making its occurrence very difficult to study in an experimental setting.  Furthermore, there is a great variation with regards to the description of runners high feeling, since quite a few runners have actually described it as more of a feeling of relaxation, rather than an actual euphoric state, per se. 
Being such a rare and elusive phenomenon, sports scientists have mostly a reserved judgment on the exact mechanisms underlying this unique emotion. At present, two hypotheses, that is, the endorphin hypothesis and the endocannabinoid (eCB) hypothesis are being used to explain the "high" associated with exercise. 
This review is an attempt to present a brief insight into the nitty-gritty of both these mechanisms, so as to update the knowledge of the sports scientists and to encourage further research into this yet unexplored domain.
| Runners High: Evolutionary Perspectives|| |
Some anthropologists believe that runners high is an evolutionary trait that facilitated the survival of early humans in a hostile environment, since the chemicals released during physical activity had the ability to numb pain. Thus, the early humans were able to cover vast distances while hunting or scouring for food.  Some of the existing African tribes make use of a runners high while conducting "persistence hunting." This is a method in which an animal is chased for many miles, until it eventually gets totally exhausted, thereby enhancing its vulnerability of being hunted down. 
| Runners High: Possible Mechanisms|| |
The endorphin hypothesis
This is one of the most popular mechanisms which are commonly cited to explain runners high. It involves the involvement of an opioidergic mechanism in the brain. During periods of intense physical activity, the pituitary gland and hypothalamus release special chemicals called endorphins. The latter mimic the effects of morphine, thereby acting as natural pain killer chemicals. Thus, whenever high amounts of endorphins are released in the brain, it leads to masking of pain and sense of euphoria and well-being. Thus, the endorphin activity can make the physical stress associated with exercise more pleasurable or even addictive. 
Until now, the opioid hypothesis was based entirely on the findings of enhanced endorphin levels in peripheral blood. ,,, However, a credible support to the above hypothesis was lent by the findings of a recent study conducted by a group of German researchers.  This study not only established the relationship of a central opioidergic neurotransmission to perceived euphoria during strenuous exercise, but also disclosed the region-specific changes in opioid binding after exercise. This study was based on the positron emission tomography scan based ligand activation, using a nonselective opioid ligand. A total of 10 athletes were chosen for the study. These athletes were scanned in a random manner on two separate occasions, once at rest and thereafter after 2 h of endurance running (mean distance 21.5 ± 4.7 km). The perceived level of euphoria was estimated using a visual analogue scale (VAS).
Specifically, the euphoria levels were inversely correlated with the binding of nonspecific opioid ligand in the prefrontal/orbitofrontral cerebral cortices, anterior cingulated cortex and insular and parainsular cortex; that is, the regions of the brain involved in emotional processing. This shows that very little opioidergic receptors were available in the above cortical regions, for binding with the nonspecific ligand, since most of the receptors had already been occupied by the endogenous opioids released during endurance running.
Furthermore, in the above participants, while the preexercise VAS euphoria ratings were not significantly different compared with the VAS euphoria ratings taken on a resting day (37.6 ± 19.6 vs. 28.5 ± 17.4, respectively), however the postexercise VAS euphoria ratings were significantly higher (73.3 ± 13.2) as compared to those taken just prior to exercise (37.6 ± 19.6). These findings established beyond doubt, the correlation of endogenous opioid release with the euphoric feeling reported by athletes.
The endocannabinoid hypothesis
For the past several years, runners high phenomenon has been attributed to the release of endorphins, but many recent experimental studies are increasingly favoring the role of a separate mechanism, which includes the release of chemicals known as eCBs, in explaining the genesis of runners high. , They are the endogenous chemicals that originate in the brain, whose activity resembles that of delta-9-tetrahydrocannabinol, which is the primary psychoactive ingredient in marijunana (or cannabis), thus explaining the origin of their name. 
The experimental proof for the eCB signaling system in the brain comes from a recent study led by Prof. Raichlen.  In this study, a group of ten healthy individuals were engaged in 30 min of high intensity treadmill running, at an average of 72% of the maximal heart rate, while another "control" group of eight subjects walked at about half the pace, that is, 44% of the maximal heart rate. In both these groups, the circulating levels of anandamide (AEA) and 2-arachidonoylglycerol (2AG), the key components of eCB signaling system, were estimated before and after exercise sessions, along with a psychological well-being assessment. It was observed that in the first group, there was a significant rise in the circulating levels of AEA and 2AG levels postexercise, along with a self-reported sense of increased well-being. However, among the second group (i.e., controls), there was not much change in the pre- and post-exercise levels of AEA and 2AG.
Even though this study was limited by a small number of runners and the fact that eCB were measured in the bloodstream, yet it helped in establishing a robust correlation between eCB and the "positive affect" changes in the nervous system, since the eCBs are known to easily cross the blood brain barrier. The fact that there was not much change in the pre- and post-exercise circulating levels of AEA and 2AG of the second group, led to the proposal that there was a threshold intensity for triggering eCB signaling and their resultant affective rewards, and also that eCB and endorphins work together in high-intensity exercise only.
| Runners High: Emerging Beliefs|| |
Although the endorphin and eCB signaling hypotheses have provided much insight into the neurobiological mechanisms inducing the "high," yet the exact mechanisms underlying this ecstatic feeling are still a matter of considerable debate. This is because of the notion of many other researchers that a variety of other chemicals such as epinephrine, serotonin, and dopamine are equally important in inducing the "high," as endorphins and eCBs. ,
| Conclusion|| |
Runners high are an intriguing phenomenon that has been frequently reported, yet poorly understood. Further elucidation of the exact mechanisms contributing to the "high" is important, as it may lead to the discovery of a novel therapeutic regimen that may prove useful in the treatment of patients who are suffering from chronic intractable pain, which is refractory to conventional treatment.
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