A new study is tapping into a phenomenon most of us have heard about and some of us might claim to have experienced at some point – “runner’s high”.
In doing so, this study touches on something fundamentally human.
Put simply, our bodies were made to move. Our predecessors were long-distance endurance runners who could work really hard, from an energy-expenditure perspective, if it was required.
Even now, if we really had to, most of us could exert ourselves at a very high level, significantly increasing our energy expenditure, even if was only for a few seconds.
So why don’t we move more? Why are we facing an obesity epidemic driven largely by sedentary behaviour? How come some people enjoy physical activity more than others?
Runner’s high – or the idea of it – is one of the things that drives some people to exercise – a neurobiological reward that occurs during and after distance running, creating a sense of euphoria for the athlete.
This natural high, say some, provides an improved sense of well-being, reduces anxiety, induces post-exercise calm, and can even reduced pain.
But from a “hard-science” perspective, what is this “high” caused by and does it exist beyond the purely psychological?
There are many eCBs but the one that’s been receiving much attention of late is anandamide (or AEA). Research has shown an increase of AEA in plasma levels after moderate intensity aerobic activity (running or cycling).
Problem solved, right? AEA causes runners high. Slow down, Monoghetti – not so fast. Most of this evidence has been shown in animals other than humans.
Enter David Raichlen and colleagues who wanted to measure plasma levels of eCBs in two “cursorial” (adapted to, or specialised for, running) species – humans and dogs – and one non-cursorial species – ferrets.
In their study, published late last week, all species were made to run and walk on a treadmill for 30 minutes continually. They also had their blood taken before and after each of the trials in order to be analysed for eCBs.
Unfortunately, the ferrets weren’t so keen on treadmill-running so their running trial data was compared with data where ferrets sat quietly in a cage for 30 minutes.
A questionnaire was used to assess the psychological state of the human subjects before and after all trials.
So what happened? Well, Raichlen and colleagues found dogs and humans showed significant increases in plasma levels of AEA following a treadmill run but neither showed any considerable increases in AEA levels after walking trials.
Meanwhile the researchers recorded no change to AEA levels in ferrets during high-intensity exercise.
In other words, humans and dogs experience runner’s high while ferrets have no such feelings.
So now what? Well, despite the study’s acknowledged limitations – the ferrets being uncooperative, for instance – the results here are pretty impressive.
This is the first study to show variation in neurotransmitter signalling following exercise in different species. As such, this study might explain differences in the types of movement and exercise that species find natural.
In humans and dogs, running activated the eCB system, likely leading to an improvement in aerobic exercise performance. This is not the case in ferrets.
The increased levels of AEA in humans (and dogs) confirms the role of eCBs in generating positive psychological effects. As it turns out, there may actually be some substance to “runner’s high”.
So what does this study mean for those of us who are not endurance athletes? How can we experience “runner’s high”? Could this even be the solution to our obesity crisis and help end our sedentary ways?
Well, it turns out one might need to be reasonably fit already before enough eCBs can be produced to evoke the natural “high”.
The suggestion by the authors that exercise could be used as a “drug” to improve our mental state is worth considering, but this needs further investigation.
While this neurobiological underpinning of endurance exercise is significant, it’s important to recognise that one big thing separating animals from humans is our capacity to make informed choices.
We need to make the decision to get off the couch, to go for that run, to get fit. And understanding the motivations and rewards behind those decisions introduces a whole new level of complexity to the discussion.