Of all the neurotransmitters dopamine has long fascinated me the most. I know that sentence doesn’t seem like we’re going anywhere exciting but we are. Let’s start with the spoiler that if you like exercising and racing dopamine likely plays a huge part in that. Dopamine fascinates me because it is the reward we get for working hard, learning and accomplishing something in the long term. More evolutionarily minded people than me sometimes give dopamine the credit for a lot of what humans have accomplished. But the flip side of that coin is its huge role in addiction. If someone is struggling with an addiction it’s largely dopamine’s fault. How can something be so good and so bad for our lives at the same time? Dopamine has a role in exercise as well but you’re probably more familiar with the roles of serotonin and adrenaline. I’ve long wondered if it’s part of what keeps us coming back to working out and why the odd person takes exercise too far. So let’s dive into the scientific literature on the subject and find out together.
What is dopamine
Dopamine is both a hormone and a neurotransmitter which is the role we’ll mostly be focusing on today. Which is to say it works on the body and in the brain. Dopamine is involved in reward motivated behavior. In other words dopamine is released and makes you feel good as you work towards a goal that is hard. That dopamine rush or lack there of propels your behavior towards or away from achieving that goal. In some ways its responsible for the good feelings you have while cooking a meal before you eat it, studying for a test before you get the A and doing yet another training run before the big race. Parkinson’s disease is characterized by a lack of dopamine secretion within the brain and it is thought to have a role in several other disorders as well.
Dopamine and Learning
Dopamine also has a role in learning. It’s the little reward that bridges the gaps in progress. Have you ever developed a new skill? Well dopamine is what neurologically got you there. Let’s take my learning to split wood as a simple example. When I started it wasn’t pretty I lacked the strength, aim and basic knowledge to know how to do it. It would literally take me about 80 impacts to split a frozen log a single time. Here’s a video honey took of me secretly around that time. But there were little successes along the way too. Each blow that moved the axe head was a small success, the first visible cracks forming in the log, the fact that I was halfway to the bottom and eventually the log finally split in half. Each split took me about 10 minuets. By the end of that long winter I got stronger and my aim improved (slightly) and that first blow stood the axe in the log a few dozen more blows with the sludge hammer and they were splitting every three minuets or so. Now a couple of years on I can split a chord with an axe in about 4 hours (not all at once) and sometimes the log splits on the very first blow. Dopamine is what kept me going between all those little rewards and through the many, many times I got the axe stuck in a piece of wood. Over the span of one winter I improved drastically after a couple of winters its no big deal really if the splitter is broken I can split what we need for the week in about an hour and I have a legit life and survival skill I didn’t before. Thank you dopamine!
Dopamine and addiction
I think the general public probably knows the most about dopamine’s role in addiction if anything. Virtually every addictive drug out there increases dopamine secretion or lowers re-uptake meaning that you have more of it available than you really should. We are ‘programed’ if you will, to work for that dopamine reward and that is thought to be responsible for the addictive nature of these drugs and the lengths people will go to get them. As one wise person I know said “hard drugs don’t cost that much because you aren’t going to want more.” That wanting largely comes from dopamine. Dopamine normally reinforces that a certain behavior is a good one when the rush comes naturally so you can see why dopamine also has a major role in making your ‘think’ taking more drugs is a perfectly reasonable thing to do. It’s supposed to make you think “that run was pretty good, I think I’ll go for another one tomorrow” not “that was great, sure I’ll do another line.”
So all that got me thinking what about dopamine and exercise? Why do we keep running, lifting and whatever else since the rewards are pretty few and far between? Why do a few people seem to literally get addicted to exercise? Could dopamine be responsible for these things and making some crazy people do things like ultras and ironmans? Seems like it could be a thing right? Since it’s a field that’s totally unrelated to stress hormones my PhD didn’t really answer these questions for me but now that I have the time let’s look into this together?
Dopamine and exercise
First of all what happens to our dopamine levels when we do exercise? The short answer is that exercise does increase the level of dopamine in the brain. So when you exercise regularly you produce more dopamine like all of the time, even when you’re totally rested. You produce even more when you are actually exercising though too. You do however produce slightly fewer receptors to dopamine meaning less of it interacts with ‘target’ cells. But… the dopamine you produce doesn’t get recycled as fast meaning it interacts with the receptors you do have for a longer time. Overall well trained people and those that have just worked even those that just worked out once do have more dopamine available to them. So yes exercise does boost dopamine levels before, during and after exercise in trained individuals all the time and untrained individuals when they work out (Lin and Kuo, 2013). But there are other roles for dopamine too.
Dopamine and fatigue
There is very strong evidence that dopamine has a role in endurance. When you exercise, and do almost any exercise by the way, dopamine levels increase. But right around the time you ‘hit the wall’ or become exhausted and can’t continue dopamine levels have returned to normal. This has been proven in many, many animal studies and now a few human studies as well. Since endurance training makes athletes able to perform at a high level for longer and longer periods of time researchers hypothesized that this return to baseline levels of dopamine occurs later in trained versus untrained individuals and that turns out to be true too (reviewed in Foley and Fleshner, 2008). This reveals a role for dopamine in changes in central fatigue. Central fatigue is the tiredness that comes not from your muscles that you’re actually using to perform an activity. Even though your muscles might not actually be totally depleted you lose motivation and decrease your level of performance. So as you train longer and longer you put off the point of dopamine depletion a little bit later with specialized endurance training. Sounds a lot like mile 20 of a marathon right?
Dopamine and habitual exercise
Do you ever notice that people who run, cycle, swim, do yoga or whatever do it like all the time? Well it turns out that dopamine may have a role in that as well. Let’s take a slight detour back into the world of addiction though first. Interestingly each time after the first time we receive a biological stimuli like food or exercise we undergo a process called habituation. We either produce a little less dopamine or it effects us a little less. This may make us strive to take on new challenges or maybe try new foods. However when dopamine pathways are stimulated by drugs there is no such habituation, meaning it has the same big effect that it did the first time. In this case we become more like Pavlov’s dog we keep doing the same drug because we get the same reward (Di Chiara and Bassareo, 2007). Over time this changes our learning because we separate the action from the outcome which is normally related. If you want that big first time dopamine rush again you have to accomplish something new, go faster, lift heavier or go further than you ever have before. In drug addicted patients it becomes a habituated response to the drug because the same stimulus always gets the same dopamine reward and learning via this pathway can effectively stop. After all where’s the motivation to do better if you have a dopamine rush coming anyway?
Because exercise stimulates the dopamine pathway in a ‘normal biological’ way doing the exact same thing a second or 50th time doesn’t feel as great. Personally being a few seconds off my 5k PR time doesn’t mean its really any less of an accomplishment or I’m any less fit does it? But… dopamine habituation has occurred and so it doesn’t feel quite as great does it? It’s not to say regular exercisers are ‘chasing’ that initial dopamine high every time they workout. After all they still do get a rush every time they hit the gym. As they train that dopamine hangs around longer and longer. That’s pretty great too and that consistent if slightly lower dopamine rush can be enough to keep us going too. But it likely has a role in why we are often trying to go faster, further or accomplish something we’ve never been able to do before. The potential intensifying rush is what keeps us going, striving and learning on our way to the next record!
Other cool things dopamine does
While I’m reading all sorts of articles on a subject like this I always come across some other cool studies that don’t quite fit in but I still want to share. So in that vein here are some other cool things dopamine does that are pretty cool too:
- It helps you perform at higher temperatures (Watson et al., 2005).
- Dopamine from exercise might make you a better learner after a workout (Eddy et. al., 2020).
Here are my takeaways from all this is the same as people who are more expert in this exact field. Dopamine definitely has a big role in exercise. In getting us out there, in keeping us out there longer and getting us back out there the next day! Dopamine is also what’s pushing us to PR, tackle a harder competition and really just accomplish great things! I didn’t dig deep into the rare cases of exercise addiction and dopamine but based on all this it probably plays a role in that too. Have you learned something today? Did this post have you nodding, agreeing and thinking that explains so much? Leave it in the comments below!
Read what I read:
Di Chiara and Bassareo, 2007. Reward system and addiction: what dopamine does and doesn’t do. Current opinion on pharmacology.
Eddy et al., 2020. Voluntary exercise improves performance of a discrimination task through effects on the striatal dopamine system. Journal of Learning and Memory.
Foley and Fleshner, 2008. Neuroplasticity of Dopamine Circuits After Exercise: Implications for Central Fatigue. Nuromolecular Medicine.
Lin and Kuo, 2013. Exercise Benefits Brain Function: The Monoamine Connection. Brain Science.
Watson et al., 2005. Acute dopamine/noradrenaline reuptake inhibition enhances human exercise performance in warm, but not temperate conditions. Journal of physiology.
Sweat Sweetly 