Most runners would agree that running makes them feel better. Whether a marathoner, sprinter, or just a recreational jogger, all would say similar things about running: “I feel powerful when I run”, “Running makes me feel strong”, “When I get stressed, I run”. Such statements would attest to the effect exercise has on mood. While it is clear exercise lifts mood, the physiological explanation is not so clear. What affect does exercise really have on the brain? To answer this question, we must know a little bit about how the chemicals in the brain [neurochemicals] affect mood.
There are four main neurochemicals that affect mood. They are: Serotonin, Epinephrine, Dopamine, and Endorphin. Serotonin serves to elevate mood, increase feelings of satiety, and lift depression. We have all experienced a rise in serotonin at some point. It is that satisfied feeling we have after a long run, or a large plate of pasta. It is also that feeling of comfort we get from spending time with close friends, and/or family. Serotonin can become depleted with chronic stress or anxiety, starvation or a low carbohydrate diet, and inactivity, leaving you feeling depressed, irritable, moody,and exhausted. Conversely, serotonin is strongly elevated after a long run, or workout, even at moderate intensity levels. Epinephrine is responsible for the “fight or flight” response that occurs when we get scared, or feel stressed. The effect epinephrine has on the body is to increase heart rate and blood pressure, elevate temperature, stimulate the sympathetic nervous system [used for voluntary muscle contraction], repress the parasympathetic nervous system [used for digestion, immune response, injury repair, and sleeping] and increase cortisol levels. In today’s fast-paced world, we all probably experience epinephrine on a daily basis. Chronically racing to get things done, being late, driving in rush hour traffic, juggling too many tasks at once, and starvation can all stimulate epinephrine. Epinephrine can become depleted with chronic stress or anxiety, leaving you feeling worn out, exhausted, mentally drained, and often depressed. Epinephrine is temporarily elevated when we exercise at very high intensity levels. Exercising at lower intensity levels, or performing intervals, [alternating intense exertion and rest] can lower epinephrine levels. Dopamine is the neurochemical that is responsible for sleeping and waking cycles. While we may not recognize when dopamine is correctly balanced, we certainly know when our sleeping and waking cycles have been disrupted. Commonly described as “jet lag”, a disruption in our sleeping and waking cycle is caused by an imbalance in the dopamine level. Dopamine stores can become depleted with chronic stress, or anxiety, and intense trauma, starvation or low carbohydrate diets. Dopamine can also be affected by serotonin levels, becoming depleted when serotonin is depleted. Likewise, dopamine levels can be elevated by elevating the serotonin level. Therefore, performing long duration exercise at moderate intensity can elevate dopamine levels. Endorphins are the neurochemicals that act as the body’s “natural painkillers”. Endorphins are responsible for the decrease in physical pain with exercise. Many runners will attest to the fact that chronic pains seem less noticeable during, and immediately after a run. Endorphins are also responsible for the ability to disregard, or perhaps not even notice pain, when engaged in a physical activity. This is why we can run, or play without noticing blisters on our feet, until after the run, or game. Endorphins can allow us to perform activities that would otherwise be stopped by pain. Endorphins are also partly responsible for the “runners high” that is often reported by devout runners. The endorphin response to exercise increases with frequency of the exercise. Interestingly, substance and alcohol abuse can deplete the endorphin response to exercise. However, all people, regardless of history, will experience a rise in endorphin levels with exercise of any kind.
Exercise, of any kind will have a positive effect on all four of our neurochemicals, but does the type of exercise we perform matter? To some extent, the answer is yes.
When we perform exercise at very high intensity levels, epinephrine levels tend to become elevated, more so than with low to moderate intensity level exercise. Power lifting, weight training, sprinting, interval training, plyometrics, and ballistic training can all create a rise in epinephrine levels. Likewise any sport that relies more on explosive, start and stop efforts than a consistent moderate intensity effort, would create a significant rise in epinephrine levels. This means that sports that utilize more fast twitch muscle fibers than slow twitch muscle fibers will have a noticeable impact on the epinephrine levels. When we recruit fast twitch muscle fibers, we create the same fight or flight response that would be created in response to real trauma. This response generates very high levels of epinephrine and adrenaline.
While explosive forms of exercise and sports generate a rise in epinephrine and adrenaline, low to moderate intensity exercise tends to create a rise in serotonin. Long distance running, cycling, hiking, swimming, yoga, and sports that rely more on endurance than power create a rise in serotonin levels. Therefore, any sport or exercise that recruits more slow twitch muscle fibers than fast twitch muscle fibers, will increase serotonin levels. When we recruit slow twitch muscle fibers, the purpose is to be able to perform moderate intensity exercise for a long period of time. While the chemical connection between moderate intensity exercise and increased levels of serotonin in not fully understood, one could speculate that completing a difficult task, such as a long run creates an increase in positive emotional states, which would positively affect serotonin levels. The rise in serotonin that is experienced with moderate intensity exercise, seems to be similar in nature to the rise in serotonin that is experienced when one is surrounded by good friends and family. In general, when one engages in positive experiences, including exercise at low moderate intensity levels, we see a rise in serotonin levels.
As indicated above, when the serotonin levels rise, the dopamine levels tend to rise in accordance. This means that exercising, or engaging in sports at low to moderate intensity levels would have a positive impact on dopamine levels. We have all experienced the good night’s rest that is typical following a good workout. However, we have probably also experienced the disrupted sleep that can follow intense exercise performed too late. It seem then that low to moderate intensity exercise has a positive effect on dopamine levels, while exercise that is very intense can lower dopamine levels, causing a disruption in sleep. In fact, one of the symptoms of overtraining is a disruption in the athlete’s sleep pattern.
While dopamine and serotonin are more strongly elevated by low to moderate intensity exercise, than with intense exercise, the endorphin response to exercise seems to be non-selective. We experience a rise in endorphins regardless of the type, or intensity of the exercise. However, the endorphin response to exercise becomes stronger with exercise frequency. It seems that the more exercise we perform, the more endorphins we produce with each exercise bout. While natural painkillers are never a bad thing, we do want to be careful of overtraining, which will disrupt sleep patterns, putting us at a greater risk of injury.
While we can begin to predict the neurochemical response to exercise, does this mean that we can control mood through exercise? Many researchers would answer yes. While, perhaps we may not thoroughly understand all of the mechanisms at play, we can say that different intensities of exercise create different chemical responses in the body. More than anything, however, we do know, beyond any doubt, that exercise has a very positive effect on mood. So try your hand at choosing the exercise that suits your personality best, and creating the mood you want. Happy exercising.
Next Sunday morning its my birthday, we’ve planned a long awaited trip to Kinder Downfall on Kinder Scout Mountain. Now that’ll be some birthday treat not to miss. 
