by Dr. Sheri Colberg, Ph.D., FACSM
Continuing from my last column, here are additional reasons why your brain needs for you to be active related to changes in your brain hormones. Your brain can’t afford for you to be sedentary, at least not if you want to live long and well.
While it has long been known that working out immediately elevates your post-exercise mood, we now know that your mood is improved via rapid changes in an area of the brain called the dentate gyrus, which is integrally involved in managing stress and depression. When you exercise, brain chemicals called endorphins get released and interact with brain receptors that reduce your perception of pain. These chemicals are thought to be related to feelings of euphoria during exercise often referred to as a "runner’s high" that can lead to a positive outlook and greater energy levels. Serotonin release, which also occurs during physical activity, is associated with short-term improvements in mood as well.
Exercise also increases levels of a brain-derived neurotrophic factor (BDNF), which helps nerve cells transmit information better. Low levels of BDNF have been associated with depression, making BDNF enhanced by exercise can be a natural antidepressant with potentially more long-lasting effects than a surge of endorphins. Although it is possible to get "addicted" to exercise, in most cases being physically active creates new, positive addiction pathways that can counter negative behaviors grounded in addiction.
Physical activity has been shown in many studies to reduce mental stress, anxiety, and depressive symptoms, likely for the same reasons that it elevates mood. In many cases, treating anxiety or mild to moderate depression with participation in regular exercise is at least as effective as, if not more so than, using medications to treat these symptoms—and the side effects from being regularly active are much more positive.
Exercise is also considered vital for maintaining mental fitness. It effectively reduces fatigue, improves alertness and concentration, and enhances overall cognitive function, all while reducing symptoms of stress and anxiety. In effect, regular participation in aerobic exercise decreases overall levels of tension, elevates and stabilizes mood, improves sleep, and enhances self-esteem, and even just five minutes of aerobic exercise can stimulate anti-anxiety effects. What better medicine could there be for what ails you emotionally?
The common denominator of addictions of all sorts is an out-of-control reward system. As a treatment, exercise works from the top down in the brain, forcing addicts to adapt to a new stimulus, which allows them to learn alternate, healthier scenarios. Addictions are associated with the release of dopamine in the nucleus accumbens, the "reward" center of the brain. Exercise can boost the levels of dopamine in the brain in these same areas. Parkinson’s disease is caused by damage to the neurons in the substantia nigra, a region of the basal ganglia that is responsible for creating much of the brain’s dopamine, and progression of the disease ultimately leads to muscle tremors, stiffness, and an inability to control motor movement. Interestingly, physical activity of all types is an emerging treatment for individuals with Parkinson’s because of its natural ability to boost dopamine in the brain, and it’s also being used as therapy for MS. Yoga and tai chi are alternate activities that have been used to successfully mitigate some of the symptoms of this degenerative brain disease.
Exercise has also been used effectively as a treatment for children diagnosed with attention deficit hyperactivity disorder (ADHD). When kids walk, run, or do a set of jumping jacks or pushups, their brains releases several important chemicals. Endorphins, for one, are released; they are hormone-like compounds that regulate mood, pleasure, and pain. That same burst of activity also elevates the brain’s dopamine, norepinephrine, and serotonin levels. Particularly when dopamine levels rise, the ability to be attentive increases—which is important for anyone with an attention deficit of any sort. The focus of exercise has expanded beyond endorphins to include endocannabinoids, another class of neurotransmitters that dull pain. In fact, exercise, marijuana, and chocolate all activate the same receptors in the brain, and two of these endocannabinoids are produced in the body and brain during exercise.
Since dopamine does more to regulate fine motor control during physical activity than anything else, why is its release so important for your brain health? It’s because dopamine also facilitates the brain association of physical activity with the elevated sense of delight that accompanied the exercise. In other words, your brain will recall the pleasant feelings associated with fitness training and be more likely to encourage you to want to continue doing activities that replicate that pleasurable sensation.
Research suggests that physical movement increases brain serotonin function in the human brain. Physical activity of any type increases the firing rates of serotonin neurons, resulting in increased release and synthesis of serotonin. Its release has been directly linked to feelings of joy, resulting in less frequent or severe depression. Furthermore, individuals who engage in frequent physical activity have more serotonin present in their brains and tend to be happier overall than their sedentary counterparts. In addition, exercise-induced increases in the serotonin precursor, tryptophan, persist after working and may allow for greater serotonin production after you exercise and improve your mood both during and following any activity. Physical movement of any type also helps restore and elevate serotonin levels when you’re feeling stressed. Exercising outdoors can be particularly beneficial given that exposure to sunlight itself helps boost serotonin levels in the brain.
My next column about brain health (Part 3, the final one) will cover changes in leptin and other hormones that result from physical activity. In addition, you’ll find out more about which types of physical activity are best undertaken for optimal brain health and weight loss.