Mike Clark is an Exercise Physiologist and Personal Trainer at the Duke Center for Living at Fearrington. He received his BA in Exercise and Sports Science from UNC.
It is well established that a structured exercise program can help prevent heart disease, stroke, cancer, and obesity. But what about the brain? When I was in the exercise science program at UNC we talked about endorphins, and how they increase with exercise to provide that “runner’s high” after a vigorous exercise session. But that was about it. Today there is a lot of research into how physical activity benefits the brain, which goes well beyond helping you feel better a couple of hours after the exercise session. Currently, there are three emerging benefits for the brain that scientists are currently studying.
To begin, the brain can be likened to a computer, with both hardware and software. The brain’s “hardware” consists of the actual cells and structures that form the brain, like cells called neurons, gray and white matter, and different sections to carry out clear-cut functions within the body, much like the medulla oblongata regulates heart rate and breathing rate. The “software” consists of cognition, moods, mental states, memories, and other less tangible qualities. You will be happy to see that physical activity and exercise can aid both the brain’s software and hardware.
The first notable benefit is software related, in that cardiovascular fitness levels have been shown to affect the symptoms of depression in both depressed and non-depressed people. Depression, 1 of the 4 recognized mood disorders, affects roughly 1 in 10 Americans each year. In a twelve-year follow up study published in 2009, researchers measured the depressive symptoms and cardiovascular fitness of eleven thousand men and three thousand women. The results showed that as fitness levels increase, depressive symptoms (i.e. feelings of hopelessness) decreased. The researchers concluded that men and women with the lowest level of cardiovascular fitness were at the highest risk of experiencing depressive symptoms. Additionally, over 25 previous studies show that physically active individuals have a 33% reduction in depressive symptoms, regardless of race, age, or medical condition. Additionally, if depression is already present in a sedentary individual, exercise can be a valuable therapy for decreasing the symptoms, much like antidepressants and talk therapy.
The next benefit is both software and hardware related, in that studies show that physical activity reduces the risk of cognitive decline in adults and older adults. Cognitive decline comes in the form of Alzheimer’s disease and other dementias, which can decrease brain cell number and brain mass, along with negatively impacting thought processes, memories and even moods. While the mechanisms that provide the exercise benefit are still unclear, studies show that cognitive function increases when individuals exercise, with the largest increases coming by way of executive function (i.e. decision making, etc). Dr. Bonita L. Marks, an exercise researcher and neuroscientist at UNC-Chapel Hill and Duke University writes about exercise and the brain: “it seems that physical exercise helps to maintain/preserve the structural integrity of the brain, presumably by facilitating better delivery and uptake of needed hormones, which are responsible for maintaining the existing brain cells and creating new ones. When we have healthy brain cells able to transmit thoughts effectively, we have better memory processes and can remember all the important things, like where you parked your car or where you last put your keys.” Multiple research studies are finding the same effect as Dr. Marks’.
The final benefit to mention is hardware in nature. Neurogenesis is defined as the development of new nervous tissue, and in the case of exercise training, new brain cells. While it was once thought that brain cells could not be replaced once destroyed, MRI and other advanced imaging techniques have proven otherwise. Surprisingly, neurogenesis is a process that takes place throughout life; though the rate slows as age increases. In studies of active and sedentary mice, researchers observed that the sedentary mice experienced normal decreases in neurogenesis and brain size. Exercising mice, however, maintained higher levels of neurogenesis and higher brain sizes, in spite of increasing age. What is also interesting is that there seemed to be higher brain volumes in the mice who exercised early in life, suggesting that the aerobic training may have had an accumulative effect on the brain. Exercise induced neurogenesis has also been observed in humans, and more studies are being conducted on if the new brain cells actually aid in learning, memory, daily function, and the prevention of cognitive decline.
The amount of exercise needed to provide the brain benefit is still under scrutiny. The current exercise recommendation calls for jogging, or an equivalent activity, twenty minutes, 3 days a week, or brisk walking for thirty minutes, 5 days per week. While these recommendations are based primarily on heart health and the prevention of chronic disease, Dr. Marks and other researchers believe this amount of exercise will also apply to brain health.