Healthier life: Your brain on exercise


KIRTLAND AIR FORCE BASE, N.M. — We have libraries of data documenting the benefits of exercise for the body. What about the brain?

Quite a bit of research collected over the past several years points to the conclusion that, yes, when you exercise, your brain benefits, too.

Exercise improves a variety of brain disorders, including chronic stress, anxiety, depression, memory loss, dementia, sleep deprivation, bipolar disorder, Parkinson’s disease, Alzheimer’s disease and post-traumatic stress disorder.

One way exercise helps the brain is by improving blood flow. Exercise causes blood vessels in the brain to increase in diameter, which increases oxygen supply and usage.

Moreover, exercise stimulates the production of proteins that promote blood-vessel growth, and this increases oxygen production.

Another benefit to having an increased number of arteries is this provides the brain with a greater reserve capacity. This may reduce the damage caused by a stroke, for example, as there are more arteries available to reroute blood flow around the area affected by the stroke.

Exercise also promotes the growth of new nerve cells, called neurons, and the connections between neurons, or synapses.

Exercise also boosts the density and number of dendrites, branch-like extensions of the neuron that transfer information from neighboring neurons. Furthermore, exercise increases a number of proteins that regulate the transmission of nerve impulses across synapses from one neuron to the next.

The development of new neurons, like the development of new blood vessels, may give the brain an increased reserve capacity in the case of neuron death from stroke or chronic stress.

Likewise, exercise has a positive effect on brain function by increasing the number, density, enzyme activity and efficiency of mitochondria. Mitochondria are the energy “powerhouses” of the brain, and produce the fuel — adenosine triphosphate, or ATP — that is used by every cell in the body to function.

Exercise also increases the capacity of mitochondria to make ATP, and ATP in the brain improves oxygen supply to neurons by increasing artery diameter. Moreover, exercise decreases brain oxidative stress, which prevents neuron death.

A very important role of exercise in relation to brain health is increased production of a protein called brain-derived neurotrophic factor, or BDNF, which has multiple effects on brain function. Levels of brain BDNF are low in patients with diseases such as Huntington’s, Alzheimer’s and Parkinson’s diseases, as well as depression and bipolar disorder.

Studies indicate that elevated levels of BDNF improve cognitive function and memory. BDNF is critical for the development, survival and growth of neurons, and research suggests BDNF increases resistance of neurons to damage from chronic psychological stress, sleep deprivation and Alzheimer’s disease.

In addition, a recent study found improvements in PTSD symptoms were correlated with increased levels of exercise-induced BDNF.

Another brain benefit from exercise is that exercise invokes changes in production of neurotransmitters — chemicals such as serotonin and dopamine — which carry nerve impulses across synapses from one neuron to another. Research indicates that exercise optimizes levels of serotonin and dopamine, which results in reducing anxiety, stress, fear and depression.

Most of us have probably heard of “runner’s high,” a sensation of euphoria associated with lessened anxiety and a reduced ability to detect pain. Recent research indicates dopamine levels in the brain are increased by up to 1.5 times from exercise, and genetic studies indicate that variations in dopamine genes are associated with differences in physical activity in humans.

Interestingly, our brain’s ability to respond to dopamine declines with age, which may explain in part why older adults are less physically active.

Another group of molecules that augments “runner’s high” is called endocannabinoids. Endocannabinoids are chemically similar to the active ingredient in marijuana, though in this case, these molecules are produced naturally in humans.

As with dopamine, endocannabinoid levels in the blood and brain are significantly increased by exercise, and animal studies document that if endocannabinoids are prevented from entering the brain, “runner’s high” does not occur.

Is there a “best” type of exercise for the brain? If the goal is to promote increases in neurons, it appears moderate-intensity cardiovascular exercise is most effective.

It doesn’t need to be running, however. Any mode of aerobic activity seems to work, so cycling, swimming and rowing are all good choices.

In addition, a growing body of research indicates mind-body exercises, such as yoga and Tai Chi, have mood-elevating, antidepressant and anti-anxiety effects.

It’s possible the mechanism by which yoga and Tai Chi reduce chronic stress, improve sleep and improve mental health is different than aerobic exercise. More research is needed in this area.

So, to sum up, when you exercise, your brain is along for the ride and exercises with you. One more reason to make physical activity a regular part of your lifestyle.