Brain-Body Chemistry

Physical activity is intricately related to ongoing brain development. This process begins at the earliest age when a child’s first movements stimulate brain growth, and continues throughout life unless one stops being active. This activity increases levels of a family of natural protein-based chemicals in the brain called neurotrophins. Perhaps the most researched chemical includes brain-derived neurotrophic factor (BDNF), which promotes cellular growth and repair in the brain and body. BDNF improves brain function by helping cell-to-cell communication, important for learning, memory, and overall cognition. BDNF also stimulates the production of new brain cells—a process called neurogenesis—and protects cells from degeneration, associated with a decline in brain function with age. Physical activity also stimulates BDNF to help mobilize gene expression, switching on many of the genetic benefits programmed within the body while turning off the bad genetic profiles. Even an easy workout can benefit the brain in another way, by promoting plasticity—the ability to improve overall brain function at any age. Those individuals with depression, Alzheimer’s disease, and other brain disorders often have low levels of BDNF. Even those with high body fat, diabetes, and other conditions are low in BDNF.

BDNF also affects our muscles by helping them function more effectively through improving contraction and fat burning for energy production throughout the body. And BDNF is considered a key chemical for overall human survival—something we don’t think much about these days, but a long endurance event is just that: a test of survival that relies heavily on optimal brain and muscle function.

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Which workouts are best for brain health? The answer is any training that promotes overall health, especially those that are aerobic. This can even include an easy walk, regardless of one’s level of fitness.

For endurance athletes, the brain’s most important job is to preserve the body’s delicate physiological mechanisms to prevent injury, ill health, and possible death in the extreme circumstances of tough endurance races. Even during competition, when one’s more rational thoughts sometimes get lost in the heat of the battle, the brain will pick up the slack. If you consciously decide, for example, to keep up with the lead pack in a cycling event, despite a usual finish in the middle of the pack, your brain will prevent that attempted high level of effort—subconsciously slowing you down by reducing muscle power. This natural decrease is ultimately for your benefit.

Another common way the brain protects athletes is through its ability to help the body physically compensate for problems such as muscle imbalance. Our eyes play a key role in this physical balance. (The brain also relies on the inner ear’s delicate nerve endings to control balance by sensing body motion and adjusting muscle activity.)

Our eyes, which are part of the brain controlled from within, can influence the muscles throughout our body and even change our running, cycling, or swimming form for better or worse. Here’s an example. Normally, vision is very high up on the brain’s list of priorities; the brain dedicates a significant amount of neurons and energy to visual activity.

Through visual input, the brain will maintain body balance even at the expense of muscles in the neck, shoulder, lower back, and legs. Here’s why. It’s important that the normal position of both eyes resides in a horizontal plane for optimal function. If muscle imbalance in the neck causes the head to tilt, the eyes may not maintain their normal horizontal position. This is because muscle imbalance can cause the head to tilt slightly to one side, causing the eyes to lose their normal horizontal balance. When this happens, the brain must immediately compensate in the easiest and best way to bring the two eyes back to balance. If the problem muscles in the neck can’t be corrected by the brain, other types of compensation are attempted. The brain can do this by creating an opposite imbalance in other muscles, slightly tilting the spine and pelvis to accomplish this task. While this restores the eyes to their normal position, it’s done at the expense of other muscles, which now don’t function as well. Some of these muscles may be key to the process of running or biking, reducing our effectiveness and altering our form. In addition to slowing us down, it also increases the risk of additional secondary muscle problems and increases stress on joints and other mechanical areas such as ligaments and bones.

This example is very common; just watch marathoners approaching the finish line and you’ll see some who are literally, physically twisted—wounded by the brain’s compensation. But if the brain didn’t act accordingly, the athlete may not have ever completed the race.

By remaining fit and healthy, one can usually prevent the original imbalance in the neck, which caused the eyes to become stressed, thereby eliminating the need for the brain to make such dramatic compensations.