Physical Exercise and HD
Part 1

Exercise and Capillary Density

In general, exercise improves the heart’s ability to pump blood and increases the natural ability of blood to carry oxygen to cells throughout the body. With exercise, blood circulation to the brain is thus increased and the brain receives more oxygen and glucose, both of which are crucial to brain function. The brain is the body's most active organ and it requires the most energy. Although is accounts for only 2% of our body weight, it uses between 20% and 30% of the body’s energy. Despite this need for a large amount of energy, the brain can not store any oxygen or glucose. It is therefore necessary for the blood stream to deliver a constant supply of these essential substances, and it does this by circulating continuously through the brain. A person can feel a lack of oxygen after only a few seconds. When you stand up too quickly and become dizzy, this is an example of loss of blood flow to the brain that can be sensed. Diabetics who give themselves too much insulin can drop their blood sugar level and faint, and can die unless they quickly increase the level of glucose in the brain. Adequate blood circulation and the vast network of blood vessels that serve the brain and allow for blood flow are thus critical. The 400 miles of blood vessels in the human brain have a surface area of approximately 100 square feet. The health of these vessel walls is very important for proper brain function. In addition to delivering a constant supply of oxygen, glucose, and other important nutrients to the brain, blood flow to and from the brain also removes harmful toxins. So overall, having a proper functioning vascular (blood vessel) system is absolutely necessary for optimal brain health and functioning.

When blood flow to the brain is increased, the body responds by forming new blood vessels to bring the extra blood to nerve cells. This process, known as angiogenesis, is directly connected to neurogenesis, the process of making new nerve cells. It was initially believed that angiogenesis, much like neurogenesis, was limited to certain periods of development or in response to pathological insults. It has since been discovered that angiogenesis naturally occurs when physical activity is increased, and can be induced by exposure to a complex environment or exercise. Thus, the formation of new blood vessels is not restricted to developmental periods but extends into mature adulthood and beyond. For example, in the dentate gyrus, a brain structure that experiences a great amount of neurodegeneration on account of HD, new nerve cells are clustered close to blood vessels. These nerve cells can only grow and be healthy when there is enough blood flow to the brain. Researchers believe that decreased blood flow to the brain as a result of fewer blood vessels contributes to the decline in new cell production among older individuals. Moreover, exercise has been shown to increase angiogenesis and nerve cell proliferation throughout the brain in various animal models like mice and fruit flies.

It turns out that there is a good reason why exercise seems to "clear your head." Your heart rate increases as you exercise, increasing blood flow to the brain, which enhances waste removal and provides much-needed oxygen and glucose. In a test, students had a one-minute blast of oxygen given to them immediately before being given a list of words to remember. On average, the students who took the oxygen remembered two to three more words from a list of 15 than those who did not. Students who took oxygen while playing the Tetris computer game on its most demanding level were also shown to play significantly better. Exercise can act very similarly to having a one minute blast of oxygen. If performed on a consistent basis, exercise has the effect of providing a dose of continuous oxygen to the brain, such that the cognitive boosts can be continually maintained as well. The increase in blood circulation because of exercise can induce the formation of new blood vessels that can, in turn, facilitate the creation of new nerve cells.

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Last Modified: 04/12/2007

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