TAGS
In general, exercise improves the heart’s ability to pump blood and increases the natural ability of blood to carry to cells throughout the body. With exercise, blood circulation to the brain is thus increased and the brain receives more and , both of which are crucial to brain function. The brain is the body’s most active organ and it requires the most energy. Although it 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 or . It is therefore necessary for the blood stream to deliver a constant supply of these substances, and it does this by circulating continuously through the brain. A person can feel a lack of 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 can drop their blood level and faint, and can die unless they quicklyincrease the level of in the brain. Adequate blood circulation and the vast network of that serve the brain and allow for blood flow are thus critical. The 400 miles of 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 , , and other important nutrients to the brain, blood flow to and from the brain also removes harmful toxins. So overall, having a proper functioning (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 to bring the extra blood to nerve cells. This process, known as , is directly connected to , the process of making new nerve cells. It was initially believed that , much like , was limited to certain periods of development or in response to pathological insults. It has since been discovered that naturally occurs when physical activity is increased, and can be induced by exposure to a complex environment or exercise. Thus, the formation of new is not restricted to developmental periods but extends into mature adulthood and beyond. For example, in the , a brain structure that experiences a great amount of on account of HD, new nerve cells are clustered close to . 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 contributes to the decline in new production among older individuals. Moreover,exercise has been shown to increase and proliferation throughout the brain in various 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 and . In a test, students had a one-minute blast of given to them immediately before being given a list of words to remember. On average, the students who took the remembered two to three more words from a list of 15 than those who did not. Students who took 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 . If performed on a consistent basis, exercise has the effect of providing a dose of continuous to the brain, such that the boosts can be continually maintained as well. The increase in blood circulation because of exercise can induce the formation of new that can, in turn, facilitate the creation of new nerve cells.
Even people who do not have HD experience a moderate amount of as part of the normal aging process. Here, the signals that nerve cells use to communicate with one another become less powerful and less efficient. This decreased ability for nerve cells to communicate makes it harder for the brain to adapt to outside influences and generate new nerve cells. The inability to create new nerve cells leads to losses in brain tissue and impaired functioning. Indeed, imaging studies in elderly humans have shown some noticeable in the brain. In people with HD, this is substantially magnified. One of the consequences of is that older adults typically perform more poorly than younger adults on a broad range of measures. (For more information on of HD, )
Despite such declines in and motor processes during the course of aging in people with HD, recent findings suggest that physical exercise can minimize some, but not all, kinds of decline. A recent study showed that older adults who exercised throughout life had less brain tissue loss and performed significantly better on tests than adults who exercised infrequently. Similarly, a study with twins done in Sweden found that the twin who exercised more was also more likely to score higher on a test. It is important to note that these tests show and do not necessarily prove causation. In other words, just because people who exercise a lot show increased abilities, this does not necessarily mean that one causes the other. For example, people who exercise more may also have better eating habits such that improved nutrition leads to better scores. Nevertheless, as indicated by the numerous studies discussed below, the role of exercise in maintenance should not be discounted.
It turns out that the areas in the brain that are associated with mental decline due to aging are the same areas that are the most responsive to exercise. Researchers have found that people who exercise a lot have more and in the brain, particularly in the frontal lobe, , and parietal lobe. The lobes of the brain are composed of and . is where all the nerve centers are located. connects the together. (For more information about the brain and its structures, .) The amount of and declines naturally, affecting the functioning of the lobes and contributing to a decline in functioning and processing ability.
It has been found that individuals with HD typically have a substantially reduced volume of and in the brain, especially in the and the frontal lobe. This is significant, given the prominent roles that each of these lobes play in the processes. The of the brain have a lot to do with what people call higher-level , where we synthesize information, and store data we’ve just acquired. If the are not functioning properly, then you can easily forget a phone number you just looked up or the name of a person you just met. The temporal lobes consolidate short-term memories and build them into long-term memories. Damage to temporal lobes can also result in personality and affective behavior. The allow us to construct a spatial coordinate system to represent the world around us. Damage to the can result in neglecting part of the body or space, which can impair many self-care skills such as dressing and washing. (For more information about the lobes of the brain, .) Deterioration of each of theselobes is associated with some sort of mental decline. Exercise appears to exert its effects partially by protecting against a loss of and , thereby preserving the structure and function of the lobes in the brain. With the lobes able to function better, the onset and progression of various deficits are likely to be delayed.
The fact that some degree of is part of the normal aging process means that a person with HD must deal with these changes in addition to disease-related loss. Preserving function and preventing mental decline is definitely an uphill battle and some amount of is inevitable. But this does not mean that the situation is hopeless. Studies on exercise reveal that it may indeed play an influential role in slowing down decline. As the rest of this chapter reveals, exercise exerts numerous other beneficial effects throughout the body and is thus a wonderful practice to incorporate into the daily routine. Later in this chapter, we’ll give some suggestions for where to begin.
In addition to keeping the brain’s lobes healthier and more intact, physical exercise can act directly on the brain’s molecular machinery. There is increasing recognition that physical activity can help relieve the effects of deterioration of function. Numerous scientific studies with animals have reported that voluntary exercise leads to an increase in production of . This is a kind of that aids in the growth and survival of nerve cells during development, and in the maintenance of adult nerve cells. Because has both neurotrophic and properties, it is able to significantly influence brain plasticity. (For more information on ,)
HD invariably leads to decreased levels of , leaving nerve cells more vulnerable and prone to injury or death. In people without HD who have the , the indirectly activates the , or the “on” switch, of the that encodes . When this is turned on, it prompts nerve cells to make more . In people who have HD, indirectly inactivates the “on” switch so that can no longer be produced. In the absence of , the ’s ability to survive is markedly decreased.
Currently, scientists are looking for ways to harness neurotrophic factors such as so they can be administered to patients. This treatment would theoretically improve the of people with disorders because it would dramatically improve the health and survival of the person’s nerve cells. Animal studies and both indicate that is capable of making damaged nerve cells regrow. Because of this capability, represents an exciting possibility for reversing brain disorders, such as HD. The fascinating part of is that the can naturally be increased through exercise. In one rat study, several days of voluntary wheel-running increased levels of . The changes in levels were found in nerve cells within days in both male and female rats and were sustained for several weeks after exercise.
In particular, running activity increases levels of in the lumbar spinal cord, , and , but not in the . Since the main site of in people with HD is the , exercise alone will likely not be able to prevent many of the of the disease. However, exercise can help preserve function and promote the general health of the brain, as well as the general health of the body overall. Although exercise may not be able to promote (the growth of nerve cells) in the , it may promote in other areas of the brain and body by increasing the vitality of nerve cells. These changes may be enough to delay the onset and progression of various HD .
Exercise may also help the brain to better cope with . leads to the release of various and hormones. (For more information on and its effects on the brain, .) Prolonged exposure to hormones is detrimental to the health and survival of nerve cells. Normal nerve cells are like miniature trees with a lot of branches. These “branches” are called . They are structures that connect one to many other nerve cells. hormones cause the branches of the to become shorter and less widespread, such that the affected cannot connect to as many nerve cells. With fewer connections, it does not receive as much information as it should, and becomes more prone to injury or death. It is thought that this effect occurs mainly because hormones decrease the amount of in the brain, depriving nerve cells of neurotrophic factors necessary for growth and survival. Exercise directly counteracts this effect by increasing availability in the brain. As evidence, in a study in which two groups of rats were exposed tostressful stimuli, the effect of exposure to this was mediated by exercise. Rats that were able exercise before exposure to the stressful stimuli had normal amounts of in the brain, whereas rats that were not able to exercise had significantly decreased amounts of in the brain.
In addition to increasing availability, exercise also helps regulate the release of harmful hormones, so that they don’t flood into the nerve cells and wreak havoc. Researchers first became interested in exploring a possible link between exercise and after discovering that physically fit individuals have significantly lowered rates of anxiety and depression. Although popular theory states that exercise causes a rush of , there is very little evidence for this phenomena. Instead, researchers believe that a chemical known as plays a key role in helping the brain deal with more efficiently. During exercise, norephinephrine is released and goes on to directly increase heart rate, release energy from fat, and increase muscle readiness. Studies in animals since the late 1980’s have found that exercise increases concentrations of in regions of the brain involved in the body’s . Although the exact mechanism is not known, increased in the brain is thought to decrease the release of otherharmful chemicals. In fact, some antidepressants work by increasing brain concentrations of .
Many physiologists believe that exercise also enhances the body’s ability to respond to in a more general way. Biologically, exercise seems to give the body a chance to practice dealing with . It forces the body’s systems, all of which are involved in the , to communicate much more closely than usual; e.g. the system communicates with the , which communicates with the . All are controlled by the central and , which must also communicate with each other. This “workout” of the body’s communication system may be the true value of exercise; the more sedentary we get, the less efficient our bodies become in responding to .
The widespread effects of exercise should not be surprising considering that the human body evolved in an environment of regular physical activity. Biologically, it was part of survival. Physical capability was necessary for success at hunting, gathering food, and providing shelter and safety. What is now considered a form of exercise – walking – was originally a form of transportation.
Today, many people see physical movement as an optional part of their lifestyles. This type of thinking is unfortunate considering the integral role that exercise plays, not only in general health, but also numerous and molecular cascades that protect the brain. Not surprisingly, a lack of exercise is linked to increased of many diseases. Additionally, the ability to perform day-to-day activities declines: to walk without falling, to rise from a chair or get in and out of a car unaided, to carry a bag of groceries, to tie shoes, etc. Although human lifestyles have changed, and exercise is no longer a necessary part of our daily survival, our bodies still need exercise. We must consciously make an effort to incorporate some sort of physical activity into our daily life routine.
During the progression of HD, a person will decline in health and be forced to lead a more sedentary lifestyle. Although the disease process can’t be , a routine exercise program can help to address many areas of decline, as well as increase strength, improve balance and posture, and allow the individual to feel more in of his/her body. Aerobic activity, such as pedaling, jogging, or walking, may improve breathing, which in turn may help with breath for talking and eating. Improvement in deep breathing will also help maintain the ability to cough effectively, which helps prevent choking and . Regular exercise also makes it easier for people to clear secretions more efficiently when they do have colds or . Growing evidence shows that physical exercise does not have to be strenuous or even require a major time commitment. It is most effective when done regularly, and in combination with a brain-healthy diet, mental activity, and social interaction.
Physical activity is any bodily movement that burns calories, such as gardening, vacuuming, shoveling snow, walking to the store, climbing stairs, or playing ball with your grandchildren. As such, anyone can improve their physical fitness, regardless of age or physical condition. In fact, the greatest improvements are often seen among the frailest individuals who are nurtured through an exercise program. The easiest, safest, and most readily available physical activity for a person with HD is walking. It can be combined with a purposeful activity, such as walking a dog, pushing a person in a wheelchair, walking to the store to buy a newspaper or groceries, or picking up trash in the neighborhood.
Convincing people of the benefits of exercise is an first step. Many people with HD are worried about becoming a burden to their families. Explaining that exercise can help keep them healthy and make caregiving easier on their loved ones can be a strong selling point. But it is first important to consult with a physician before embarking on an exercise program. A health history and physical may reveal cardiac, musculoskeletal, or other problems that may impose restrictions on the type and intensity of exercise to be undertaken. If this is the case, request a referral to a physical therapist or cardiac-rehab specialist to work out a beginning regimen that is suitable for the individual. It may help to ask the person’s physician to reinforce his or her exercise recommendation by writing out a prescription that can be shown to the individual periodically. Such an instruction carries more weight than suggestions from a caregiver. The key to motivating people to persevere in any program oflifestyle change is social support. Fitness club membership lists are filled with names of people who rarely come to work out after an initial “honeymoon” period. Many home treadmills, exercise bikes, and other equipment are unused after this initial period. Exercise programs for persons with disabilities that are successful are all characterized by the presence of exercise “buddies” or program monitors that provide ongoing supervision and encouragement.
.
