HomeHealthArchivesMay 2007

 

 

How Exercise Goes To Your Head

Q1 What is it about exercise that has fascinated scientists for years?

Muscle contraction has always fascinated scientists. How the body changes stored chemical energy into mechanical energy is a trick with no visible gears or pistons. How does the body get mechanical movement out of potatoes and gravy and other food in the diet? This question intriged scientists for many years until the answer was found with the development of the electron microscope that allowed us to see what was happening inside the muscle cells.

Q2 What did the electron microscope show us?

Nerves from your brain travel through the spinal cord and reach the muscle. In the muscle, the motor nerves branch out into fine nerve endings which reach the nerve cell. The point at which the motor nerve enters the muscle cell, an electrical impulse is transmitted from the nerve into the muscle. It travels from the nerve inside the muscle cells by way of small channels. These channels was invisible before the development of the electron microscope. With the electron microscope, these channels are clearly visible. They reach inside the muscle cells connecting the inside of the muscle cells with the motor nerve fibril.

Q3 What is the purpose of these channels inside the muscle cell?

Where the motor nerve ends at the motor end plate, a chemical is manufactured called acetylecholine which is the neurotransmitter which runs down the little tubules into the inside of the muscle causing it to contract or mechanically shorten. In the motor end plate an enzyme is also made called acetylcholinesterase that inactivates the acetylcholine. The balance between these two chemicals determines how much and for how long the muscle contracts. In order for the muscle to function properly, it has not only to contract, but it has also to relax. The enzyme that breaks down the chemical that causes the muscle to contract is necessary to get the muscle to stop contracting and to relax. If your muscles had too much acetylcholinesterase, they would go limp. If your muscles had too much acetylcholine, they would go into spasm. So it takes just the right amount of each of these chemicals for the muscles to function properly.

Q4 So how does acetylecholine change chemical energy into mechanical movement in the muscles?

The actual muscle contraction is brought about by the very rapid interaction between thin and thick filaments of proteins in your muscle cells. The thin filaments are made up of two proteins. The most plentiful protein making up most of the thin fiber is tropomyosin. Tropomyosin molecules are arranged together like a thin string of beads. Two of these strands of tropomyosin are twined together to make up the thin filament with a groove that spirals along the length of the filament. At regular intervals along the tropomyosin is another protein, troponin. This troponin protein plays a key role in muscle contraction as we will see in a moment.

The thick muscle filaments are made up of myosin proteins. The myosin molecule is shaped much like a golf club. There is a long handle and then a bump that is shaped like a pear of the head of a golf club. These myosin proteins are connected together with their handles all lying the same way - end to end with another set of myosin proteins making up the thick filaments of the muscle fiber. The golf club part of the myosin are symmetrically arranged in pairs. The club part of one myosin sticks out of the filament lying one way and the club part of the other lying the other way so that they make a series of bumps in rows. These myosin protein golf club heads oscillate back and forth and twist very rapidly on their necks with each oscillation. The myosin heads of the thick filaments are perfectly lined up with the spiral grooves of the thin filaments so that the oscillation of the heads causes the thin filaments to wind up and shorten. This is what makes the muscle fiber to shorten. We call that a muscle contraction. The details of this control has lots of detail that involves calcium ions and the troponin molecule working together to control the oscillating myosin golf clubs twisting up the thin filaments to shorten the muscle fiber.

Q5 What does it take to support all this protein oscillation and muscle fiber shortening?

Blood is required to bring in oxygen and glucose to support all of this oscillation and spinning up of the twisted pair of thin filaments in muscle contraction and relaxation. Heat is generated during all of this activity. The blood takes away the heat and radiates it away in the skin. If the skin gets too hot, water cooling is called into activity. We call this water cooling of the skin, sweat. The body is very efficient, if sweating is needed, the body relieves the kidneys and the liver and puts out waste substances in the sweat. The brain is fired up, because it is the nerve impulses that come from the brain that initiates and controls the muscle action. This is one of the ways that exercise goes to your head. More precisely, exercise comes from your head. However it has been shown that students who exercise regularly lean faster. They have better grades. Exercise help students learn to read. But we will get into that more later.

Q6 So what is the importance of exercise?

It has long been a maxim in the sports world: "If you don't use it, you'll loose it". What is becoming to be more and more appreciated today is that principle works for more than muscles. If you don't use your muscles, you will lose your muscles. However it is more than muscles you will lose if you don't use your muscles.

Q7 What is there more than the muscles themselves that are involved in exercise?

The brain is involved. There is no muscle contraction without a signal from the brain telling the muscle to contract. If the muscles contract when we don't want them to, for instance with an epileptic seizure, the problem is not in the muscles, but in the head. Epilepsy is a brain problem, not a muscle problem even though it is the muscles that are doing what we don't want them to do. So when we exercise, it is not only the muscles that are being worked, but the brain also. Physical activity enhances brain power. Inactivity is associated with less brain power. One of the ways to build your brain is to exercise.

Q8 So the same logic would show how exercise helps and strengthens the heart, lungs, bones and joints as well as the muscles. Could you tell us more about this Dr. Scribner?

There is more danger of rusting out than there is of wearing out.  The body is designed to repair damage to cells and tissues.  The effect of exercise is not weakening but that of strengthening the body.  This is true for every system of the body.

Q9 You have a special interest in adult memory and brain function symptomes, Dr. Scribner, does exercise really help the brain function significantly in this patient group?

Literature

Lifelong Exercise May Help Ward Off Alzheimer's Disease (1998).

MINNEAPOLIS--A new study suggests yet another benefit to regular exercise--protection against Alzheimer's disease. Among more than 370 people studied, those who did not have Alzheimer's engaged in significantly more exercise during their lifetimes than people with the disease, said lead researcher Arthur L. Smith, M.D., clinical research fellow at Case Western Reserve University in Cleveland. "These results suggest that lifelong regular physical exercise may be protective against the development of Alzheimer's disease," said Dr. Smith, who reported the findings here at the annual meeting of the American Academy of Neurology.

Previous studies have indicated that people with higher levels of physical, mental and social activity have less risk of developing Alzheimer's than people with less overall activity, he said, but this study is one of the first to look specifically at the impact of exercise. Exercise probably can't completely prevent the development of Alzheimer's but may be able to delay it, and thereby significantly reduce the prevalence of the disease, Dr. Friedland said. Exercise may help by preventing high blood pressure, stroke, and other cardiovascular diseases which are believed to increase a person's risk for Alzheimer's, Dr. Smith said.

Q10 Is there anything in the medical literature to support what we have said that exercise helps the whole body and many body systems including other aspects of brain function?

HEALTH PROMOTION - Exercise

Exercise can help reduce stress and have other positive effects on health unrelated to stress. If exercise is to be effective in inducing relaxation, it must be noncompetitive, moderate in intensity, and be done in pleasant surroundings. Physical fitness is associated with mental health and well-being, and can reduce stress-related emotions such as anxiety. "Exercise and Relaxation in Health Promotion," Shephard,Roy J., Sports Medicine, April, 1997;23(4):211-217.

Regular exercise has been shown to reduce the risk of triggered cardiac events which include myocardial infarction and sudden cardiac death. Further trials need to be done to prove or disprove the role of behavioral or pharmacological interventions in lowering the risk of acute cardiac events. "Mental Stress During Daily Life Triggers Myocardial Ischemia," Mittleman, Murray A.,M.D., Dr.P.H. and Maclure, Malcolm, Sc.D., JAMA, May 21,1997;277(19):1558-1559.

Q11 What is your advice to someone wanting to start an exercise program Dr. Foster?

I often tell patients who are trying to get on an exercise program that if they would add 30 seconds a week to a 5 minute per day exercise program, in a half a year they will be exercising over an hour a day.

Q12 What exercise would you suggest a person do on a regular basis?

Walking is the best exercise. There is a principle that the body is governed by. "Little attentions, often repeated" is advice for childhood training and education. This same principle works in every area of life. Walking is so good because each step takes little effort and is very low risk in terms of injury or becoming fatigued. However, it takes the whole body - the brain, the heart and lungs, the bones and joints as well as the muscles to walk. Thus walking is a wonderful exercise that I would recommend to any and all no matter what age or sex.