Why Exercise?

Joshua Landau

Why should I exercise? Just listen to commercials and they’ll tell you: Just do it! Too bad, but that’s not good enough anymore. What drives crowds and crowds of women into spandex every day? What is the attraction for the middle aged man to strap on a pair of roller blades and take to the hills? Why can’t everybody just be content to sit down with their Haagen-Daz and enjoy watching their favorite athletes pound the court. They are professional. They get paid more money than I’ll ever see to exercise. So why should I exercise? If the recent health kick has left no one unbruised, then why do we keep coming back for more? Exercise does more for you than just wear you out. Before we ever were the intellectual giants (Ha!) that we have become, human beings were functional physical organisms. Whether you believe in evolution or creation, our bodies were built for action. The instruction manual to the human body is not that complicated: Use it or lose it! Our bodies adapt gloriously to exercise, even after we’ve hit warranty. Exercise is the most fundamental celebration of the beauty of the human body. Although sometimes we may feel like we have woken up with a mean hangover, our bodies ultimately reward us for living an active vigorous life. But what are these rewards? How does the body let us know “Exercise does a body good”?

Exercise causes some real physiological changes in your body. A lot of people are motivated to exercise to burn off the extra calories that they have eaten. Depending on your age, heredity, and many other factors, your body burns somewhere around one thousand calories every day just to carry out the basic functions of life. These calories are used for things like heartbeat and breathing. The calories your body burns just to keep itself alive is called your resting or basal metabolic rate. The total number of calories that your body consumes is the sum of calories consumed by your resting metabolic rate plus the calories burned from the food you eat plus the calories consumed during exercise. What people don’t usually realize is that exercise burns calories during the exercise period itself, as well as the during the hours afterward when the body is recovering. The amount of muscle mass also independently determines the resting metabolic rate. An athlete at rest will burn more calories than a couch potato at rest. This is why some athletes you know may eat and eat and eat without ever putting on weight. The idea is really pretty simple. When you exercise, you use up energy. Your muscles and your liver are exhausted of sugar and some fats. It then takes energy to replace that energy (the glucose and fats). Your body must replace what you have lost. So in a sense, exercise gives your body a double whammy. When you ride the exercise bike for thirty minutes the machine may tell you that you have burned something like 400 calories. This number is only a calculation of how much work was done by cranking the pedals around and around against a measured resistance. What it doesn’t tell is that your body actually burns at least that much during the period of rest just after you finish working out. The exercise activates your metabolism to burn more calories.

How does your body burn more? Where does the food get “burned”? Some of you may have learned what mitochondria are from ninth grade biology. Mitochondria are basically the power plants found inside the cells in your body. They take sugar (glucose molecules) and break them apart until all that is left is a bunch of carbon dioxide. If you exercise on a regular basis, you can actually double the amount of mitochondria in your body! The more mitochondria present in your cells, the more little power plants there are demanding fuel to burn. If you have twice as many power plants, not only can you burn more calories, but you also produce more energy. This is why people who are out of shape may complain that they always feel tired, lazy, or sluggish. They may be lazy, but that is another story. People who exercise on a regular basis often report having more energy throughout their day than those who rarely exercise.

So far we have seen that exercise increases your resting metabolic rate as well as your energy levels by doubling the amount of mitochondria in your body. How does it do this? Increased mitochondrion also improves the rate at which you can consume oxygen. Because you burn 5 kcals (1 kcal is the same as 1 calorie) for every liter of oxygen consumed, if you can consume more oxygen, you can burn more calories faster. This allows access to energy faster. More mitochondrion also improves the rate at which your body metabolizes fat. Exercise will jump start your body into action.

Exercise not only improves your body’s ability to process fuel, but it also improves your body’s ability to circulate fuel. A trained athlete’s heart can pump about 20% more blood with each contraction than an untrained person. In comparing a cross-country skier with an average man during intense exercise, both have hearts that beat at about 185 times per minute. However, during that 185 times, the untrained man only pumps 16.6 liters whereas the skier pumps 32 liters! In addition to improving the amount of blood your heart pumps with each beat, exercise has a number of other effects on the circulatory system. Your body does not circulate blood through every one of its blood vessels at all times. This is painfully obvious if your leg falls asleep. Exercise opens up many of the unused capillaries to improve circulation and allow more oxygen to get to your muscles. Because exercise improves the body’s ability to circulate blood, as someone gets more in shape, they are able to supply their body with oxygen for longer periods of time. This is why someone in shape is able to workout for so much longer than someone who is out of shape.

Improved circulation and training also improves the body’s ability to clear away the lactic acid produced during exercise. This way, when a muscle becomes fatigued and releases lactic acid, your body can clear it away faster so that the muscles keep working. The lactic acid makes you feel tired and exhausted. Lactic acid also prevents the burning of fat storages, so if you can clear away the lactic acid faster, you improve the amount of fat that you burn. This slows the burning of all the muscle glycogen (sugar) thus preventing muscle exhaustion. If you haven’t noticed already, everything is related. Exercise improves ability to process energy, as well as the ability to circulate energy. Improved circulation prevents exhaustion and improves fat utilization which accesses the huge banks of energy storage in the adipose tissue.

If you are trying to lose weight, all these things are important. Another thing that exercise does that will help you lose weight is it will reduce your appetite. Not only does it occupy time that you are not browsing the refrigerator, but it also draws all the blood from your stomach to your muscles. This way you forget about being hungry and concentrate on exercising. This is also the same reason that it is not safe to swim just after you have eaten. Your body has sent blood to your stomach to digest the food. Then it must take the blood away from the stomach and supply the muscles with enough fuel to keep you from drowning. Then your muscles cramp up and refuse to work because they are not getting the oxygen they need.

Another effect that exercise has on your body is to mobilize your joints. “Use it or lose it” is no joke. If your joints and muscles don’t go through normal range of motion on a regular basis, they stiffen up. Even on as little as a three hour car ride, when you stand up your legs may be stiff and your back will probably be sore. Exercise stimulates blood circulation to all the parts of your body keeping everything well regulated and well supplied with the nutrients needed for growth and function.

Faster metabolism will not only break down carbohydrates and other fuels faster, but it will also metabolize cholesterol and low density lipids faster. Cholesterol and low density lipids are responsible in part for deposits on the walls of the arteries. Exercise will help prevent excess deposits of cholesterol on the walls of the arteries. It also lowers high blood pressure. Overall it may be one of the most effective means of fighting heart attacks, atherosclerosis, and strokes.

For many people, exercise is a release. Many people go into the gym just to get away and forget all the stressful problems they have to deal with. The physical labor itself actually helps relieve mental stress and anguish. It may have something to do with some of the endorphins or other hormones released, but exercise definitely helps relieve psychological tension built up and often stored in muscles in your body such as your back or shoulders.

In our extensive coverage of physiology and adaptations to exercise, I have left out the most important and most rewarding aspect of exercise: It is fun!! There is nothing more fun than a great game of basketball or a beautiful bike-ride through the mountains. Exercise is not a chore. If you are exercising just to burn calories or just for any of the other physiological effects, you are missing the biggest reward. Exercise to be alive! Be alive to exercise! Don’t exercise for maintenance, or to improve your aerobic capacity, exercise because your body loves life!