What happens when we exercise?

Mostly the accepted thinking that pain is part and parcel of working out and one must learn to live with it.  There are many causes for pain, soreness, discomfort during exercise in order to identify them lets look at what happens when  we exercise:

Any type of exercise uses your muscles. As you use your muscles, they begin to make demands on the rest of the body. In strenuous exercise, just about every system in your body either focuses its efforts on helping the muscles do their work, or it shuts down.

For example, your heart beats faster during strenuous exercise so that it can pump more blood to the muscles, and your stomach shuts down during strenuous exercise so that it does not waste energy that the muscles can use.

When you exercise, your muscles take in a source of energy and they use it to generate force. Your muscles are like biochemical motors, and they use a chemical called adenosine triphosphate (ATP) for their energy source. During the process of "burning" ATP, your muscles need three things:

• They need oxygen, because chemical reactions require ATP and oxygen is consumed to produce ATP.
• They need to eliminate metabolic wastes (carbon dioxide, lactic acid) that the chemical reactions generate.
• They need to get rid of heat. Just like an electric motor, a working muscle generates heat that it needs to get rid of.

In order to continue exercising, your muscles must continuously make ATP. To make this happen, your body must supply oxygen to the muscles and eliminate the waste products and heat. The more strenuous the exercise, the greater the demands of working muscle. If these needs are not met, then exercise will cease (that is, you become exhausted and you won't be able to keep going).

To meet the needs of working muscle, the body has an orchestrated response involving the heart, blood vessels, nervous system, lungs, liver and skin.

Let's examine each need and how it is met by the various systems of the body.

• The muscle cells burn off the ATP (Adenosine triphosphate) they have floating around in about 3 seconds. (Think of this simplistically as sugar)
• The phosphagen system kicks in and supplies energy for 8 to 10 seconds. This would be the major energy system used by the muscles of a 100-meter sprinter or weight lifter, where rapid acceleration, short-duration exercise occurs.
• If exercise continues longer, then the glycogen-lactic acid system kicks in. This would be true for short-distance exercises such as a 200- or 400-meter dash or 100-meter swim.
• Finally, if exercise continues, then aerobic respiration takes over. This would occur in endurance events such as an 800-meter dash, marathon run, rowing and distance skating.

In the first 10 seconds of exercise we'd have used up almost all the easily assessable ATP.

Muscles also have big reserves of a complex carbohydrate called glycogen. A cell splits glycogen into glucose. Then the cell uses anaerobic metabolism (anaerobic means "without oxygen") to make ATP and a byproduct called lactic acid from the glucose.

About 12 chemical reactions take place to make ATP under this process, so it supplies ATP at a slower rate than the phosphagen system. The system can still act rapidly and produce enough ATP to last about 90 seconds. This system does not need oxygen, which is handy because it takes the heart and lungs some time to get their act together. It is also handy because the rapidly contracting muscle squeezes off its own blood vessels, depriving itself of oxygen-rich blood.

There is a definite limit to anerobic respiration because of the lactic acid. The acid is what makes your muscles hurt. Lactic acid builds up in the muscle tissue and causes the fatigue and soreness you feel in your exercising muscles.

Now that you know what is happening it'll help you plan your exercise regimen and gear to best utilize the above systems.

I know this sounds brutal but for people trying to lose weight here also lies the answer for successful weight loss. Longer slower exercise. I've covered this before and will probably do a more detailed post on this later.