Fitness Column: Fast twitch, slow twitch

The terms fast twitch and slow twitch muscles define the spastic contraction of muscle fibers. If you are an exercise person, the workings of these slow and fast twitch muscles might interest you.

First of all, there are 425 muscles in your body and each one is separated into fibers that look like red threads. The configuration of these fibers, (called Penniform and Unipennate muscles or fibers), have the ability to contract or shorten. There are also Multipennate configurations of muscle fibers that have a smaller range to shorten, but are more powerful.

Now, we get into the fast and slow twitch part. These are two types of muscle fibers used in all categories of sports, weight training, and body building. Fast twitch fibers are activated for short bursts of speed. Examples: sprint for the goal line, 100-yard dash, fast tennis volley, or quick kick for points in soccer. The muscles contract at twice the speed of the slow twitch fibers. They have a high level of internal energy.

Slow twitch fibers are the steady paced type of muscle fiber. They move your muscles at a slower pace, but for longer duration. Examples: the bicyclist, skater, distance runner, and the cross country skier. You are born with a set amount of fast and slow twitch muscle fiber. A muscle biopsy can tell you what level of muscle fiber your body contains. If you are a lean, tall person, you will likely have more fast twitch muscle fiber than the individual with a stocky, heavy boned body.

If you want to work on your already predetermined muscle fiber, you can increase muscle size by hyperplasia or hypertrophy. Hyperplasia increases the muscle size by splitting the fibers. Hypertrophy increases it by thickening the muscle fiber through the use of weight lifting and resistance exercises.

The latter is the most popular form of muscle build up. However, weight lifting can build the slow twitch muscle fiber to a point where it impedes and changes the muscle movement. Then you become "muscle bound" and lose flexibility. A golfers' swing is an example of a needed combination of strength and flexibility. Three types of strength training exercises are used in pre sport work outs. Isometric, Isotonic and Isokenetic exercises.

The proper way to choose a style of strengthening exercise for your sport, is to first find out what type of muscle fiber you have and relate it to the sport you are competing in.

In Isometric exercises, you tighten the muscles without actually changing the length of it. With Isotonic exercises, you change the length of the muscle through part of the complete range while pushing against a resisting force. As in pushing weight, while the load remains constant. This is called Progressive Resistance Exercises. As you get stronger, the resistance increases. Isokenetic exercise is one of constant speed and constant resistance. A good exercise pattern of working with an injured joint or muscle.

The final interesting fact is that coaches all over the country are finding that working with the body's already determined number of fast or slow twitch muscle fiber can greatly increase the capability of their players. Speed exercises develop the fast twitch fibers and slow endurance exercises develop the Slow Twitch fibers.

If you are using weights, be specific. Have your exercise motion duplicate the motion of the sport as closely as possible. Pre conditioning of the fast and slow Twitch muscle fiber will strengthen ligaments and tendons and prevent injury.

Jerry Vance is certified by the American Council on Exercise and teaches fitness at the Carson City Community Center and for the American Lung Association.