Muscular endurance is a health-related component of physical fitness. It is the ability of a skeletal muscle or group of muscles to continue contracting over a long period. When you have good muscular endurance you have the ability to resist fatigue while holding a position, carrying something for a long period of time, or repeating a movement without getting tired. As you train for muscular endurance, the muscles adapt as a result of changes in the slow-twitch fibers. The slow twitch fibres have a high capacity to use oxygen. They are called red fibres due to the large amount of blood supply found in them. They are slow to contract but have the ability to continue to contract over long periods of time.

Lifting heavy weights with low repetitions will develop strength. Dynamic muscular endurance is the opposite. You must do higher numbers of repetitions and with lower resistance. Dynamic muscle endurance is the muscle's ability to contract and relax repeatedly. An example of an exercise requiring dynamic endurance is the push-up. At some point, the muscles will become fatigued, and you will no longer be able to perform them. Examples of everyday activities requiring dynamic endurance are carrying groceries to your car, raking your yard, and playing several sets of tennis. Each of these activities requires some muscular strength, but they also require the muscle to repeat the movement over a period of time.

A muscle's ability to remain contracted for a long period of time is called static muscle endurance. It is usually measured by the length of time you can hold a body position. For example using the pushup, if we measure the length of time a person can remain in the flexed arm position, we are measuring static endurance. This means lowering the body in the pushup position until the arms are in a ninety-degree angle parallel to the floor and holding this position as long as possible. Some activities requiring static endurance include handstands and standing in line for hours for concert tickets or rides at the midway.

There are a wide variety of effective programs for developing muscular endurance. One of the most popular methods is circuit resistance training. This training takes place by moving from one station to the next, usually set up in a circle. At each station a different exercise is performed with high repetitions but low to moderate resistance. Fifteen seconds of rest is provided while changing stations. Approximately ten exercise stations are used, and the exerciser repeats the circuit two to three times.

Many people are interested in endurance exercises because they can take inches off of body measurements. Usually some strengthening and some changes in body contour occur. Also, endurance exercises speed up metabolism, and your body burns calories at a higher rate for several hours after the endurance exercise.

Cardiovascular endurance depends upon the efficiency of the heart muscle, circulatory system and respiratory system. Muscular endurance depends on the efficiency of the skeletal muscles and the nerves that control them. You can train for cardiovascular endurance by running, but if the leg muscles lack the muscular endurance to continue for more than a few minutes, you will not be able to run long enough to develop cardiovascular endurance.

It is also important to remember that the training program for muscular endurance should resemble the activity for which the endurance is needed. Performing muscular endurance exercises withupper body muscles will not help improve the endurance of the leg muscles. Probably the best training program is performing the sport skill repeatedly.

Women in Motion September 2001