Endurance
Endurance is the ability of a muscle to work over a period
of time. Muscles need a steady supply of oxygen and nutrients to function
and as the muscle tires, it looses its supplies of nutrients and the ability to
respond. Specific training can increase the body's ability to use it's
supply of oxygen and its stores of nutrients more efficiently.
For runners, greater endurance means longer periods of
work at maximum function. It also means using the muscles to their
depletion of stored nutrients. For precision sports such as baseball and
tennis, it means an increase of accuracy and speed. A fatigued muscle
lacking adequate oxygen and nutrients is slow to respond to nerve signals.
Muscular endurance depends on:
- Availability of nutrients- the fuel muscles burn to
produce ATP (energy) is glycogen which is a type of sugar that is stored in
the muscles. The amount present at the time of exercise comes from
what was eaten approximately 12 hours earlier. When muscles are
depleted they become heavy and unresponsive. This is often called
"hitting the wall" or "bonking". The storage of
sugar can be increased by depleting the store and then loading up on
carbohydrates. Repeatedly exercising to depletion can cause more
nutrients to be stored during the recovery and rest periods which will
increase performance.
- Availability of oxygen which is necessary to burn the
muscle sugar and complete the metabolic process. Good aerobic fitness
can help ensure an adequate supply of oxygen.
- Proper removal of wastes that build up in the muscle
and inhibits proper contraction is also necessary. There is much
controversy over the theory of lactic acid building up in a muscle and the
recovery time. (see
Lactating Mythers Massage and the Lactic Acid Myth Keith Eric Grant, Ph.D.)
-
Thermal control. The build up of heat reduces the
muscle response and tissue damage. Cramps may also be a result of
overheating of the muscle (although there are also other reasons for
cramping). Muscles cannot function properly unless they are adequately
cooled.
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