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The fast twitch fibers..
Tue Dec 1, 2015 14:43
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The fast twitch muscle fibers are responsible for giving the athlete his speed, agility, quickness, and power. Fast twitch fibers are up to 10 times faster than slow fibers.

In most muscles, these fibers are intermingled. However, there is usually a predominance of one or the other. For example, in postural muscles of the spine, the slow twitch fibers dominate. This is because slow twitch fibers can undergo extensive repetitive contractions without fatigue.

In non-postural limb muscles like the arms and legs, the fast twitch fibers dominate. This allows for powerful forces to be generated over a short period of time.

Because the fibers are intermingled it is not possible to isolate out a single fiber type during a muscular contraction. All of the fibers contract together, though at times one of the fibers may be dominant during the contraction.

All of these fiber types are arranged into groups known as motor units. A motor unit is defined as one motor neuron and all the muscle fibers it supplies. There are many motor units within the overall muscle. When a muscle begins to contract, an action potential is carried down the motor neuron across the motor endplate to the muscle fibers it supplies.

Initially, only some of the motor units become active. As the demand on the muscle increases, more and more motor units are recruited to help support this demand. As the demand on the muscle decreases, the number of motor units also decreases. This is a general description of muscular contraction.

With isometric training, a muscle opposes some form of resistance and is contracted to a certain length and then held for a certain period of time, usually 10 seconds or more. There are no repetitions required here as in weight training.

The biggest advantage to this type of training is twofold. First, by forcing your muscles to hold a position for a certain length of time, your body starts to recruit more and more motor units to help maintain this contraction. Motor units that are rarely exercised within a muscle are now brought into use, perhaps for the first time.

Second, the motor units that are recruited are forced to contract continuously, time after time, until your muscles achieve a state of maximum intensity safely and effectively.

The end result is that the entire muscle matures very quickly.

Resistance band training with an isometric strategy adds additional benefits to the athlete beyond traditional isometrics.

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