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The Balance of Muscle

Questions to ponder
• Why is the third set of the same exercise with the same weight harder than the first?

Definitions
Muscle: number of muscle fibers bound together by connective; Cardiac, Smooth and Skeletal

Muscle Fiber: muscle cell

Motor Unit: A single motor neuron and the muscle cells it innervates

Muscle Fatigue: decrease in muscle tension with prolonged activity

Connective Tissue: elements that connect, anchor and support body structures

Skeletal Muscle Structure

Sarcomere-the basic contractile unit

Each motor unit contains all of the same type of type of fibers. All skeletal muscles have a ratio of fast to slow
twitch fibers.  This ratio helps to define the primary use of the muscle and is genetically predisposed, but
appropriate training can alter the ratio. This ratio also changes as we age by decreasing the number of fast
twitch fibers.


Fast and Slow Twitch Muscles                  Fast Twitch                                     Slow Twitch
Purpose:                                     Produce Power,  faster and stronger          Repeat contractions

Recruitment:                                                    Last                                                       First

Adaptation to training:                                Hypertrophy                                     Increase capillaries,
                                                                                                               Increase in ability to produce energy