1.2.1 - How Muscles Contract (Stretching)
Description
This article is from the Stretching FAQ, by Brad Appleton Brad_Appleton@ivhs.mot.com with numerous contributions by others.
1.2.1 - How Muscles Contract (Stretching)
The way in which all these various levels of the muscle operate is as
follows: Nerves connect the spinal column to the muscle. The place where
the nerve and muscle meet is called the "neuromuscular junction". When an
electrical signal crosses the neuromuscular junction, it is transmitted
deep inside the muscle fibers. Inside the muscle fibers, the signal
stimulates the flow of calcium which causes the thick and thin myofilaments
to slide across one another. When this occurs, it causes the sarcomere to
shorten, which generates force. When billions of sarcomeres in the muscle
shorten all at once it results in a contraction of the entire muscle fiber.
When a muscle fiber contracts, it contracts completely. There is no such
thing as a partially contracted muscle fiber. Muscle fibers are unable to
vary the intensity of their contraction relative to the load against which
they are acting. If this is so, then how does the force of a muscle
contraction vary in strength from strong to weak? What happens is that
more muscle fibers are recruited, as they are needed, to perform the job at
hand. The more muscle fibers that are recruited by the central nervous
system, the stronger the force generated by the muscular contraction.
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