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Muscle injury (such as a large burn or surgery) can cause muscle contractures as internal scar tissue (adhesions and fibrosis) develops. Repetitive muscle injuries (e.g. sports injuries, major muscle strains) and micro-injuries (e.g. overuse injuries, minor muscle strains) can also cause this. Adhesions and fibrosis are made of dense fibrous ...
All movements, e.g. touching your nose, require motor neurons to fire action potentials that results in contraction of muscles. In humans, ~150,000 motor neurons control the contraction of ~600 muscles. To produce movements, a subset of 600 muscles must contract in a temporally precise pattern to produce the right force at the right time. [6]
In that study, an increase in muscle fiber conduction velocity was observed when there was a higher level of voluntary muscle contraction, which agrees with the gradual recruitment of higher-force muscle types. [16] In Wistar rats, it was found that cell size is the crucial property in determining neuronal recruitment. [17]
Depiction of smooth muscle contraction. Muscle contraction is the activation of tension-generating sites within muscle cells. [1] [2] In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as when holding something heavy in the same position. [1]
Reciprocal inhibition is a neuromuscular process in which muscles on one side of a joint relax to allow the contraction of muscles on the opposite side, enabling smooth and coordinated movement. [1] This concept, introduced by Charles Sherrington, a pioneering neuroscientist, is also referred to as reflexive antagonism in some allied health fields.
When necessary, the maximal number of motor units in a muscle can be recruited simultaneously, producing the maximum force of contraction for that muscle, but this cannot last for very long because of the energy requirements to sustain the contraction. To prevent complete muscle fatigue, motor units are generally not all simultaneously active ...
In pathology, a contracture is a shortening of muscles, tendons, skin, and nearby soft tissues that causes the joints to shorten and become very stiff, preventing normal movement. [ 1 ] [ 2 ] A contracture is usually permanent, but less commonly can be temporary (such as in McArdle disease ), [ 3 ] or resolve over time but reoccur later in life ...
An induction shock produces a contraction or fails to do so according to its strength; if it does so at all, it produces the greatest contraction that can be produced by any strength of stimulus in the condition of the muscle at the time. This principle was later found to be present in skeletal muscle by Keith Lucas in 1909. [1]