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Balance is a partly involuntary and unconscious business, dependent on "spinal reflexes." When provided with appropriate context, these reflexes go into oscillation that is called "clonus," a phenomenon that is familiar to everybody and which is easily produced. (While sitting, place the leg with thigh horizontal and foot supported on the floor.
The stretch reflex (myotatic reflex), or more accurately "muscle stretch reflex", is a muscle contraction in response to stretching a muscle. The function of the reflex is generally thought to be maintaining the muscle at a constant length but the response is often coordinated across multiple muscles and even joints. [ 1 ]
The body varies the stiffness of its limbs by three primary mechanisms: muscle cocontraction, [1] [8] [9] posture selection, [6] and through stretch reflexes. [ 1 ] [ 10 ] [ 11 ] [ 12 ] Muscle cocontraction (similar to muscle tone ) is able to vary the stiffness of a joint by the action of antagonistic muscles acting on the joint.
A cramp is a sudden, involuntary, painful skeletal muscle contraction [1] [2] or overshortening associated with electrical activity; [3] while generally temporary and non-damaging, they can cause significant pain and a paralysis-like immobility of the affected muscle.
Young adults in the U.S. reportedly sit about nine to 10 hours a day, compared to older adults, who sit up to 13 hours a day. And a lot of us know that sitting for long periods of time can be harmful.
A fasciculation, or muscle twitch, is a spontaneous, involuntary muscle contraction and relaxation, involving fine muscle fibers. [1] They are common, with as many as 70% of people experiencing them. [1]
In a busy world, is stretching really necessary? Here's what experts say.
Chronic toe walking leads to muscle contracture due to the lack of calf muscles being adequately stretched. Once the muscle contracture has developed, the voluntary toe walking then becomes involuntary. [2] If someone has a disability that causes spasticity (such as cerebral palsy), they may walk on their toes involuntarily.