REM sleep.[2] Muscle tone is regulated by the activity of the motor neurons
and can be affected by various factors, including age, disease, and nerve damage.
Purpose
If a sudden
flexor
muscles are involved in the maintenance of a constant tone while at rest. In skeletal muscles, this helps maintain a normal posture.
Resting muscle tone varies along a
bell-shaped curve
. Low tone is perceived as "lax, flabby, floppy, mushy, dead weight" and high tone is perceived as "tight, light, strong". Muscles with high tone are not necessarily strong and muscles with low tone are not necessarily weak. In general, low tone does increase flexibility and decrease strength, and high tone does decrease flexibility and increase strength, but with many exceptions. A person with low tone will most likely not be able to engage in "explosive" movement such as needed in a sprinter or high jumper. These athletes usually have high tone that is within normal limits. A person with high tone will usually not be flexible in activities such as dance and yoga. Joint laxity contributes greatly to flexibility, especially with flexibility in one or a few areas, instead of overall flexibility.
For example, a person can be high tone with normal to poor flexibility in most areas, but be able to put the palms of the hands on the floor with straight knees due to hypermobile sacroiliac joints.[citation needed] It is important to assess several areas before deciding if a person has high, low, or normal muscle tone. A fairly reliable assessment item is how the person feels when picked up.[citation needed] For example, small children with low tone can feel heavy while larger, high tone children feel light, which corresponds with the description of "dead weight".[citation needed]
Pathological tonus
Physical disorders can result in abnormally low (
rigidity is velocity-independent resistance to passive stretch (i.e. there is uniform increased tone whether the elbow is passively moved quickly or slowly).[1]
Spasticity can be in the form of the clasp-knife response, in which there is increased resistance only at the beginning or at the end of the movement. Rigidity can be of the leadpipe type, in which there is resistance throughout to passive movement, or it may be of cogwheel type, in which the resistance to passive movement is in a jerky manner.
Normally, people are unaware of their muscle tone in their daily activities. The body maintains the balance between the tone of flexor and extensor muscle groups. Sometimes, in normal, healthy people, that tone is lost either in flexors or extensor muscle groups in isolation, temporarily and intermittently resulting in "muscle cramps". Treating these extensor or flexor group of muscles in isolation can be difficult. Generally,
can help with cramps and is warranted when they become troublesome. But these medication cause their relaxing effect in both groups by moderating their tone. The cause of disproportionate intermittent contractions of either flexors or extensors or the cause of cramps is unknown. The stimulus for these "cramps" may originate in the cerebral cortex, the spinal cord, or the muscle itself. This could indicate developing pathology or other problems in the future.
^ abcO’Sullivan, S. B. (2007). Examination of motor function: Motor control and motor learning. In S. B. O’Sullivan, & T. J. Schmitz (Eds), Physical rehabilitation (5th ed.) (pp. 233-234). Philadelphia, Pennsylvania: F. A. Davis Company.
