Unfortunately, I'm not sure there is a single definition that is widely accepted. To best explain this, I'll leave with you with the following excerpt from Davidoff (1992, Neurology).
"The term “muscle tone” has been used imprecisely in neurologic literature, in large measure because it is defined so differently by the neurologic clinician and by the experimental neurophysiologist. Neurologists define muscle tone in an operational manner as the resistance to movement when the patient is in a state of voluntary relaxation. In other words, the neurologist forms a qualitative assessment of the magnitude of the resistance to passive flexion and extension of the joints in a limb, or observes how a limb responds to being shaken or to being released suddenly. At best, this is an imprecise process, for there is little correlation between clinical judgments of muscle tone and quantitative mechanical measurements of resistance to passive limb movement.
Although nothing in the definition provided by neurologists stipulates that the resistance to passive stretch is determined by reflex contractions of muscle, most clinical authorities have tacitly assumed that muscle tone can be equated with the reflex tone described by Sherrington in animals with extensive central lesions. Sherrington, who was the first to subject stretch reflexes to physiologic
analysis, showed that the exaggerated tone in the extensor muscles of cats with decerebrate rigidity was indeed reflexly mandated: it disappeared after dorsal root section."
...
"In contrast, physiology texts have ordinarily contended that muscle tone is a state of tension, or a degree of constant steady contraction of muscle. According to this line of thought, spinal monosynaptic stretch reflexes, with contributions from neck and labyrinthine reflexes, determine muscle tone. Such tonic activity is present mainly in antigravity muscles and is responsible for the maintenance of posture. Thus, although their perspectives are very different, both clinicians and physiologists have traditionally implicated spinal segmental stretch reflexes as the major determinant of muscle tone."
http://www.ncbi.nlm.nih.gov/pubmed/?term=1579249
Also, depending on what you're looking for, "hypertonia", "hypotonia", and "spasticity" would make good search terms (in addition to "muscle tone").
Clonus and Dystonia are also highly related.
Mr Hambly, here are my insights in relation to your question.
According to Professor Arved Vain, who is the inventor of Myoton devices (http://www.myoton.ee/en), muscle tone can be explained like this:
Muscle tone may be defined as the mechanical tension in the muscle, which ensures the balance of the body, the relative position of the body parts or the posture, and creates a pretension for muscular work; where the tone of the entire neuromuscular unit is created on one hand by the central nervous system, on the other hand, through muscle cell tone (The Oxford English Dictionary, 1991, Stedman's Medical Dictionary, 1995; THEWS et al 1980).
Muscle tone is not strictly a mechanical property but a state of tension. Non-neural tone (state of resting tension or the muscle’s resistance to passive stretch during resting state) is represented by frequency of oscillation (Hz).
Muscle tone in short is the intrinsic tension.
“The Oxford English Dictionary” (1991), Second Edition. Vol XVIII, Clarendon
Press, Oxford.
“Stedman’s Medical Dictionary” (1995), Williams&Wilkins, Baltimore, 643.
Thews G., Mutschler E, Vaupel P. (1980), “Anatomie,Physiologie, Pathophysiologie
des Menschen. Ein Lehrbuch für Pharmazeuten und Biologen.”, - Wissenschaftliche
Verlagsgesellschaft MBH Stuttgart.
Also, this might help:
http://www.sciencedirect.com/science/article/pii/S1360859208000922?via=ihub#
Muscle tone, as mentioned earlier, is a horribly imprecise term. And confusingly it means a variety of things depending on who is discussing the term. I think that until we can agree somewhat on a definition and crucially a way to measure it we will continue to have this confusion.
I agree with Jonathan, there are many factors to consider and therefore one single definition does not apply.
Unfortunately, there is no single definition to muscle tone. In addition to the definitions provided above, you can also define muscle tone as:
(1) The muscle in a steady partially contracted state caused by the successive flow of nerve impulses.
(2) The amount of tension or resistance to movement in a muscle.
The subjective definition of muscle tone is also dependent on the muscle in question (postural muscles vs non-postural muscles as an example)
Sorry couldn't be of more help
I think a useful and an old definition is that muscle tone is resistance to passive stretch in in situ muscle. The reference below is a short article I wrote in JPhysiol, if interested (see first para copied below) .
"It is generally well known that upper motor neuron lesion, as may occur after a stroke, leads to impairment of voluntary muscle function and development of increased tone or spasticity in the affected skeletal muscles. The increased muscle tone, or resistance to passive stretch, is at least initially caused by exaggerated stretch reflexes (Buller, 1957; Crenna, 1998). More recent findings, however, have indicated ................................................
(Ref)
J Physiol 589.11 (2011) p 2665 2665, PERSPECTIVES
Skeletal muscle stiffness and contracture in children with spastic cerebral palsy
Regards,
KW
- Badges
- Science topic
- Similar topics
- Correction