One of the aspects that keeps dogging the ‘Myofascial Pain Syndrome’ world are inaccuracies; This extends to how we use terms to explain what is observed and ultimately treated.

Recently, I came across a study by Rha et al. that defined a local twitch response  (LTR) as:

…a momentary contraction (fasciculation) of the taut band in response to mechanical stimulation.

This study does not deal with issues of nomenclature, but it serves purely as an example for the terminology issue.

As is illustrated in the table below, both a muscle twitch and fasciculation are forms of muscle contraction. However, whereas some form of stimulation is required to elicit a twitch, a fasciculation occurs spontaneously.

Technically then, we should distinguish between two types of LTR, one that occurs spontaneously (Type I) and one, which occurs during/after mechanical stimulation (type II). In this way, a muscle physiologist, for example, would be able to follow the adaption of basic terms in this context.

At this point the distinction may seem, as semantics, however, who knows what clinically relevant differences may exist?

Common use terminology and an adaptation of the Local Twitch Response definition.

[custom_table style=”1″]

Type Description
Contraction Increase in skeletal muscle tension- may or may not result in muscle shortening.
Twitch A brief contractile response of a skeletal muscle elicited by a single, maximal volley of impulses in the motor neuron supplying it.
Fasciculation A small, local contraction of muscle, visible through the skin, representing a spontaneous discharge of a number of fibres innervated by a single motor nerve filament
Local Twitch Response –Type I A momentary contraction of a taut band in response to mechanical stimulation
Local Twitch Response- Type II A spontaneous momentary contraction of a taut band.



Detecting Local Twitch Responses of Myofascial Trigger Points in the Lower-Back Muscles Using Ultrasonography. Dong-wook Rha, MD, PhD, Ji Cheol Shin, MD, PhD, Yong-Kyun Kim, MD, PhD, Jae Hwan Jung, MD, Young Uhk Kim, MD, Sang Chul Lee, MD, PhD. Arch Phys Med Rehabil Vol 92, October 2011.