Comparison of Local Twitch Responses Elicited by Palpitation and Needling of Myofascial Trigger Points

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Abstract
Objectives: To compare local twitch responses [LTRs] that are produced by manual snapping palpation to those produced by needle penetration of myofascial trigger points [TrPs]. Methods: One hundred and five LTRs were recorded electromyographically from 13 TrPs in 13 muscles and 9 subjects. Sixty-four LTRs were elicited by snapping palpation and forty-one by subsequently inserting a monopolar electromyographic [EMG] probe needle repeatedly into the same TrP region. The electrical activity of an LTR was recorded from a response EMG needle inserted 4 cm from the TrP in the same palpable taut band and with snapping palpation also from a surface electrode overlying the response needle electrode. Results: The EMG characteristics of the LTRs elicited by needle insertion and those elicited by snapping palpation were not significantly different in the mean number of discharges per LTR, mean duration, or discharge density. Conclusions: At the level of detail examined in this study, no indication of a difference was found between LTRs elicited by needle insertion and those elicited by snapping palpation. The results of this study are consistent with previous observations that an LTR occurs specifically in the fibers of a taut band.