Electrophysiologic effects of a therapeutic laser on myofascial trigger spots of rabbit skeletal muscles.
OBJECTIVE
To better understand the mechanisms of therapeutic lasers for treating human myofascial trigger points, we designed a blinded controlled study of the effects of a therapeutic laser on the prevalence of endplate noise (EPN) recorded from the myofascial trigger spot (MTrS) of rabbit skeletal muscle.


METHODS
In eight rabbits, one MTrS in each biceps femoris muscle was irradiated with a 660-nm, continuous-wave, gallium-aluminum-arsenate (GaAlAs) laser, at 9 J/cm2. The contralateral side of muscle was treated with a sham laser. Each rabbit received six treatments. The immediate and cumulative effects were assessed by the prevalence of EPN with electromyographic (EMG) recordings after the first and last treatments.


RESULTS
Compared with pretreatment values, the percentages of EPN prevalence in the experimental side after the first and last treatments were significantly reduced (P < 0.01 for both). The change in EPN prevalence in the experimental side was significantly greater than in the control side immediately after the first and last treatments (P < 0.05). However, no significant differences were noted between the first and last treatments (P > 0.05).


CONCLUSIONS
In our study, immediate and cumulative effects of a GaAlAs laser applied on MTrS were demonstrated on the basis of the assessment of EPN prevalence. It seems that laser irradiation may inhibit the irritability of an MTrS in rabbit skeletal muscle. This effect may be a possible mechanism for myofascial pain relief with laser therapy.
Chen
Kai-Hua
KH
Department of Physical Medicine and Rehabilitation, Chang Gung Memorial Hospital, Chiayi, Taiwan.
Hong
Chang-Zern
CZ
Kuo
Fang-Chuan
FC
Hsu
Hung-Chih
HC
Hsieh
Yueh-Ling
YL
D000818:Animals; D004576:Electromyography; D055724:Electrophysiological Phenomena; D028022:Low-Level Light Therapy; D009045:Motor Endplate / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D009209:Myofascial Pain Syndromes / Q000628:therapy*; D011817:Rabbits; D011897:Random Allocation; D016037:Single-Blind Method