OBJECTIVE: Dry needling of myofascial trigger points can relieve myofascial pain if local twitch responses are elicited during needling. Spontaneous electrical activity (SEA) recorded from an active locus in a myofascial trigger point region has been used to assess the myofascial trigger point sensitivity. This study was to investigate the effect of dry needling on SEA.

DESIGN: Nine adult New Zealand rabbits were studied. Dry needling with rapid insertion into multiple sites within the myofascial trigger spot region was performed to the biceps femoris muscle to elicit sufficient local twitch responses. Very slow needle insertion with minimal local twitch response elicitation was conducted to the other biceps femoris muscle for the control study. SEA was recorded from 15 different active loci of the myofascial trigger spot before and immediately after treatment for both sides. The raw data of 1-sec SEA were rectified and integrated to calculate the average integrated value of SEA.

RESULTS: Seven of nine rabbits demonstrated significantly lower normalized average integrated value of SEA in the treatment side compared with the control side (P less tham 0.05). The results of two-way analysis of variance show that the mean of the normalized average integrated value of SEA in the treatment group (0.565 +/- 0.113) is significantly (P less than 0.05) lower than that of the control (0.983 +/- 0.121).

CONCLUSIONS: Dry needling of the myofascial trigger spot is effective in diminishing SEA if local twitch responses are elicited. The local twitch response elicitation, other than trauma effects of needling, seems to be the primary inhibitory factor on SEA during dry needling.