Unilateral and Immediate Stimulation of Acupuncture Points Xiaohai (SI8) and Jianwaishu (SI14) of the Small Intestine Meridian Increases Electromyographic Activity and Strength in the Ipsilateral and Contralateral Upper Trapezius Muscle.

We previously showed that a yin meridian of the upper limb decreased electromyographic activity (root mean square) and muscle strength ipsilateral and contralateral to the side of stimulation. Here, we tested the upper trapezius (UT) muscle response after stimulation of a yang meridian of the upper limb, the small intestine (SI). Thirty-eight healthy volunteers were randomized into the following groups: UT muscle (SI14), distant of the UT muscle (SI8), without stimulation (CG), and sham (R3). An acupuncturist certificated by the Brazilian Society of Physical Therapists and Acupuncturists performed the needle insertion. Each volunteer received only one stimulation to the right upper limb. The evaluation occurred before, 5 minutes after, and 20 minutes after needle withdrawal. The root mean square activity increased on the right side in the UT muscle for the SI8 and SI14 groups (F = 4.67; p < 0.025) at the 20-minute evaluation. The most vigorous response occurred on the contralateral side because the effects were maintained for 5 minutes after withdrawal (F = 4.52; p < 0.025). Both groups showed an increase in the UT muscle strength at the 20-minute evaluation (F = 3.41; p < 0.025). The CG and R3 groups did not show any changes. Our data indicate that SI a yang meridian increases the UT muscle response.