Electromyographic and Strength Analyses of Activation Patterns of the Wrist Flexor Muscles after Acupuncture

This study analyzed the electromyographic and strength responses of the flexor muscles of the wrist following stimulation of acupuncture points. A total of 52 participants were randomly divided into four groups: local (heart 3, HT3), distant (heart 4, HT4), control (bladder 60, BL60), and naïve control groups. To obtain the root mean square electromyographic activity, we placed surface electrodes over the wrist flexors. To obtain kilogram force (kgf) values, we attached a force transducer to the floor and to the hands of participants. Both values were recorded over three repetitions of maximal isometric wrist flexion contractions. Data were analyzed using one-way analyses of variance, followed by Dunnett's post-hoc tests. We found reductions in electromyographic activity contralateral to the stimulated point in the distant group 10 minutes after removal of the needles (F(3,48) = 3.25; p < 0.05). Regarding muscle strength, ipsilateral and contralateral stimulation in the distant group produced kgf levels prior to and 10 minute and 20 minutes after withdrawal of the acupuncture needle that were lower than that obtained prior to insertion of the needle (F(3,48) = 5.82; p < 0.05). Thus, stimulation of the acupuncture points distant from the wrist flexors reduced ipsilateral and contralateral muscle strength and decreased the root mean square values contralateral to the site of stimulation.