Effect of unilateral electro-acupuncture on function of ipsilateral and contralateral tibialis anterior muscle

AIMS: It is known that unilateral resistance exercise or electromyostimulation training can increase muscular strength not only in the trained limb, but also in the homologous muscle of the contralateral limb. The principle of using unilateral therapy to treat conditions of the contralateral limb has been previously applied in traditional Chinese medicine. The primary aim of this study was to investigate whether unilateral electro-acupuncture would alter muscle strength in the treated and the contralateral limb. A secondary aim was to validate a statistical model for assessment of EMG-force relationship in response to the training. METHODS: Sixty college-aged healthy male subjects were randomly allocated into four groups: electro-acupuncture (EA), resistance training (RT), combined EA and RT (ER), and control (CG). Subjects in the experimental groups trained the right tibialis anterior muscle in dorsiflexion exercise three sessions per week for 4 weeks. In EA, electro-acupuncture was delivered to the acupoints of Zusanli and Xiajuxu, which are located on the muscle belly of tibialis anterior, for ~15min, with gradually increased pulse frequency of 20-40Hz and intensity of 10-40V. The RT performed eccentric dorsiflexion at 30deg/sec on Cybex dynamometer for ~15min, with progressively increased 3-5 sets of 3-5 contractions. The ER combined protocols of RT and EA in each session. The CG kept normal daily activities without training. The dorsiflexion strength was measured in isokinetic, isometric, and isotonic tests, and surface EMG was recorded in the isometric and isotonic tests, before and after the training period. A three-way repeated measures ANOVA was performed to examine the interactions between groups, training, and limbs. Mean EMG amplitude of ~3s period was obtained from each contraction. Natural logarithm transformation was perform on EMG data to normalise distribution, before EMG-force relationship was analysed using MLwiN program. Mixed models were fitted with two levels of random variation. Residual maximum likelihood estimates were obtained, while nested models were compared using the -2loglikelihood statistics from maximum likelihood (ML) fits. RESULTS: Strength of the trained limb improved significantly (P