Changes in muscular strength and electromyogram in rats with muscular disuse atrophy following electrical stimulation

摘要

BACKGROUND: Atrophy of skeletal muscle is found under the condition of muscular disuse or in the process of fixation. It is affected by fixation, and electromyogram (EMG) discharge and muscular strength levels will be significantly decreased with accelerating tendency. Electrical stimulation (ES) therapy can release the velocity of muscular disuse atrophy effectively, so it is an effective method for preventing and treating muscular disuse atrophy and accelerating rehabilitation velocity following removal of fixation.OBJECTIVE: To observe the effect of ES therapy at different time points following the fixation of rat models of muscular disuse atrophy on muscular strength and EMG of quadriceps femoris.DESIGN: A randomized and controlled animal experiment.SETTING: Department of Rehabilitation and Physiotherapy, Guangzhou General Hospital of Guangzhou Military Area Command of Chinese PLA; College of Sports Science, South China Normal University.MATERIALS: Male SD rats, of clean grade, aged 4 months old, weighing (230±10) g, were provided by the Animal Experimental Center of Sun Yat-sen University. EMG measurement and analysis system (NEC Company, Japan) and four-channel recorder (NEC Company, Japan) were used in this experiment.METHODS: This experiment was carried out in the Laboratory of Human Sports Science, South China Normal University between September 2003 and March 2004. Totally 125 successful SD rat models of muscular disuse atrophy were randomly divided into 5 groups with 25 rats in each by a lot: normal control group, in which, the rats were untouched; ES 24 hours, 1, 2 and 3 weeks groups: the knees of rats in these four groups were fixed. Rats in four groups underwent ES therapy at 24 hours, 1, 2 and 3 weeks after fixation. T90- Ⅱ computer ES muscular strength training instrument was used in ES therapy every other day. The instrument was set as square wave,5 mA current intensity and 10 minutes a day. Muscular strength of quadriceps femoris and data of EMG were collected before and at the end of 1, 2, 3 and 4 weeks after fixation, separately.MAIN OUTCOME MEASURES: EMG discharge level and muscular strength levels of quadriceps femoris of rats at different time points.RESULTS: Totally 125 rats were involved in the final analysis. ①There were no obvious changes in discharge level of EMG within 4 weeks in normal control group; Discharge level of EMG of the other groups was significantly decreased from the 2nd week to the 4th week, and that of ES 24 hours, 1, 2 and 3 weeks was decreased by 21.26%, 34.65%, 45.67% and 55.12% respectively as compared with normal control group. The earlier the ES therapy was conducted, the smaller the decreasing amplitude was. ② There were no obvious changes in muscular strength within 4 weeks in normal control group; Muscular strength change was significantly decreased from the 2nd week to the 4th week, and that of ES 24 hours, 1,2 and 3 weeks was decreased by 28.97%, 53.10%, 61.38% and 66.90%, respectively as compared with normal control group. The earlier the ES therapy was conducted, the smaller the decreasing amplitude was.CONCLUSION: ES can effectively release the decreasing velocity of muscular strength and EMG of rats with muscular disuse atrophy. The earlier ES therapy following fixation indicates smaller decreasing amplitude of muscular strength.