Non-Invasive and Quantitative Evaluation for Disuse Muscle Atrophy Caused by Immobilization After Limb Fracture Based on Surface Electromyography Analysis

Background: The clinical evaluation for disuse muscle atrophy usually depends on qualitative rating indicators with subjective judgments of doctors and some invasive measurement methods such as needle electromyography. Surface electromyography, as a non-invasive method, has been widely used in the detection of muscular and neurological diseases in recent years. In this paper, we explore how to evaluate disuse muscle atrophy based on surface electromyography; Methods: Firstly, we conducted rat experiments using hind-limb suspension to create a model of disuse muscle atrophy. Five groups of rats were suspended for 0, 3, 7, 14, and 21 days, respectively. We induced leg electromyography of rats through electrical stimulation and used fluorescence staining to obtain the fiber-type composition of rats' leg muscles. We obtained the best-fitting frequency bands of power spectrum density of surface electromyography for type I and type II fibers in rats' leg muscles by changing the frequency band boundaries. Secondly, we conducted tests on the human body and collected the electromyography of the atrophied muscles of the subjects over a period of 21 days. The changes in muscle fiber composition were evaluated using the frequency bands of power spectrum density obtained from rat experiments. The method was to evaluate the changes in type I fibers by the changes in the area of the best-fitting frequency band of type I fibers and to evaluate the changes in type II fibers by the changes in the area of the best-fitting frequency band of type II fibers. Results: The results of rat experiments showed that type I fibers best fit the frequency band of 20-330 Hz and type II fibers best fit the frequency band of 176-500 Hz. The results of human testing showed that the atrophy of the two types of fibers was consistent with the changes in the areas of the corresponding best-fitting frequency bands. Conclusions: The test results demonstrate the feasibility of using surface electromyography to evaluate muscle fiber-type composition and subsequently assess muscle atrophy. Further research may contribute to the diagnosis and treatment of disuse muscle atrophy.