Functional Electrical Stimulation for Equine Muscle Hypertonicity: Histological Changes in Mitochondrial Density and Distribution

Abstract Functional electrical stimulation (FES) has proven to be advantageous in reducing muscle hypertonicity and reeducating muscle memory in the human population and has recently been used in horses. Six horses ranging in age from 10 to 17 years were selected for the study. Still photographs and clinical evaluations using the Modified Ashworth Scale to characterize muscle hypertonicity were performed on all horses pre- and post-FES. Functional electrical stimulation treatments were performed over a period of 8 weeks, resulting in a total of 22 treatments per horse. Biopsies pre- and post-FES treatments were obtained from the longissimus lumborum muscle of each horse. Mitochondrial density and distribution of the blinded samples pre- and post-FES were determined, and a two-sided Welch's t test was used to analyze the results. The results of the clinical evaluations and of morphometric analyses comparing pre- to post-FES muscle biopsies found: (1) a significant increase ( P P P