Functional electrical stimulation as a safe and effective treatment for equine epaxial muscle spasms: Clinical evaluations and histochemical morphometry of mitochondria in muscle biopsies
Authors: Ravara Barbara, Gobbo Valerio, Carraro Ugo, Gelbmann Lin, Pribyl Jamie, Schils Sheila
Journal: European Journal of Translational Myology
Summary
Functional electrical stimulation (FES) has demonstrated clinical efficacy in treating epaxial muscle spasms in horses, a condition characterised by reduced pelvic extension and impaired movement, particularly in retired dressage horses. Six horses aged 10–17 years received FES treatment to the sacral/lumbar region three times weekly for eight weeks (22 treatments total), with muscle function assessed using the Modified Ashworth Scale and pre- and post-treatment biopsies from the longissimus lumborum examined histochemically for fibre morphology and mitochondrial density. Clinical evaluation revealed a one-grade improvement on the spasm scale after approximately four treatments, with palpation confirming reduced epaxial spasming; whilst only limited hypertrophy occurred in muscle fibres themselves, post-FES biopsies showed increased mitochondrial density and distribution, suggesting enhanced oxidative capacity rather than gross structural changes. Importantly, no evidence emerged of FES-induced muscle damage—denervated fibres identified in post-treatment samples were present pre-treatment or consistent with age-related neuropathy rather than iatrogenic injury. For equine practitioners managing chronic epaxial dysfunction in older horses, FES offers a non-invasive intervention that safely improves functional movement, likely through enhanced muscle perfusion and metabolic capacity rather than simple hypertrophy, making it particularly valuable where traditional rehabilitation may be limited.
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Practical Takeaways
- •FES applied 3 times weekly to the sacral/lumbar region can effectively reduce epaxial muscle spasms in horses with clinical improvements evident within 4 treatments
- •FES appears to work by enhancing muscle contraction and blood flow rather than building muscle mass, making it suitable for older or compromised horses
- •FES is a safe rehabilitation tool for horses with epaxial dysfunction; monitor for pre-existing denervation but do not expect significant muscle hypertrophy from this protocol
Key Findings
- •All six horses showed one-grade improvement on Modified Ashworth Scale after approximately four FES treatments over 8 weeks
- •Clinical palpation confirmed reduced epaxial muscle spasms and improved sacral/lumbar functional movement following FES
- •Muscle biopsies showed increased mitochondrial density and distribution post-FES, suggesting improved muscle perfusion and oxidative capacity
- •FES treatment was safe with no evidence of generalized muscle fiber damage; denervated fibers present pre-treatment were also present post-treatment