An in vivo equine forelimb model for short-term recording of peak isometric force in the superficial and deep digital flexor muscles.
Authors: Zarucco Laura, Swanstrom Michael D, Driessen Bernd, Hawkins David, Hubbard Mont, Steffey Eugene P, Stover Susan M
Journal: Veterinary surgery : VS
Summary
# Editorial Summary Researchers at UC Davis developed an experimental model to measure the peak isometric force capacity of the superficial and deep digital flexor muscles in living horses, addressing a significant gap in our understanding of these functionally critical structures. Using four anaesthetised Thoroughbreds, they fixed the forelimb in a rigid frame, isolated and clamped each flexor tendon at its myotendinous junction, and stimulated the median and ulnar nerves at varying voltages whilst recording contractile force through a load cell. Peak isometric forces averaged 716 ± 192 N for the superficial digital flexor and 1,577 ± 203 N for the deep digital flexor when both nerves were stimulated supramaximally at 2.5–5.0 V and 50 Hz; interestingly, median nerve stimulation dominated force production in the deep flexor whilst ulnar stimulation was more influential in the superficial flexor. For farriers, physiotherapists and veterinarians managing flexor tendon injuries, contractures and performance-related lameness, this foundational biomechanical data provides objective reference values for normal muscle function and opens pathways to evaluate how pathology, rehabilitation and therapeutic interventions alter force-generating capacity—ultimately informing more targeted treatment strategies for these prevalent conditions.
Read the full abstract on PubMed
Practical Takeaways
- •This model provides quantitative baseline data on digital flexor muscle force capacity that can inform treatment planning for flexor tendon injuries and deformities
- •The differential innervation patterns of SDF and DDF muscles may help explain functional differences in flexor anatomy and should be considered when evaluating flexor injuries
- •Understanding peak isometric forces in these muscles provides a foundation for developing more targeted therapeutic interventions for common flexor pathologies
Key Findings
- •Peak isometric force for SDF muscle was 716 ± 192 N and for DDF muscle was 1,577 ± 203 N under supramaximal dual nerve stimulation
- •Combined median and ulnar nerve stimulation produced greater normalized force than single nerve stimulation at voltages >1 V for both muscles
- •Median nerve stimulation produced greater force in DDF muscle while ulnar nerve stimulation produced greater force in SDF muscle
- •Stimulation voltage of 2.5–5.0 V at 50 Hz achieved maximal muscle contraction for both flexor muscles