Surface electromyography and joint angle kinematics of horses at walk and trot on a treadmill

This study aimed to evaluate electromyographic and kinematic parameters of the thoracic and pelvic limbs of horses at a walk and trot on a treadmill. Eleven Brazilian Sport Horses trained for Eventing were assessed in a completely randomized design under two conditions: walk (1.8 m/s) and trot (3.6 m/s). Horses were evaluated on a high-speed treadmill using surface electromyography (sEMG) and kinematic analysis. sEMG was performed bilaterally on the mm. extensor carpi radialis and mm. flexor carpi ulnaris; bilateral muscles of the pelvic limb: mm. tensor fascia latae and mm. biceps femoris using disposable bipolar surface electrodes connected to Miotool Fisio® equipment, with data processed in Miotec Suite 1.0 software. Kinematic analysis of the carpal, coxofemoral, and femorotibiopatellar joints was performed using a GoPro camera and KINOVEA software. The extensor carpi radialis showed greater activation during forelimb extension at walk, contributing to limb stabilization, while at trot its role became predominantly stabilizing. The flexor carpi ulnaris was active during carpal flexion at walk and showed greater stabilization-related activity at trot. In the pelvic limb, the tensor fascia latae stabilized and flexed the femorotibiopatellar joint at walk, but contributed mainly to coxofemoral extension at trot, indicating a functional transition between gaits. The biceps femoris contributed to stabilization and propulsion, especially during the stance phase at trot, with increased activity during coxofemoral extension. In conclusion, trotting promoted greater muscle recruitment and more dynamic muscular behavior due to increased biomechanical demand and limb stabilization requirements.