Surface electromyography (sEMG) of equine core muscles and kinematics of lumbo-sacral joint during core strengthening exercises

Dynamic Mobilisation Exercises (DME) and myotatic reflex exercises were developed with the aim of improving core strengthening in horses. Previous studies have shown DME can increase cross sectional area (CSA) and symmetry of multifidus muscle, as well as activating the external oblique abdominal, and superficial descending pectoral muscles. The aim of this study was to objectively measure activity differences in m. longissimus dorsi (LD) and m. rectus abdominus (RA) whilst performing three levels of spinal flexion and lateral bending, as well as comparing thoracic and pelvic lift exercises in nine adult sport horses. Three repetitions of each exercise was performed for five seconds. Surface electromyography (sEMG) was used to record muscle electric activity, whilst sagittal lumbo-sacral flexion was measured with kinematics analysis. Overall, the results have shown that spinal flexion and lateral bending activate the m. rectus abdominis (RA) progressively as the exercise requires further reach, with a lateral bending effect evident on the ipsilateral side of RA. RA also had increased activation during thoracic lifts in comparison with pelvic lifts. M. longissimus dorsi (LD) has shown no significant differences in peak or average rectified EMG measures on the contralateral side during lateral bending. Pelvic lifts generated the greatest flexion of the lumbo-sacral (LS) joint. Results provide a guideline of the level of muscle effort required in relation to each exercise. Highlights M. rectus abdominis is activated more with further reach for cervical flexion and lateral bending. M. rectus abdominis is more active during thoracic lift than pelvic lift. Lumbo-sacral joint achieves greater flexion on pelvic lift exercises. M. longissimus dorsi responds very little to increased reach in DMEs.