How does trotting over raised and ground poles on a circle and straight line alter equine spinal motion?

Background: Polework exercise is commonly used in equine training and rehabilitation programmes, but limited data is available describing the kinematics of the thoracolumbar spine when trotting over poles during circular locomotion.

Objectives: To quantify differential flexion-extension (FE), axial rotational (AR) and lateral bending (LB) range-of-motion (ROM) of the thoracolumbar spine when trotting in-hand over 10 cm ground poles (GP) and 26 cm raised poles (RP) compared to no poles (NP) during straight-line and circular locomotion.

Study design: Experimental.

Methods: Inertial measurement units were fitted at thoracic (T)7/12/lumbar (L)2 vertebrae, between tubera sacrale (SAC) and base of the tail (TAIL) of 17 riding horses. Horses were trotted in-hand over NP, five GP and five RP (distances set to 100% of horse's forelimb step length), with poles positioned on a straight-line and on a 15 m circle led from the left (three repeats, left/right reins). Differential FE/AR/LB were calculated and analysed using a two-way repeated-measures ANOVA with a significance of p ≤ 0.02 (alpha adjusted).

Results: Differential LB ROM at T12-L2 increased on the right circle compared to the straight (S: 9.4±0.7, CR: 8.0±0.4, p = 0.02) but no other differences between straight and circle were observed (p > 0.03). Raised poles increased differential LB at T7-T12 (RP:11.1±1.4, GP:8.4±0.7, NP:8.4±0.7, p = 0.02) and SAC-TAIL compared to GP/NP (RP:8.4±0.6, GP:6.4±0.5, NP: 6.9±0.5, p ≤ 0.001). Differential FE ROM of SAC-TAIL increased over RP compared to GP/NP (RP:6.6±0.4, GP:4.8±0.5, NP:5.9±0.4, p = 0.005,0.004) and decreased from GP to NP (p < 0.001). Differential AR ROM of SAC-TAIL decreased over GP compared to RP/NP (RP:13.0±0.8, GP:11.0±0.6, NP:12.5±0.6, p = 0.02,0.001).

Main limitations: Only in-hand trotting has been studied.

Conclusions: Trotting over poles increased spinal mobility on a straight line and 15 m circle compared to no poles, with similar kinematic effects of both. This suggests that both circling and straight lines could be appropriate when prescribing polework exercise for spinal mobility.