Do Ground and Raised Poles Affect Differential Rotational Movement of the Equine Thoracolumbosacral Spine During Straight Line Locomotion when Walking In-hand?

Background: Walking pole exercises are widely used for both training and rehabilitation of ridden horses, often as part of an exercise programme for horses with spinal dysfunction. There are limited data on the effect of pole work exercise on the kinematics of the thoracolumbosacral spine. 
Objectives: To quantify the effect of walking over ground poles (10 cm high) (GP) and raised poles (20 cm high) (RP) on kinematics of the thoracolumbosacral spine compared to walking over no poles (NP). 
Study design: Quantitative observational. 
Methods: Skin mounted inertial sensors were glued on to the midline of the back of 10 non-lame sports horses at thoracic vertebrae T5, T13, T18, lumbar vertebra L3, and tuber sacrale TS. In three random order repeats, horses were walked in-hand, in a straight-line over NP, and five consecutive GP and RP spaced at 90 cm. Differential rotational movement between adjacent sensors was analysed using a general linear mixed model with condition (NP/GP/RP) as fixed factor and horse as random factor (Bonferroni post hoc comparison, p ≥ 0.05). 
Results: Pitch (flexion-extension) increased at T13-T18 for RP (mean 9(S.D.)), (2.87°(0.2), p = 0.05) and at T18-L3 (2.61°(0.2), p = 0.03) compared to NP (2.49°(0.2)/2.2°(0.2)). Roll (axial-rotation) increased at T18-L3 for RP (10.6°(0.9), p < 0.001) compared to NP (9.0°(0.9)). Yaw (lateral-bending) decreased at T13-T18 for GP (6.9°(0.2), p = 0.05) compared to NP (7.4°(0.2)) and increased at T18-L3 (5.1°[(0.3), p = 0.04) compared to RP (4.2°(0.3)). At L3-TS yaw values increased for GP (5.2°(0.3), p < 0.001) and RP (4.1°(0.3), p = 0.005) compared to NP (3.8°(0.3)). 
Main limitations: Limb kinematics not quantified. 
Conclusions: An increase in pitch and roll differential rotations of the mid-thoracic and lumbosacral spine was found walking over RP compared to NP. Yaw rotations were increased at L3-TS when walking over GP and RP compared to NP. These changes in back movement should be considered when prescribing pole work exercise. 
Ethical animal research: Approved by the Royal Veterinary College ethics and welfare committee. 
Informed consent: Informed client consent was obtained for all animals. 
Competing interests: T. Pfau is owner of EquiGait Ltd providing gait analysis products and services. 
Sources of funding: Centaur Biomechanics.

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