How does pole distance alter equine spinal and limb kinematics during in hand walking?

Background: Walking over poles has been observed to increase limb and thoracolumbosacral (TLS) range of motion (ROM) but there is limited information on the influence of pole distancing.

Objectives: To quantify limb and TLS kinematics when walking in hand over no poles (NP) and 10 cm ground poles set at 85%, 100% and 105% of step length.

Study design: Experimental.

Methods: Reflective skin markers (19 mm) were placed on the midline of six riding horses at thoracic (T)T6/T10/T13/T15/T17, lumbar (L)L1/L3/L5 vertebrae. Ten optical motion cameras (240 Hz) captured three passes of in-hand straight line walking over NP and five ground poles set at 85%, 100% and 105% of horse's forelimb step length. Fore and hindlimb protraction/retraction, hock and TLS flexion, extension and total ROM were calculated and analysed using repeated-measures ANOVA with an adjusted p-value (p ≤ 0.03).

Results: Fore and hindlimb protraction/retraction ROM was reduced at 85% compared to NP and 105% (NP: FL: 40.1±0.5, HL: 42.7±0.4, 85%: FL: 37.8±0.5, HL: 40.4±0.7, 100%: FL: 39.1±0.6, HL: 42.5±1.0,105%: FL: 40.6±0.5, HL: 43.5±0.5, p ≤ 0.02). Hock ROM was greater over poles compared to NP (NP: 35.4±0.6, 85%:58.8±2.1, 100%:64.0±3.6, 105%:62.9±1.8, p ≤ 0.001). Thoracic ROM at T10 (NP: 8.4±0.3, 85%:8.1±0.3, 100%:9.7±0.3, 105%:9.9±0.3, p ≤ 0.001), T13 (NP: 9.7±0.3, 85%:9.0±0.4, 100%:10.4±0.4, 105%:10.7±0.4, p ≤ 0.001) and T15 (NP: 9.5±0.3, 85%:8.7±0.3, 100%:9.8±0.4, 105%:10.3±0.3, p ≤ 0.001) increased, via extension, at 100%/105% compared to 85% (p < 0.001), but was only seen at 105% compared to 85% at T18 (NP: 8.5±0.3, 85%:7.9±0.4, 100%:8.5±0.3, 105%:8.9±0.3, p < 0.03). Poles at 85% reduced extension compared to NP at T10 only. Greater L2 extension was seen at 105% compared to NP/85% (NP: −3.5±0.7, 85%: −3.3±0.8, 105%: −2.53±0.6, p = 0.03), but ROM remained unchanged.

Main limitations: Only in-hand walk studied.

Conclusions: Walking over poles increases limb ROM, regardless of pole distance. However, TLS flexion-extension and limb protraction-retraction ROM are affected by pole spacing; if limiting spinal extension is a priority, reducing pole distance is recommended.