Stance phase kinematics and kinetics of horses trotting over poles

Abstract

Trotting over poles is frequently used therapeutically to restore swing phase ranges of joint motion. It is not known whether ground reaction forces (GRFs) increase as the swing phase limbs are lifted higher to clear the poles. Higher GRFs might be painful or jeopardise healing of musculoskeletal injuries. To measure stance phase kinematics and GRFs in the forelimbs and hindlimbs of horses trotting on level ground, over low poles and over high poles, and to test the hypothesis that trotting over poles is associated with increases in peak GRFs and impulses in the supporting hindlimb and forelimb compared with trotting over level ground. Repeated measures experimental study on horses with normal gait. Kinematic and GRF data were collected from 8 horses trotting on level ground under 3 conditions performed in random order: no poles, low (11 cm) poles and high (20 cm) poles spaced 1.05 ± 0.05 m apart. Spatiotemporal and angular kinematic variables and GRFs were measured during stance. Comparisons among conditions were made using repeated measures ANOVA (P<0.05) with Bonferroni correction for post hoc testing. The only GRF component that increased when trotting over poles was peak forelimb braking GRF. Forelimb vertical and braking impulses increased and the transverse impulse changed from medially to laterally directed. Extension of the metatarsophalangeal and metacarpophalangeal joints did not change. The fact that peak vertical forces and extension of the metatarsophalangeal and metacarpophalangeal joints did not increase when trotting over poles suggests that loading of the musculoskeletal tissues is comparable with that associated with trotting on level ground in horses with symmetrical movement at trot. The findings support the use of trot poles during rehabilitation from lameness in horses that move symmetrically. The generation of laterally directed forelimb transverse forces suggests that trotting over poles may recruit the forelimb adductor musculature.