Effects of Jumping Phase, Leading Limb, and Arena Surface Type on Forelimb Hoof Movement

Abstract

During the stance phase of equine locomotion, ground reaction forces are exerted on the hoof, leading first to rapid deceleration ("braking") and later to acceleration ("propulsion") as the hoof leaves the ground. Excessive hoof deceleration has been identified as a risk factor for musculoskeletal injury and may be influenced by arena surface properties. Therefore, our objective was to evaluate the effect of arena surface type (dirt, synthetic) on hoof translation of the leading and trailing forelimbs during jump takeoff and landing. Solar hoof angle, displacement, velocity, and deceleration were captured using kinematic markers and high-speed video for four horses jumping over a 1.1 m oxer at 12 different arenas (5 dirt, 7 synthetic). Surface vertical impact and horizontal shear properties were measured simultaneously. The effects of surface type (dirt, synthetic), jump phase (takeoff, landing), and limb (leading, trailing) on hoof movement were assessed using ANOVA (p < 0.05), while the relationships of hoof movement with surface mechanical properties were examined with correlation. Slide time (p = 0.032), horizontal velocity of the hoof (p < 0.001), and deceleration (p < 0.001) were greater in the leading limb, suggesting a higher risk of injury to the leading limb when braking. However, surface type and jump phase did not significantly affect deceleration during braking.

Keywords: arena surface; equine; hoof slide; leading limb; motion capture; show jumping.

Figure 1

Scaled diagram of jumping grid (top) and photograph of jumping grid (bottom). Two high-speed cameras were used to record takeoff and landing of the final 1.1 m oxer.

Figure 2

Photograph of hoof extension bar including: (a) A rectangular hoof block which remained rigidly attached to the hoof wall throughout the study period; (b) a hoof wand with kinematic markers to track hoof rotation and translation.

Figure 3

Definition of solar hoof angle (SHA): (a) Negative angles indicate that the dorsal wall of the hoof is rotated clockwise with respect to the arena surface (“toe up” orientation); (b) an angle of 0⁰ indicates that the solar surface of the hoof is parallel to the surface; (c) positive angles indicate that the dorsal wall of the hoof is rotated counterclockwise with respect to the arena surface (“toe down” orientation).

Figure 4

Subphases of stance: (a) Slide was defined as the region between the start of the stance phase and the end of horizontal hoof movement; (b) grab was defined as the region near the end of stance where the toe sank deeper into the surface. Support captured the period of the stance phase between slide and grab, where horizontal and vertical hoof displacement were minimal. Graphs depict hoof movement for a single horse at takeoff. Sample graphs depicting hoof movement at landing are presented in the Supplementary Material (Figure S1).

Figure 5

Average SHA normalized to percent stance at takeoff (gray) and landing (black). Bars indicate a 95% confidence interval for SHA at each percent stance.

Figure 6

Average SHA normalized to percent stance for dirt (brown) and synthetic (gray) surfaces at (a) takeoff; (b) landing. Bars indicate a 95% confidence interval for joint angle at each percent stance.