A simple method for equine kinematic gait event detection

Abstract

Background
Previous studies have validated methods for determining kinematic gait events using threshold-based methods, however a simple method is yet to be identified that can be successfully applied to walk, trot and canter.

Objectives
To develop a simple kinematic method to identify the timing of hoof-on, peak vertical force and hoof-off, which can be applied to walk, trot and canter.

Study design
In-vivo method authentication study.

Methods
The horses (n = 3) were ridden in walk, trot and canter down a runway with four force plates arranged linearly. Three-dimensional forces were recorded at a sampling rate of 960 Hz and were synchronised with a ten-camera motion analysis system sampling at 120 Hz. Events identified from the vertical ground reaction force (GRFz) data were hoof-on (GRFz>50N), peak vertical force (GRFzpeak) and hoof-off (GRFz<50N). Kinematic identification of hoof-on and hoof-off events was based on sagittal planar angles of the fore and hindlimbs. Peak metacarpophalangeal/metatarsophalangeal (MCP/MTP) joint extension was used to assess the time of GRFzpeak. The accuracy (mean) and precision (s.d.) of the time difference between the kinetic and kinematic events were calculated for the fore and hindlimbs at each gait.

Results
Hoof-off was determined with better accuracy (range: -3.94 to 8.33 ms) and precision (5.43 to 11.39 ms) than hoof-on across all gaits. Peak MCP angle (5.83 to 19.65 ms) was a more precise representation of GRFzpeak than peak MTP angle (11.49 to 67.75 ms).

Main limitations
The sample size was small and, therefore, further validation is required. The proposed method was tested on one surface.

Conclusions
A simple kinematic method of detecting hoof-on, hoof-off and GRFzpeak is here proposed for walk, trot and canter. Further work should focus on validating the methodology in a larger number of horses and extending the method for use on surfaces with varying compliance.