Algorithm proves accurate in detecting break-over phase in a horse’s stride


An algorithm developed by researchers for use with inertial measurement units has proved accurate in identifying the crucial break-over phase in a horse’s stride.

The algorithm could prove useful in pinpointing longer break-over phases, which can indicate musculoskeletal problems.

The break-over phase starts after the loading phase when the horse lifts its heel, causing a rotational movement around the toe, and ends with hoof lifting off.

During this rotation, the body weight moves towards the toe, reducing the contact area with the ground and increasing the force on the toe and navicular bone.

This increase in force results in high tensile forces on the muscles, ligaments and tendons. It is influenced by gait and speed.

A prolonged break-over phase might increase the risk for development of navicular disease and tendon injury. Longer break-over phases can also be a result of a mechanical restriction or pain and indicate lameness or an orthopedic disorder.

Marij Tijssen and her colleagues at Utrecht University in The Netherlands set out to test the ability of an angular velocity algorithm and acceleration algorithm to detect the break-over phase and, if successful, to assess their accuracy.

The break-over phase can be measured from data collected by optical motion capture systems, inertial measurement units or force plates.

Their hope was that the algorithms would automatically detect the onset of the break-over phase at the walk and trot from the acceleration and angular velocity signals measured by inertial measurement units mounted on the hoof.

Generic illustration of the movement of the hoof (A), modified from a study by T.H. Witte and others; the signals of the acceleration (B), angular velocity (C), vertical force and first derivative of the vertical force (D), and vertical displacement of the heel and toe markers of the optical motion capture system. The start of the break-over is depicted with the vertical dashed lines and the dots show the detected break-over from the different signals. The swing phase is underlined with a dark beam.

Seven Warmblood horses were used in the study, which was reported in the open-access journal, PLOS ONE. Each horse was equipped with an inertial measurement unit on the side wall of their right front and right rear hooves.

Horses were walked and trotted over a force plate for internal validation while, simultaneously, the three-dimensional position of three reflective markers also attached to the hoof area was measured by six infrared cameras as part of an optical motion capture system.

A total of 147 trials were analyzed.

The acceleration algorithm was found to be the best performer, with an accuracy between -9 and 23 milliseconds and a precision around 24 milliseconds (against the motion capture system); and an accuracy of between -37 and 20 milliseconds and a precision around 29 millseconds (against the force plate), depending on gait and hoof.

“This algorithm,” they said, “seems promising for quantification of the break-over phase onset although the applicability for clinical purposes, such as lameness detection and evaluation of trimming and shoeing techniques, should be investigated more in-depth.”

The authors said a more extensive validation process should be performed with more data and additional horses.

Tijssen M, Hernlund E, Rhodin M, Bosch S, Voskamp JP, Nielen M, et al. (2020) Automatic detection of break-over phase onset in horses using hoof-mounted inertial measurement unit sensors. PLoS ONE 15(5): e0233649.

The study, published under a Creative Commons License, can be read here

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