HOOVES EUROPEAN TRAINER ISSUE 48_Jerkins feature.qxd 17/12/2014 01:57 Page 2
HOOVES AND GROUND SURFACE
HOOVES AND GROUND SURFACE The impact of intentional shoeing interventions
The interaction of a horse’s foot and the ground surface is complex. Stance – that part of the stride when the foot is in contact with the ground – can be divided into three phases, which determine the loading environment of the limb: impact, mid stance and push off. Loading of the limb determines how it functions and also influences where injury may occur. Research funded by the Horserace Betting Levy Board at the Royal Veterinary College has focussed on the foot and is allowing a greater understanding of the effect of changes in surface or shoeing on stance, on remodelling of the tissues and ultimately on the risk of injury. WORDS: DR THOMAS WiTTe, ROyAl VeTeRinARy COllege pHOTOS: FRAnK SORge, ROyAl VeTeRinARy COllege
Fine-tuned for high speed The horse’s limb has evolved for efficient locomotion and high-speed performance, and lacks a lot of the adaptability for variations in underfoot conditions of other legged animals. Racehorses encounter a wide range of surfaces and are subject to a variety of interventions that alter the interaction of hoof and surface. Improved understanding of the links between surface, performance and injury can have a major impact through the design of surfaces and modification of shoeing strategies. The equine limb is designed for efficient and high-speed locomotion. Adaptations that achieve this include reduced bone mass and concentration of muscle in the upper limb to allow rapid limb advancement. The hindlimbs propel the horse forwards, or upwards during jumping, while the forelimbs provide vertical support of body weight. There is a small amount of muscle in the lower limb, but this does not produce or control movement; instead it damps vibrations. Tendons are long and elastic, and this reduces energy use while the bicep has a large internal tendon acting like a catapult for rapid limb advancement.
Vulnerable to surface changes Optimisation of the horse’s limb for speed and energy efficiency comes at some cost to adaptability. Unlike human athletes who can alter leg stiffness from one stride to the next in response to changes in surface properties,
horses have relatively constant leg stiffness across surface, speed, gradient and even gait. In fact, even changes in gait are limited and the duration of the swing and aerial phases of the gallop are relatively constant across changes in speed. The locomotor system of the horse is therefore very vulnerable to changes in the foot-surface interaction. Small changes in
A horse equipped with hoof-mounted accelerometers (red arrows), reflective markers for filming with high-speed video (blue arrows) and a body-mounted inertial measurement unit with inbuilt GPS (green arrow). This minimally invasive setup is being used to measure hoof contact, the angle of lean, speed and precise horse location during regular gallop training, and can be deployed in larger numbers of horses repeatedly than has been possible with more invasive measurement techniques.
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