Jockey postures make things easier for horses and speed up races

In the world of horse-racing, the horses understandably get all the attention but much of the thrill of today's races depends on the jockeys. Their modern riding posture - the so-called Martini glass - has led to a dramatic improvement in race times, by making things much easier on their horses.

Modern horse-racing has been going on for over two centuries, but in its earliest days, jockeys would ride vertically. The modern, crouched style was only developed in the late 19^th century in the US. By 1897, it has been adopted in the UK and by 1910, it was a global phenomenon. The new posture clearly had benefits for the horses for in the few decades after its introduction, race times improved by 5-7%, more than they did in the subsequent century.

You might think that crouching down speeds up races simply by reducing drag on the horse, but not so. Jockeys may be bent over but they still sit fairly high on their mounts, much higher than, say, a track cyclist does on theirs. This high posture means that from the front, the total area of horse and rider doesn't change very much between the upright and modern riding styles. Less than 2% of the total work done by the horse's muscles is spent on overcoming this extra drag.

Instead, Thilo Pfau at London's Royal Veterinary College has found that the uncomfortable stance greatly reduces the burden on the horse by uncoupling its movements from those of its rider.

Pfau analysed the movements of three jockeys riding five racehorses, using a variety of sensors attached to the saddle and the jockeys' hats and belts. His readings showed that jockeys move out of phase with their mounts, so that as the horse is rising in its stride, its rider is falling. The upshot is that the jockeys stay relatively level during the race. The horses still have to support their weight, but they don't have to accelerate or decelerate them through each stride cycle. And that saves them a considerable amount of energy.

The same principle is at work in a bungee-powered backpack design that was announced three years ago. When we walk with a normal backpack on, the up-and-down movements of our hips causes the backpack to bob along too. Every step we take, the pack swings downwards with a large force that strains our shoulders and back. But Lawrence Rome minimised these forces by creating a backpack where the load is suspended from the frame by bungee cords. As the bungee-pack's bearer walks, the load bounces out of phase and stays relatively level, reducing the maximum force on the wearer by around 80%. 

The same applies to jockeys who, while small, still weight around an eighth of the horses' own body weight. If that extra load slams onto the animal on the downward part of every stride, the result will be a more tired and slower horse. The Martini-glass posture allows the jockey to act like the bungee-powered backpack, with his own legs acting as the cords.

Their steady posture belies the huge effort that jockeys have to make to reduce the burden on their mounts. Their legs must flex up and down to compensate for their horses' movements and actually, it seems that they slightly overcompensate.  As a result, their heartbeats skyrocket to around 180 beats per minute and they build up huge amounts of lactic acid. It's as physically demanding a sport as any other.

Reference: Science 10.1126/science.1174605

Image: from Science/AAAS

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