In 1897, an American jockey named Todd Sloan came to the United Kingdom and revolutionized the world of horse racing. Instead of dangling his legs down the sides of his horse, he squatted high in his stirrups. The British called the awkward-looking position the "monkey crouch," but the new seat quickly caught on: In the past century, jockeys using Sloan's technique have improved their race times by about 6%. Now researchers have figured out why the strategy is so effective.
Veterinarians in the Structure and Motion lab at the University of London's Royal Veterinary College have been working with the British Racing School in Newmarket to analyze the best and safest ways for jockeys to ride their horses. To determine just how energy-efficient Sloan's pose is, they attached identical sensors to a horse's saddle and to a jockey's belt. As the horse raced around the track, the sensors recorded the movements of both horse and jockey.
Even as horse and rider move forward, they also bob up and down with each stride. The researchers found that whereas a horse averaged a vertical change of 150 millimeters in each stride, the rider's vertical displacement was only about 60 millimeters. Jockeys "don't follow the movement of the horse but stay relatively stationary," says co-author Alan Wilson. By, in effect, floating above his mount, the jockey saves the energy the horse would otherwise expend to shove him back up after each bounce down into the saddle. Doing this is "very hard work," says Wilson, because the rider uses his legs in their short stirrups as springs or pistons. "It's a bit like skiing moguls," he says. Indeed, a jockey's heart rate while racing can reach 190 beats per minute.
No other change has brought such dramatic improvements in racing speed, biomechanics expert Thilo Pfau and colleagues report in tomorrow's Science. The average times--almost 109 seconds per mile in the 1890s--fell dramatically and settled at less than 103 seconds for most of the 20th century.
An analogous type of energy savings has been described by biologist Lawrence Rome of the University of Pennsylvania, who experimented with suspending a rucksack by bungee cords on a frame. The setup enabled the backpack to move less in relation to the movement of the person carrying it. "This is a similar case," says Rome. "Indeed, the horse is wearing a backpack!"