Biomechanics studies of galloping have a long and august history. In 1878 Eadweard Muybridge's photographs of a galloping horse, taken with 24 cameras at Stanford University, proved what the human eye could not see: that the galloping animal becomes airborne for a brief instant during each stride. Since then, horse biomechanists have used increasingly sophisticated technologies to resolve the complexities of galloping, including high speed film, force plates and treadmills. More recently Kevin Parsons, a vet from The Royal Veterinary College in Hertfordshire, UK, working with Thilo Pfau and Alan Wilson, have developed a system of accelerometers, worn by horses and coupled with GPS, to accurately measure horses' stride patterns to find out how the animals gallop up slopes().
But scientists aren't the only people intrigued by galloping horses. Parsons explains that the horse racing industry is keen to understand how horses negotiate different terrains and surfaces; `they want to know how exercising on inclines affects the forces on horses' legs because higher forces can cause injuries', he says. Working with a world famous trainer, the team travelled to Somerset to test out their accelerometer set-up on elite galloping thoroughbreds to find out how the animals modify their gait while ascending a slope.
According to Parsons he was up before dawn each day to collect data as the horses and their jockeys went out for training runs. Parsons explains that his data collection had to fit in with the horses' training regime and adds that`the jockeys aren't negotiable; we needed the horses to gallop on the track,and the horses won't gallop unless the jockey's there'. Taking advantage of this, Parsons attached a GPS system to the jockey's hat to track the horse's location, as well as gluing accelerometers to all four of the animal's hooves,before the horse joined a chain of thoroughbreds heading out to the track. Then it was a case of keeping his fingers crossed; `If one accelerometer failed, the data set was useless' he remembers.
Fortunately after a week at the stables, Parsons returned to The Royal Veterinary College with almost 5000 galloping strides to analyse. Correlating the jockey's GPS location with the time each hoof spent in contact with the ground, Parsons was able to distinguish between strides on the flat and strides as the horse climbed. Parsons admits that manually transcribing each hoof beat was tedious, but eventually he was able to calculate the forces on each leg and found that the back legs generated more force to power the horse up the hill than the front legs. Parsons suspects that this information could help trainers working with injured animals to reduce the forces on injured forelimbs during rehabilitation.
Knowing that trotting horses reduce their stride frequency as they ascend an incline, Parsons calculated the gallopers' stride frequency and was surprised to see that it had increased; the ascending horses were swinging their legs faster, just like a human runner. Parsons suspects that there could be two explanations for the increase. Either the leg contacts the rising ground more quickly at the end of each swing, or the elastic tendons in the horse's leg stores more energy to catapult the leg forward more quickly.
