Usain Bolt may be looking to cement his Olympic track legacy at this year's London games, but in a competition for world's fastest sprinter, it's the cheetah that takes first place. Though pitting the Jamaican athlete against the speedy cat may not be a fair comparison—especially since in 2009 a cheetah named Sarah bested Bolt's record-breaking 9.69-second 100-meter dash by a good 3 seconds—scientists now know what makes the swift feline faster than similarly built speedsters, such as the racing greyhound. Using high-speed cameras, the team recorded cheetahs and greyhounds galloping across a track lined with force plates. By analyzing the two animals' sprinting patterns and contact forces, the researchers identified several biomechanical factors that help the cheetah outstrip its canine competition, they reveal today in The Journal of Experimental Biology. In addition to having longer stride lengths, cheetahs can increase the number of strides they make per second as they accelerate. While running at the leisurely pace of 9 m/s the cats used 2.4 strides per second, but when they sped up to 17.8 m/s they used 3.2 strides per second. Greyhounds on the other hand, sprinted with 3.5 strides per second regardless of how fast they were going. Surprisingly, in this study the dogs reached speeds of 19 m/s, which were faster than the captive cats' performance. The scientists think that wild cheetahs, which boast speeds of 29 m/s, can use 4 strides per second at their top speeds.
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