October 8, 2015

High speed galloping in the cheetah (Acinonyx jubatus) and the racing greyhound (Canis familiaris)

Spatio-temporal and kinetic characteristics

The authors of the above article seek to explain why there is such a massive difference between the maximun speeds of cheetahs and greyhounds when they both have the same rotary gallop and have a similar body size and leg length. A rotary gallop is an asymmetrical gait where the feet fall in a circular sequence around the body (Hildebrand, 1959). By comparing the kinetics of both the greyhound and cheetah gallop, Hundson, Corr, and Wilson sought to figure out precisely how Cheetahs are able to outrun greyhounds by nearly a factor of two. The scientists used a force plate and high speed video monitoring to find that cheetahs "use a lower stride frequency/longer stride length than the greyhound at any given speed" (Hudson 1). 

Retired racing greyhounds from the UK were compared with Cheetahs from a zoo in the UK and from a Cheetah center in South Africa. The subjects were trained to chase a mechanical lure across a force plate with high speed cameras on either side, as seen in the diagram below.

  After comparing leg lengths of the two species, it was found that Cheetah has a longer average leg length and back length, which lets the cheetah achieve a longer stride length, which is directly correlated to a faster gallop. The backs of the greyhounds were less flexible than those of the cheetahs. In addition, cheetah claws allow the cheetah to have better grip on the ground, which allows them to apply larger propulsive forces while galloping. 

http://jeb.biologists.org/content/215/14/2425

Hudson, Penny, Sandra Corr, and Alan Wilson. "High Speed Galloping in the Cheetah (Acinonyx Jubatus) and the Racing Greyhound (Canis Familiaris): Spatio-temporal and Kinetic Characteristics." The Journal of Experimental Biology (2012): 2425-434. 

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