Greyhounds are typically a healthy and long-lived breed, and hereditary illness is rare. Some Greyhounds have been known to develop esophageal achalasia, gastric dilatation volvulus (also known as bloat), and osteosarcoma. 'Double suspension rotary gallop' describes the fastest running gait of the Greyhound in which all four feet are free from the ground in two phases, contracted and extended, during each full stride. The key to the speed of a Greyhound can be found in its light but muscular build, large heart, highest percentage of fast twitch muscle of any breed, double suspension gallop, and extreme flexibility of its spine. 'Double suspension rotary gallop' describes the fastest running gait of the Greyhound in which all four feet are free from the ground in two phases, contracted and extended, during each full stride. 'Thoroughbreds and Greyhounds: Biochemical Adaptations in Creatures of Nature and of Man' Circulation, Respiration, and Metabolism Berlin: Springer Verlag 1985.