The team found that when a dog's hind leg is missing, the front legs continue to function as they normally would, with little or no modification needed. But when a dog has lost a front leg, the remaining limbs must undergo extreme adaptation to coordinate with each other, in a strategy known as "gait compensation." The researchers believe this is because fore-limbs are loaded more and have a much greater influence on the distribution of body weight in a four-legged animal. "Natural terrestrial locomotion is designed for an even number of limbs," said the study's lead researcher Martin Gross of the University of Jena in Germany. "After limb loss, a reorganization of the locomotive system is required."