Speed control in quadrupedal locomotion: principles of limb coordination in the dog.

Long distance, overground locomotion in the dog was observed and analyzed using the two dimensional gait diagram method. Though the velocity of locomotion chosen by the animals over a 1,000 m course varied, a preferred speed generally emerged and was used during most of the experiment. This animal-specific preferred overground velocity was strongly correlated with the animal's limb lengths, and corresponded to the minimum observed swinging velocity of the limbs. Changes in the pattern of limb coordination during three-limb locomotion were also investigated. Depending upon which limb was restrained, dogs used trot-like or gallop-like gaits which exhibited the same temporal and spatial phase differences as were observed during normal locomotion. However, stride length and swing-stance durations were increased relative to those observed in four legged locomotion. Animals with an additional 2 kg weight trotted slowly, but no significant changes in limb movement parameters were found. Locomotion studies performed in darkness resulted in an immediate switch from asymmetrical (galloping) to symmetrical gaits (walking and trotting). These gaits allow for precise foot placement.