Control of locomotion velocity in tetrapods.

Speed control mechanisms were investigated during overground locomotion in the dog. Swing and stance durations as well as stride length were measured for the four limbs simultaneously. Other locomotion parameters such as the mean velocity of the run, phase shifts, step length and the mean velocity of limb transport during the swing phase were calculated on the basis of the measured parameters. It was shown that the increase in stride length was almost linear in relation to the increase in locomotion velocity. There were similar changes in the stepping frequency although changes of this parameter were not strictly linear and depended on changes of step length. During moderate trotting the amplitude of limb movements was almost constant and the velocity of limb transport during the swing phase was minimal. Moreover in the symmetrical gaits spatial phase shifts between unilateral limbs were equal to zero, which means that hind and fore limbs were placed in the same point during successive steps.