Effect of walking velocity on forelimb kinematics and kinetics.

A database of biomechanical variables obtained from normal horses walking at a range of velocities is needed for comparison with the variables obtained from lame horses in which velocity cannot be predetermined. The objective was to investigate velocity-dependent changes in selected kinematic variables, ground reaction forces (GRF) and net joint energies in the forelimb and to develop statistical equations to calculate expected values of these variables for horses walking at different velocities. Five sound horses walked at a range of velocities (0.82 to 1.91 m/s) over a force plate. Kinematic data were recorded simultaneously for 51 trials. Kinematic, GRF and energetic variables were determined using standard methods. Correlation and simple regression analyses between velocity and measured variables were performed. An increase in walking velocity was correlated with an increase in stride length and decreases in stride and stance duration. Vertical, braking and propulsive impulses decreased as a consequence of the large reduction in stance duration, even though peak vertical, braking and propulsive GRFs increased. There was no significant increase in energy generation at any of the forelimb joints, indicating that muscle activity was not the source of the increase in GRFs. Changes in the longitudinal GRFs appeared to be influenced by velocity-dependent increases in head and neck oscillations. The equations obtained in this study can be used to calculate the expected normal variables from a range of walking velocities and to detect deviations from normal values in lame horses.