Fig. 9. Head pitch (solid line) and head vertical (broken line) displacements during all walk (A), trot (B), and canter (C) cycles for all three horses. Data are smoothed (6 Hz cut-off frequency for walks, 8 Hz for trots and canters) and the mean values have been subtracted for each cycle to yield change in pitch cycle and vertical position. The angular and linear displacements of the head were consistently in-phase for walks but had shifting phase relationships for trots and canters.