Meeting Abstract
Horses trot by synchronizing two pairs of legs and alternating support between them. We examined this synchronization by reducing each leg down to a phase oscillator and looking at the dynamics of the coupled oscillators representing a pair of legs that step in synchrony. Our recent work on near simultaneous transitions in hybrid dynamical systems suggested that touchdown may act to synchronize legs without neural feedback, provided legs touch-down independently but lift-off in a coordinated fashion. Using an existing dataset of 5293 strides, from 54 trials with 6 horses (Irish thoroughbred) we tested this hypothesis. We reduced each leg to a phase oscillator, mapped the touchdown and liftoff transition in phase coordinates, and examined the phase coupling for expansion and contraction in various parts of the cycle. Our results showed that while the hypothesized hybrid transition structure was present, touchdowns were associated with a decrease instead of an increase in synchronization. Legs were brought back into synchrony in a continuous region in the second half of stance. We conclude that while the hybrid synchronization effect might be present and active, the only clearly detectable form of synchronization acts continuously during the second half of stance.
