Head coordination in the sagittal plane in toddlers during walking: preliminary results

In adults, head rotations in the pitch plane are highly synchronized with vertical head translations during different locomotor tasks as walking, running, and hopping. The head is rotating up then down in the pitch plane as stepping movement drives the head down then up, respectively. The purpose of our study was to determine at which period of the motor control development this fine head coordination occurred. The organization of head movements was analyzed in four normal children observed longitudinally from the onset of walking up to 80 weeks of independent walking (IW). The degree of synchronization between vertical head translations and head rotations in the pitch plane was used to define an index of head coordination for 15 to 25 steps per child per session. Our results show that the coordination of head rotations in the pitch plane improves continually in toddlers but does not reach the optimal level during the first year of IW experience. We showed previously that head stabilization in space was achieved during the first weeks of IW. Both head stabilization in space and fine head coordination during walking are considered as directly involved in gaze stabilization, but in toddlers head stabilization in space is completed earlier than head coordination. Head stabilization appears to be a necessary motor control to acquire prior to the development of head movement coordination.