Head stability and coordination variability during locomotion under different visual task constraints as a function of repetitive head impact exposure.

Repetitive head impact exposure in contact sports such as ice hockey has been shown to modify motor performance which could impact the control of head movement and result in perceptual deficits. However, how such exposure influences the coordination dynamics underlying head stability control, and thus visual perception, is not well understood. The purpose of this study was to assess whether contact sport participation affects coordination variability and stability during locomotion as a function of different levels of visual task constraints. Ice hockey (contact) and baseball (noncontact) athletes completed treadmill walking tasks with varying levels of visual task constraints. Head and trunk local dynamic stability and whole-body coordination variability were assessed at preferred and fast speeds with and without a dynamic visual acuity task. While no group differences in dynamic visual acuity were present, contact athletes displayed reduced vertical head local dynamic stability compared to non-contact athletes while walking at a fast speed without the visual task. Contact athletes also displayed lower whole-body coordination variability compared to noncontact athletes. These findings suggest that contact sport participation may lead to changes in head stability control and lower levels of coordination variability, suggestive of reductions in movement flexibility and adaptability.