A role for the lower visual field information in stair climbing

Background: Locomotion on stairs is challenging for balance control and relates to a significant number of injurious falls. The visual system provides relevant information to guide stair locomotion and there is evidence that peripheral vision is potentially important. Research question: This study investigated the role of the lower visual field information for the control of stair walking. It was hypothesized that restriction in the lower visual field (LVF) would significantly impact gaze and locomotor behaviour specifically during descent and during transition phases emphasizing the importance of the LVF information during online control. Methods: Healthy young adults (n = 12) ascended and descended a 7-step staircase while wearing customized goggles that restricted the LVF. Three visual conditions were tested: full field of view (FULL); 30 degrees (MILD), and 15 degrees (SEVERE) of lower field of view available. Stride time, head pitch angle and handrail use were assessed during approach, transition steps (two steps at the top and bottom of the stairs) and middle step phases. Results: Transient downward head pitch angle increased with LVF restriction, while walk speed decreased and handrail use increased. Occlusion impaired stair descent more strongly than ascent reflected by a larger downward head pitch angles and slower walk times. LVF restriction had a greater influence on stride time and head angle during the approach and first transition compared to other stair regions. Significance: Information from the lower visual field is important to guide stair walking and particularly when negotiating the first few steps of a staircase. Restriction in the lower visual field during stair walking results in more cautious locomotor behaviour such as walking slower and using the handrails. In daily activities, tasks or conditions that restrict or alter the lower visual field information may elevate the risk for missteps and falls.