Young and older adults use body-scaled information during a non-confined aperture crossing task.

Young and older adults demonstrate differences in action when passing through confined spaces (Warren and Whang in J Exp Psychol Hum Percept Perform 13:371-383, 1987; Hackney and Cinelli in Gait Posture 33:733-736, 2011). However, it is unknown whether or not these differences in actions exist during non-confined multiple obstacle avoidance tasks. The current study aimed to determine: (1) the differences in actions between young and older adults when given a choice in path selection and (2) establish the variables that may account for these differences in action. Older adults (N = 12) and young adults (N = 12) walked along a 10-m path towards a goal and avoided two vertical poles placed halfway down the path on either side of the midline (ranging between 0.6 and 1.8× shoulder width). Results revealed that in non-confined space, both age groups use body-scaled information to determine the passability of apertures and maintain similar Critical Points to those reported in confined aperture crossing (1.4 for young adults and 1.6 for older adults). Variability of the medial-lateral centre of mass movement (i.e. how much the trunk moved side to side) between the groups most likely accounted for the larger aperture sizes (i.e. Critical Points) required by the older adults to pass through the apertures. Therefore, it appears that body-scaled information may include an individual's knowledge of both actual body size and body sway magnitude.