Characteristics of single and double obstacle avoidance strategies: a comparison between adults and children

Abstract

Activities of daily living often require us to negotiate several obstacles in the travel path. To date, there is little work investigating how adults accomplish such tasks, and there is even less known about multiple obstacle avoidance strategies used by children. The current work will expand our knowledge about the role of vision in adults and children when avoiding two obstacles placed in their travel path under altered ambient lighting. Healthy 7-year old children (n=10; aged 7.51+/-0.2 years) and adults (n=10; aged 22.76+/-1.7 years) were instrumented with infrared markers (Optotrak, NDI) placed on anatomical landmarks and asked to walk along a ten meter path under three conditions: unobstructed, single obstacle, or double obstacle. These trials were performed under two lighting conditions: Full (simulating standard office lighting) and Low (simulating a dark hallway lit by nightlights). Data analyses included lead and trail clearance values, step length, step width and step velocity, take-off distance and Horizontal toe Displacement at Apex (HDA) which was defined as the distance between the horizontal position of the toe to the leading edge of the obstacle when the toe reaches its peak height. Adults were able to maintain consistent behaviour regardless of the number of obstacles in the travel path. Children, however, adjusted their foot placement for the second obstacle. This indicates that having multiple obstacles in the travel path is a more challenging task for 7-year old, and suggests that children at this age may not have fully developed anticipatory locomotor strategies. Children had larger clearance values than adults for the lead foot crossing the obstacle under all obstacle and lighting conditions, and consistently used larger HDA values than adults. Together, these findings suggest that children adopt more cautious strategies than adults in complex environments. Additionally, children decreased walking velocity, increased step width and decreased their step length in a Low light environment. These changes are all indicators of a more careful avoidance strategy, which implies that children at this age rely heavily on visual information to guide foot placements in a complex environment.

The effect of treadmill walking on the stride interval dynamics of children

“…Contrarily, adults have demonstrated significantly elevated dynamics during STW (Chang et al, 2009b). Children and adults are thought to perceive sensory information differently, or use the available information to a different extent (Berard and Vallis, 2006). To this end, postural stability studies suggest that, unlike adults, children are unable to precisely couple body sway with somatosensory information provided by fingertip touch (Barela et al, 2003).…”

“…Irrespective of the neural circuitry responsible for stride dynamics, the age-sensitivity of these complex patterns would certainly seem to suggest that either: (i) neural feedback being sent to control centers change with age (Berard and Vallis, 2006), or (ii) control centers themselves develop with age and thus differ in their ability to receive, integrate, or process the motor output signals (Martin, 2005;Watanabe et al, 2007). It is well established that that human nerve and muscle cells are postmitotic, and therefore present to their greatest extent after early development (Vandervoort, 2002).…”

Locomotor Adjustments Made by Toddlers While Stepping Over Obstacles

“…With increase of age, older children are more capable to exert prospective postural control to accomplish specific locomotor tasks. In terms of locomotor adjustments, performance of older children is closer to that of young adults Krell & Patla, 1997;MacFadyen, 2001;Vallis & MacFadyen, 2005;Berard & Vallis, 2006).…”

“…In particular, when children of this age group attempted in circumvent multiple obstacles, inconsistent locomotor anticipatory adjustments were exhibited and other compensatory actions were employed to achieve safe margins over the obstacles (Krell & Patla, 1997;Vallis & McFadyen, 2005, Berard & Vallis, 2006.…”

“…Without the appropriate take off foot position prior to the obstacle, higher toe clearances and greater crossing step lengths were used to ensure safety during obstacle crossing (Krell & Patla, 1997;Berard & Vallis, 2006). In addition, suitable anticipatory adjustments for preparing the action of going over an obstacle are made according to the reference system for body orientation.…”