AbstractThe purpose of this study was to compare the effects of manipulating visual and somatosensory information during a multiple obstacle clearance task between children and adults. It was hypothesized that compared to adults, children would have difficulty with motor planning and online control during a multiple obstacle crossing task when sensory information was manipulated. Children (N=16,x ?=9+-1.07years) and adults (N=16,x ?= 22+-0.96years) walked along a 7m pathway towards a goal while avoiding stepping on one, or two obstacles. Visual information regarding the number of obstacles was either presented at the start of locomotion, or two steps prior to the first obstacle. Each participant completed thirty-six trials, 18 on flat ground and 18 on foam terrain. Full body kinematic data was collected using the NDI Optotrak motion analysis system (60Hz). Lead and Trail limb foot position variability were determined relative to the first obstacle. For Lead foot variability, there was an interaction between obstacle appearance, type of terrain, and age group, such that children were more variable on foam when obstacle appearance was delayed (F(1,29)=6.16,p=0.02). For Trail foot variability, there was an interaction between the amount of visual information provided and age group (F(1,29)=10.55,p=.003). Children were more variable when obstacle appearance was delayed compared to adults. The present study found that children have difficulty with online control of locomotion and demonstrate immature motor planning strategies. Children use visual information in a feedforward manner, rather than an online control, resulting in high variability in obstacle clearance behaviours when unexpected obstacles need to be avoided.