Fig. 2

Effects of prolonged exposure to optical flow perturbations on foot placement kinematics. Group average (±standard error) of perturbation-induced effects on a step width (SW), b step length (SL), c step width variability (SWV), and d step length variability (SLV) for older participants. The area between the vertical dashed lines represents the period when visual perturbations were present. Previously published reference data from young participants walking for 8 min with optical flow perturbations is shown for comparison. The repeated measures ANOVA revealed significant (p < 0.001) main effects across the perturbation session (baseline, early, late, post) for all outcome measures. Single asterisks (*) indicate significantly different from baseline values in older adults (p < 0.05). Double asterisks (**) indicate significantly different between early and late time points for prolonged exposure in older adults. We also note differences approaching significance for post and baseline for step width (p = 0.056), between early and late for step width (p = 0.054), and between post and baseline for step length (p = 0.054) in older adult participants (^a)