Statistical analysis
Shapiro-Wilk test verified that all variables were normally distributed. Background variables (i.e., height, weight, serial-7 sitting, hand grip strength, 30CST, BPAQ, and treadmill walking speed) were compared between groups using ANOVA followed by post hoc analyses. A 3 X 2 X 2 repeated measure ANOVA and planned comparisons were used to determine the effect age group (young, middle age, Old) X lighting condition (usual lighting, near-darkness) X dual task (with/without dual task) on each gait outcome. An additional ANOVA examined the effect of age group on serial-7 task performance during walking (serial-7 walking). Partial η2 effect sizes were calculated for each ANOVA model, with η2 = 0.01 indicating a small effect, η2 = 0.06 indicating a medium effect, and η2 = 0.14 indicating a large effect [