Age-related differences in locomotor targeting performance under structural interference

Methods: forty older (n = 20, mean age = 77.9) and younger (n = 20, mean age = 25.2) participants walked 11.6 m while stepping on a target positioned at the 9.5 m point. Participants completed seven trials under each of three conditions, including the control (C) (no structural interference), low structural interference (L) and high structural interference (H). The structural interference conditions required participants to engage in LT while simultaneously verbally identifying letters that were visually presented on one of two monitors. One monitor was located near the target (low interference), while the other monitor was elevated to require participants to direct their gaze further away from the target to identify a letter (high interference). Outcome measures included LT error, SL, SL variability and the distribution of SL adjustment. Results: structural interference had a detrimental effect on the LT accuracy of the older group (2.75 cm mean increase in absolute error) but not on the younger group (1.05 cm mean increase in absolute error), even though the interference caused the older group alone to adopt a more conservative gait pattern involving shorter SLs. The older participants exhibited shorter mean SL with each increase in structural interference (conditions C vs. L, P = 0.004; conditions L vs. H, P = 0.050), whereas the younger participants' mean SL did not differ across conditions. The manner in which older and younger participants distributed SL adjustment across the steps in advance of the target did not differ. Conclusions: the results confirmed that LT demands more attention from older adults than it does from younger adults, and revealed that a consequence of this age difference is a decline in LT accuracy among older adults. The study implicates age-related impaired visual attention switching as a potential source of impaired walking performance among older adults.