Intra-limb coordination while walking is affected by cognitive load and walking speed.

Knowledge about intra-limb coordination (ILC) during challenging walking conditions provides insight into the adaptability of central nervous system (CNS) for controlling human gait. We assessed the effects of cognitive load and speed on the pattern and variability of the ILC in young people during walking. Thirty healthy young people (19 female and 11 male) participated in this study. They were asked to perform 9 walking trials on a treadmill, including walking at three paces (preferred, slower and faster) either without a cognitive task (single-task walking) or while subtracting 1׳s or 3׳s from a random three-digit number (simple and complex dual-task walking, respectively). Deviation phase (DP) and mean absolute relative phase (MARP) values-indicators of variability and phase dynamic of ILC, respectively-were calculated using the data collected by a motion capture system. We used a two-way repeated measure analysis of variance for statistical analysis. The results showed that cognitive load had a significant main effect on DP of right shank-foot and thigh-shank, left shank-foot and pelvis-thigh (p<0.05), and MARP of both thigh-shank segments (p<0.01). In addition, the main effect of walking speed was significant on DP of all segments in each side and MARP of both thigh-shank and pelvis-thigh segments (p<0.001). The interaction of cognitive load and walking speed was only significant for MARP values of left shank-foot and right pelvis-thigh (p<0.05 and p<0.001, respectively). We suggest that cognitive load and speed could significantly affect the ILC and variability and phase dynamic during walking.