Kinematic analysis of side-by-side stepping with intentional and unintentional synchronization

Interpersonal synchronization of stepping during side-by-side walking may assist in the rehabilitation of gait for mildly impaired individuals. However, little is known regarding the effects of step synchronization on lower limb movement kinematics. The purpose of this study was to compare normal treadmill walking to walking under conditions of intentional and unintentional synchronization of stepping. Twenty pairs of subjects walked on side-by-side treadmills independently, paired (side-by-side under conditions in which unintentional synchronization was likely to occur), and paired with forced synchronization (instructed to purposely synchronize stepping). Of these 20 pairs, six pairs (12 individuals) demonstrated unintentional synchronization for over 99% of the paired walking trial. An optical motion capture system was used to compare lower limb kinematics for each of the three walking conditions in these six pairs. The data indicated that forced synchronization of stepping resulted in steps that were significantly smaller and faster when compared to independent and unintentional synchronization conditions. In addition, stride time standard deviation was reduced for both the intentional and unintentional synchronization conditions, but these reductions were not significant. No differences were noted between the unintentional synchronization and independent walking conditions. These results suggest that unintentional synchronization might be preferable to intentional synchronization for gait rehabilitation in certain individuals. Additional work is necessary to understand the effects of side-by-side walking and its potential for use in a therapeutic setting.