Examining anticipatory turn signaling in typically developing 4- and 5-year-old children for applications in active orthotic devices

To develop active pediatric orthotics, it is important to accurately predict alterations to a straight path, such as turns. In this study we examine anticipatory signals prior to a pre-defined turn in seven healthy children. Subjects walked along a predefined 4.25 m straight path and then made either a 40-degree turn left or right, or continued straight based on a pre-set color panel at the endpoint. The forward center of mass (COM) velocity for the stride prior to the turn region was 1.16 ± 0.22 m/s (no significant difference was seen with respect to turn direction, p > 0.05). In the stride prior to landing in the turn region, subjects showed a significant difference in the mediolateral COM velocity with respect to the turn direction (p = 0.003 for 30% and p < 0.0005 for 40-100% of the gait cycle). No significant differences were observed in the sagittal plane kinematics of the hip, knee, or ankle during the preparatory stride with respect to turn direction (p > 0.05) when compared at 10% gait increments. However, significant differences were observed in pelvic rotation for 10-30% (p < 0.05) and 70-100% (p < 0.0005) of the gait cycle. The subjects were inconsistent in strategy used to perform a turn. In trials to the left and right, 66% and 56% of the trials were step turns, respectively. The varying turn strategy may be a function of limited instructions provided to the child, or ongoing development in the children's COM control. Yet even with the varying strategies, there exist anticipatory signals that can be used to design real-time controllers for assistive devices with readily available sensor systems.

► Subjects began to shift their body in the direction of the turn in the preparatory stride. ► No significant differences in sagittal plane kinematics in the preparatory stride. ► Significant differences in the pelvic rotation in the preparatory stride. ► Inconsistent strategies to perform a turn. ► Anticipatory signals exist to design real-time controllers for assistive devices.