A biomechanical study of gait initiation in Down syndrome

Background: Gait Initiation (GI) is a functional task that challenges the balance control requiring weight shift and a transition from standing to walking. Individuals with Down Syndrome (DS) walk with low velocity, prolonged stance and shorter steps beside an increased support base. However, no studies performed GI analysis on this population. The aim of this study is to quantitatively characterize the GI task in subjects with DS compared with a typically developed control group. Methods: Seventeen individuals with DS (17 to 40 years) and 19 healthy subjects (17 to 40 years) were enrolled in the study. Data were acquired using an optoelectronic motion capture system and force plates in order to measure the displacement and velocity of Center of Mass (CoM) and the trajectory of Center Of Pressure (CoP). All participants were asked to stand barefoot on the first force platform and received a verbal cue to begin walking for 6 gait initiation trials (three starting with each foot). The CoP duration, velocity, length and excursion were calculated during the anticipatory postural adjustments phases (APAs) and the locomotor (LOC) phase. For the analysis of the CoM, its displacements in antero-posterior (AP) and medio-lateral (ML) during the APAs and LOC phases. Statistical analysis was conducted to compare the two groups. Results: Regarding CoP measures, when compared to control group, individuals with DS presented higher durations, lower velocities, longer lengths during the second APA and total phases, and shorter lengths during the first APA and LOC phases. The group with DS also presented longer CoP excursion during the second APA, whereas a shorter excursion was present during the first APA and LOC phases. The AP excursion in CoM is reduced in the participants with DS. Conclusions: Our results could be useful in the rehabilitation of individuals with DS as they suggest to reinforce exercise programs to improve balance in AP and ML directions, which is demonstrated to be impaired in these subjects.