Preliminary evidence of a relationship between quantitative measures of postural stability and clinical movement tests in Developmental Coordination Disorder

Developmental Coordination Disorder is typically assessed using qualitative clinical measures. However, little is known about the relationship between these measures and quantitative measures of postural stability, such as variability in Center of Pressure (CoP), commonly referred to as sway. The present study administered two clinical measures commonly used to assess DCD (MABC and DCD-Q), and measured postural stability during static and dynamic balance tasks. The static balance task (Quiet Standing) consisted of 2 conditions lasting 30 seconds each, during which the participant stood still in a natural stance with his or her eyes open, then closed. The dynamic balance task (Visual Tracking), a novel contribution to the literature on DCD, involved the participant leaning to match his or her CoP to match a dynamic target displayed in a virtual environment on a 180° wrap-around screen. The target oscillated at 8 frequencies ranging from 0.1-0.8 Hz, and changed speed randomly without warning. Participants were 8 children with DCD aged 8-10 from a variety of ethnic backgrounds. Correlation analyses showed significant negative relationships between DCD-Q score and medial-lateral sway during both the eyes open (r = -0.79, p = .02) and eyes closed (r = -0.81, p = .02) conditions of Quiet Standing. MABC total score was negatively related to the participant’s average deviation from the target position in Visual Tracking (r = -0.76, p = .03), such that participants with higher scores on the MABC were more accurate at the dynamic movement task. We also correlated Quiet Standing and Visual Tracking performance, examining each frequency separately (averaged across 2 runs per frequency). CoP velocity was related to anterior-posterior sway in the eyes closed condition of Quiet Standing, while CoP position was related to medial-lateral sway in the eyes open condition. This pattern of results suggests that quantitative data may offer a more detailed means of assessing postural stability in children with DCD than common clinical tests. However, a larger sample is needed to detect and interpret meaningful relationships between variables, specifically between frequencies in the Visual Tracking task.