Differences in gait complexity and variability between children with and without Developmental Coordination Disorder Karl S. Rosengren a, *, Frederik J.A. Deconinck b,c , Louis A. DiBerardino III. d , John D. Polk e , Jesse Spencer-Smith f , Dirk De Clercq c , Matthieu Lenoir c a Department of Psychology, Northwestern University, 2029 Sheridan Road, Evanston, IL, 60208,United States b Institute for Biophysical and Clinical Research into Human Movement, Manchester Metropolitan University, United Kingdom c Department of Movement and Sports Sciences, Ghent University, Belgium d Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, United States e Department of Anthropology, University of Illinois at Urbana-Champaign, United States f Department of Psychology, University of Illinois at Urbana-Champaign, United States In this study we use elliptical Fourier analysis (EFA) to examine differences in the complexity and variability of gait of typically developing (TD) children and children with Developmental Coordination Disorder (DCD). EFA can be used to describe closed-loop contours [1] such as phase portraits that have been used to characterize limb segment or joint motion during gait (e.g., [2–5]). This approach quantifies the complexity of a movement pattern by assessing the number of harmonics required to produce an accurate fit of the data. We utilized EFA to examine differences between the two groups of children in the complexity and variability of movement as captured by phase portraits of the shank and thigh movement for both legs. We also used this approach to examine differences in the symmetry of movement across the two limbs in both groups. Although phase portraits are useful for characterizing angular motion of a single body segment [2–5] and have been widely used to describe changes in angular segment motion during gait as a function of ontogeny or pathology (e.g., [4,5]) they have been used primarily for qualitative assessment [2–4]. While qualitative assessments may sufficiently characterize differences between individuals and groups, quantitative approaches may provide greater diagnostic power for detecting variations from normal gait patterns. Most quantitative approaches to gait analysis, have relied on relatively simple outcome measures, such as stride length, step width, single leg support time, range of motion, and symmetry indices (e.g., [6–15]) that are unable to assess the movement variability that takes place in individual body segments during the gait cycle. Similarly, previous methods for quantifying phase portraits (e.g., [2,16,17]) have not addressed questions of variability within gait cycles. Developmental Coordination Disorder is characterized by difficulties in gross and fine motor tasks in the absence of known pathologies or disorders. Co-occurrence with learning and/or behavioral problems (dyslexia, ADHD) is common, however, these problems do not explain the motor deficits experienced by children with DCD [18]. The movements of children with DCD are often described as clumsy and uncoordinated and lead to difficulties with performing many of the activities of daily living that TD children perform easily [19]. Many children with DCD have difficulty with balance control [20,21], especially in challenging situations [22,23]. The gait of children with DCD has been reported to differ qualitatively from that of TD children [24]. Children with DCD have been described as having poor head control, uncoordinated limb to Gait & Posture 29 (2009) 225–229 ARTICLE INFO Article history: Received 5 December 2007 Received in revised form 2 August 2008 Accepted 12 August 2008 Keywords: Developmental Coordination Disorder Gait Variability Complexity ABSTRACT We used elliptical Fourier analysis (EFA) to examine potential differences in the complexity and variability of gait of children with (N = 10) and without (N = 10) Developmental Coordination Disorder (DCD). Children with DCD generated movement patters with larger variability and complexity than typically developing (TD) children. In addition, children with DCD exhibited greater asymmetry in their movement patterns compared to TD children. Our results suggest that children with DCD have significantly greater difficulty producing consistent movement patterns both across their left and right legs and over repeated strides. EFA techniques show promise for distinguishing between different groups of individuals. ß 2008 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +1 847 491 5190; fax: +1 847 491 7859. E-mail address: k-rosengren@northwestern.edu (K.S. Rosengren). Contents lists available at ScienceDirect Gait & Posture journal homepage: www.elsevier.com/locate/gaitpost 0966-6362/$ – see front matter ß 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.gaitpost.2008.08.005