The purpose of this study was to investigate differences in the patterns of supine spontaneous leg movements produced before sitting onset between infants with typical development (TD) and infants at risk for developmental delay (AR). In this cross-sectional, observational study, 35 infants were included; 18 infants with TD (130.4 ± 38.0 days) and 17 infants AR (124.1 ± 65.7 days). Infants were placed in the supine position and video taped for four to five minutes while in an alert, content state. After the recording, videos were coded frame by frame to identify the type of each leg movement produced: single flexion, single extension, alternate flexion, alternate extension, parallel flexion, parallel extension, leg wave, leg circle, leg thump, foot rub, foot flexion, or foot rotation. Unilateral movements (single flexion and single extension) were the most common leg movements in the TD group. Infants in the AR group produced a significantly lower proportion of unilateral and foot rub movements than infants with TD. These results provide a foundation of the types of leg movement pattern differences to build on in future research. Knowledge about differences in spontaneous movement patterns between infants in the AR group and infants with TD has relevance both for early identification of neuromotor impairment and clinical practice.
Weiyang Deng, Douglas L. Vanderbilt and Beth A. Smith
Beth A. Smith, Nick Stergiou and Beverly D. Ulrich
In previous studies we found that preadolescents with Down syndrome (DS) produce higher amounts of variability (Smith et al., 2007) and larger Lyapunov exponent (LyE) values (indicating more instability) during walking than their peers with typical development (TD) (Buzzi & Ulrich, 2004). Here we use nonlinear methods to examine the patterns that characterize gait variability as it emerges, in toddlers with TD and with DS, rather than after years of practice. We calculated Lyapunov exponent (LyE) values to assess stability of leg trajectories. We also tested the use of 3 algorithms for surrogation analysis to investigate mathematical periodicity of toddlers’ strides. Results show that toddlers’ LyE values were not different between groups or with practice and strides of both groups become more periodic with practice. The underlying control strategies are not different between groups at this point in developmental time, although control strategies do diverge between the groups by preadolescence.