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Advances in medical technology, perinatal care, and neonatal intensive care have greatly increased the rate of survival for neonates born with a variety of medical problems and very low birth weights. The majority survive relatively sequelae free, although evidence still indicates that they remain at higher than normal risk for physical, mental, and social development. As the number of medical complications increases and birthweight decreases, the expectations for normal development become less promising. The kinds of stimulation the early postnatal environment provides have been identified as important factors in the infant’s growth and development. The effects of providing patterned stimulation to infants in the neonatal intensive care unit have been investigated by many. Despite difficulties in comparing studies due to the variability of subjects used, and type, intensity, and duration of treatment, the overwhelming evidence indicates beneficial effects.

The purpose of this study was to examine the dynamic stability of two groups of children with different dynamic resources in changing contexts. The stability of the lower extremity segments of preadolescent children (8–10 years old) with and without Down syndrome (DS) was evaluated as children walked on a motorized treadmill at varying speeds. Tools from nonlinear dynamics, maximum Lyapunov exponent, and approximate entropy were used to assess the behavioral stability of segmental angular displacements of the thigh, shank, and foot. Our results suggest that children with DS show decreased dynamic stability during walking in all segments and that this might be a consequence of inherently different subsystem constraints between these groups. Differences between groups also varied, though not uniformly, with speed, suggesting that inherent differences could further constrain the behavioral response to changing task demands.

Due to increased metabolic demands during walking, ∼50% of children with myelomeningocele transition to wheelchair use during adolescence/early adulthood. The purpose of our pilot study involving children with myelomeningocele was to determine: (a) energy expenditure needs during acute use of common assistive devices and (b) if walking poles are a feasible assistive device. Oxygen uptake was recorded for eight (5–12 years old) children in four conditions: independent, walker, crutches, and poles. Acute pole use did not significantly differ from independent walking net energy consumption or cost. Participants consumed more energy while walking with the walker than independently. Our pilot results suggest that (a) acute use of common assistive devices while walking increases energy consumption and cost versus independent and (b) poles are feasible assistive devices, resulting in slightly increased energy requirements. Poles may have provided “just enough” support with minimal change in energy requirements for our participants and, with practice, may enable children with myelomeningocele to remain community ambulators.

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.