Predictors of Locomotor Skill Development

We will examine the relationships between training predictors, neurobehavioral moderators and locomotor skill. The primary dependent variable is locomotor function (GMFM C for crawling and GMFM E for walking). The independent variables are error, movement index, postural control, and movement variability (see Table 1) which are measured repeatedly during training sessions Months 5–18 and will be subjected to data reduction. The moderators are early spontaneous movement behavior (Month 4), cognition (Month 5 for prone and Month 9 for upright), and motivation to move (Month 5 for prone and Month 9 for upright). One model will be developed for prone locomotor skill, and a second for upright locomotor skill. The small sample size and the potential correlation among the independent variables, including the moderators, will require careful examination and interpretation of the regression models' results. The focuses will be on obtaining estimates of slopes and their 95% CIs. We will explore modeling the dependent variable and the repeated measure of the independent variables by utilizing the mixed effects modeling approach. The three moderators may be grouped mean centered (i.e., subtracting group mean value from individual measure). The moderators will be examined individually in the mixed effect models. The moderating effects will be assessed by incorporating as an interaction of moderator X each of the independent variables utilized in the mixed effect model. The magnitude and the sign of the interaction term will be assessed to explore the moderating effects of the proposed moderators. Also, when appropriate, we will employ multivariate cluster analysis algorithms and the linear discriminant analysis to explore the relationship among and between variables. The results will help us to choose the important factors for estimating predicative models linking learning strategies to locomotor skill.