Effects of Variable Practice on Kinematics and Accuracy of Throwing in Boys with Developmental Coordination Disorder

Many children with Developmental Coordination Disorder (DCD) cannot throw, which often prevents them from taking part in age-appropriate activities. The present research examined the degree to which variable practice, embedded in the Motor Schema Theory (Schmidt, 1975), would positively affect movement effectiveness, and coinciding accuracy, as well and parametrization of spatial and temporal aspects of control. Nine boys diagnosed with DCD (M = 10.7 years, SD = 1.0) participated in a pre-test, ten 30 minute training sessions, post-test, and a transfer test. Only pre- and post-tests involved kinematic data collection and measurement of accuracy. The variable practice involved throwing a tennis ball from a distance of 5 meters at 3 different targets (40 cm vs 35 cm vs 25 cm), positioned in three different locations. The transfer test was presented in a new environment with novel conditions. Results reveled improvement in movement effectiveness, at the group level, however when individual data was examined not all participants benefited to the same degree, especially when the transfer test was considered. All participants improved in regards to their accuracy. The changes in the outcome coincided with changes in spatial parametrization at the elbow, but not the shoulder. Also, higher velocity of the ball and angular velocity at the elbow were evident. From the clinical standpoint, the present study highlighted the importance of introducing context relevant variability in the learning program, however the decline in performance in the transfer test indicates that more research is warranted to understand the lasting effects on motor schema.