Developmental profiles of spontaneous movements in infants.

Spontaneous movements were observed for 1-h sessions in each of 50 normal full-term infants aged from 2 weeks to 50 weeks in their own homes using videoanalysis. Movements were categorised according to the classifications of Thelen [17] and Hopkins and Prechtl [10]. Developmental profiles for the frequency of occurrence of the different types of movements were determined. These were found to be dependent on the posture and mobility (P < 0.05) of the infant. Developmental profiles for infants up to 6 months of age were also produced for the temporal characteristics of leg kicks and arm waves. The speed of the flexion and extension phases of both arm waves and leg kicks were found to increase significantly (P < 0.05), with a corresponding decrease in variability over age (P < 0.05). These developmental profiles may be useful in determining normal and abnormal motor behaviour in early infancy.