the door for investigation of possible neurophysiological explanations for the improved performance measured in motor-learning studies. Concurrently, in Russia, Bernstein2 began his work on motor control, but the work was not translated into English until the 1970s. Yet a third related area developed in the 1930s— motor development. An area of study that is very familiar to those in pediatric rehabilitation, motor development deals with how motor skills are acquired and progress during maturation. After World War II, the Army and Air Force became interested in the field of motor learning and committed scientific and financial resources to study optimal methods to train troops for high-quality and efficient performance of military duties.