INTRODUCTION
Nature of the Problem
Cerebral palsy (CP) is a motor disorder caused by a nonprogressive injury to the developing brain.1 The injury occurs perinatally and, though causes are rarely known,2,3 CP is common in infants born preterm with small birth weights.4 CP occurs in 2 to 3 of every 1000 live births5 and has heterogeneous symptoms, anatomic involvement, and functional impairment, including lifelong changes in motor function.1,2 These alterations stem from both changes in the neural drive to muscles6 and changes to muscles themselves.