Organization of leg movements in preterm infants.

This study describes and establishes baseline data of early movement in preterm infants using a sensitive and quantitative measurement system, kinematic analysis. Subjects were 10 infants born at 34 to 36 weeks gestational age. Spontaneous leg movements were videotaped, and a 10-second segment was digitized to provide kinematic data. The same infants were tested at 3 days and again at 40 weeks postgestational age. Data obtained were compared to evaluate changes with age. Results showed that all infants had organized movement as determined by high interjoint correlations and small phase lags. Movement durations were restricted at 550 and 765 msec for flexion and extension, respectively. Amplitude, velocity, pause durations, and joint angles differed among infants. Infant leg movements are highly organized synergies not disrupted by postnatal events. Differences in movements are attributed to dynamic interaction of elements in the motor control system in real and developmental time. Similar studies on high-risk or sick preterm infants may provide clues to early detection of neuromuscular dysfunction.