Kinematic characteristics of infant leg movements produced across a full day.

INTRODUCTION: Our purpose is to directly measure variability in infant leg movement behavior in the natural environment across a full day. We recently we created an algorithm to identify an infant-produced leg movement from full-day wearable sensor data from infants with typical development between 1 and 12 months of age. Here we report the kinematic characteristics of their leg movements produced across a full day.

METHODS: Wearable sensor data were collected from 12 infants with typical development for 8-13 hours per day. A wearable sensor was attached to each ankle, and recorded tri-axial accelerometer and gyroscope measurements at 20Hz. We determined the duration, average acceleration, and peak acceleration of each leg movement, and classified its type (unilateral, bilateral synchronous, bilateral asynchronous).

RESULTS: There was a range of leg movement duration (0.23-0.33 s) and acceleration (average 1.59 to 3.88 m/s2 , peak 3.10 to 8.83 m/s2 ) values produced by infants across visits. Infants predominantly produced unilateral and asynchronous bilateral movements. Our results collected across a full day are generally comparable to kinematic measures obtained by other measurement tools across short periods of time.

CONCLUSION: Our results describe variable full-day kinematics of leg movements across infancy in a natural environment. These data create a reference standard for the future comparison of infants at risk for developmental delay.