Infant intralimb coordination and torque production: Influence of prematurity

The purpose of this study is to investigate changes in leg joint coordination, intersegmental dynamics, and their relation in infants born preterm (PT) during the first months of life. Kicking actions were analyzed of 11 infants born PT at 6 and 15-weeks corrected age (CA) using three-dimensional kinematics and kinetics; results were compared to the kicking actions of 10 infants born full-term (FT). Both groups changed from a predominately in-phase coordination at 6-weeks CA to a less in-phase coordination at 15-weeks CA, however, at 6-weeks CA, infants born PT demonstrated less in-phase coordination of their ankle joints with their hip and knee joints. Between groups and across ages, both groups demonstrated consistent net and partitioned joint torque profiles, however, at 6-weeks CA infants born PT demonstrated more complex patterns of torque components. In both groups, less in-phase hip-knee coordination was associated with reduced active knee muscle torque and increased passive knee torques, however, passive knee torques had a greater influence on the kicks of infants born PT at 6-weeks CA. At 6-weeks CA, infants born PT, compared to FT, generated kicks with less in-phase hip-knee coordination, hip excursion, hip angular velocity, and hip muscle torque impulse. By 15-weeks CA, differences resolved in all variables except hip muscle torque impulse. These results highlight a different trajectory of leg joint coordination and torque production for infants born PT compared to FT.