Ankle Movements During Supine Kicking in Infants Born Preterm

BACKGROUND: Knowledge of musculoskeletal factors that influence supine kicking of infants born preterm has implications for early intervention. HYPOTHESES: Differences exist between infants born preterm and full-term in ankle kinematics during supine kicking, which are attributable to passive measures of the gastrocnemius/soleus (g/s) muscle tendon unit (MTU). SUBJECTS: Twenty infants born full-term and 22 born preterm were measured at term, 6 weeks, and 12 weeks of age. OUTCOME MEASURES: Ankle kinematics during supine kicking and g/s MTU length. RESULTS: Infants born preterm demonstrated less dorsiflexion, more plantar flexion, and more total ankle range during supine kicking. Gestational age explained 69% to 85% of the variability in MTU length from term to 12 weeks of age. MTU lengths explained 0% to 42% of the variance in ankle kinematics. CONCLUSIONS: Passive measures of the g/s MTU may inform clinicians about ankle kinematics in newborns to 12-week infants during supine kicking.