Postural control still is not fully developed in infants at early school age. At this age, formerly extremely preterm infants without major neurological disorders have almost caught up to the postural control of healthy full-term subjects.

Background/Aims: To characterize the relationship between muscle function and auxology in preterm born children. Methods: Forty-five preterm born children (birth weight ≤1,500 g with mean ± SD: 1,069 ± 281 g; median of gestational age: 29 weeks; 50% multiple births) were analyzed for auxological parameters (weight, height) and muscle function at the age of 7 years. Maximal isometric grip force (MIGF) and ground reaction forces of goal-directed counter-movement jumping were measured using the Preston dynamometer and the Leonardo force plate. MIGF, peak jump force (PJF), peak jump power (PJP) and the maximal velocity of take-off (V_max) were analyzed for their relationship to perinatal risk factors and actual auxological parameters. Results: With reference to age, weight-standard deviation score (SDS) and height-SDS were lower than in the reference population. With reference to height, MIGF-SDS and PJP-SDS were lower than in reference individuals. Children with intraventricular hemorrhage (IVH) had lower PJP-SDS and V_max than children without IVH. PJP-SDS was lower than PJF-SDS in children with IVH. Conclusion: Analyses showed a discrepancy between maximal force and power due to a decline of V_max in children with IVH.