Birth weight and physical ability in 5- to 8-yr-old healthy children born prematurely

Recent advances in perinatal care have resulted in increased survival rates of extremely small and immature newborns. This has resulted in some neurodevelopmental impairment. The purpose of this study was to quantitatively evaluate and compare neuromuscular performance in children born prematurely at various levels of subnormal birth weight (BW). Subjects were 5- to 8-yr-old children born prematurely at different levels of subnormal BW (535-1760 g, N = 22, PM), and age-matched controls born at full term (>2500 g, N = 15, CON). None of the subjects had any clinically defined neuromuscular disabilities. Body mass (BM) of PM was lower than that of CON (18.3 ± 2.7 vs 21.7 ± 3.8 kg) with no difference in height or sum of 4 skinfolds. Peak mechanical power output determined with a 15-s modified Wingate Anaerobic Test and corrected for BM was lower (P = 0.07) in PM than in CON (5.11 ± 1.07 vs 5.94 ± 1.00 W·kg^-1). This was especially noticeable in children born at extremely low BW (ELBW, < 1000 g. 4.49 ± 1.04 W·kg^-1, P < 0.01). Peak power, determined in a force-plate vertical jump, corrected for BM was lower in PM vs CON (25.5 ± 5.4 vs 30.8 ± 5.2 W·kg^{- 1}, respectively P = 0.01), especially in the ELBW group (20.0 ± 5.5 W·kg^{- 1}). Similarly, the elapsed time between peak velocity and actual jump take- off was longer in PM than in CON (41.2 ± 9.4 vs 35.8 ± 5.8 ms, respectively, P = 0.04). No differences were observed in peak force. The results suggest that performance deficiencies of prematurely-born children may be a result of inferior inter-muscular coordination. The precise neuromotor factors responsible for this should be identified by future research.