Anaerobic performance in 5-to 7-yr-old children of low birthweight

Purpose: This study was intended to determine whether anaerobic muscle perf ormance is deficient in 5- to 7-yr-old children of extremely low birthweigh t (ELBW, 500-999 g) and very low birthweight (VLBW, 1000-1499 g). Methods: Fourteen ELBW and 20 VLBW children were compared with 24 normal birthweight (NBW, >2500 g) term controls. Peak (PP) and mean (MP) muscle power were de termined by the Wingate anaerobic test. Bioimpedance analysis and anthropom etry were done to assess fat-free mass (FFM) and lean cross-sectional area of the thigh and calf. Results: The ELBW group had significantly lower MP a nd PP, compared with the VLBW and, in particular, with the NEW group. This lower performance was apparent also when values were corrected for total bo dy mass (MP) and FFM (MP and PP), bur not when corrected for cross-sectiona l area of thigh and calf. Conclusion: The lower anaerobic muscle performanc e in ELBW children may be partly due to their smaller muscle mass, but may also reflect a low percentage of fast-twitch muscle fibers, low muscle phos phagen content, or deficiency in motor control.