Permanent deficits in handgrip strength and running speed performance in low birth weight children.

Objective: The main goal of this study was to verify the influence of low birth weight (LBW) on the physical fitness of children aged 7-10 years. The comparisons were subsequently adjusted for chronological age, gender, physical activity (PA), and body composition.

Methods: A total of 356 children of both genders born in Vitoria de Santo Antão (Northeast of Brazil) were divided into two groups according to their birth weight (LBW < 2.500 g, n = 100, and normal birth weight, NBW ≥ 3.000 g and ≤ 3.999 g, n = 256). Body composition measurements included body weight, height, body mass index, triceps, and subscapular skinfolds, and body fat percentage (%BF). PA was assessed by a questionnaire. Physical fitness was assessed by handgrip strength, muscle endurance, explosive power, flexibility, agility, maximal oxygen consumption (VO(2max) ), and running speed.

Results: LBW children were shorter, lighter, had lower fat-free mass, muscle strength, and running speed but a higher VO(2max) than the NBW group. The differences in body weight (P = 0.507), height (P = 0.177), fat-free mass (P = 0.374), and VO(2max) (P = 0.312) disappeared when adjusted for covariates. The differences in right and left handgrip strength (P < 0.01) and running speed (P < 0.01) remained significant even when controlled for age, gender, height, fat-free mass, and PA.

Conclusion: This combined analysis suggests that LBW alone can be not considered as a biological determinant of growth, body composition, or physical fitness in children, but is a predictor of muscle strength and running speed.