Reference centile curves for screening body mass index and body postural stability in football players aged 8-18 years

Introduction and purpose: Since birth, children grow up in terms of height and body weight, and subsequently in terms of the maturation of the nervous, endocrine, muscular, and cardiovascular systems. These adaptations lead to alterations in neuromuscular performances (3). The increase of body mass index (BMI) can cause a reduction in the postural stability and then increase the risk of falls, particularly when combined with low muscular mass which can generate biomechanical failure of muscular responses and loss of stability mechanisms (2). The aim of this study was to analyse the body mass index (BMI) and body postural stability (BPS) in football players across childhood and adolescence, thus developing reference centile curves, and to investigate their relationship. Methods: 512 males from 8 to 18 years were recruited from Italian football teams. It was performed a cross-sectional study. BMI was calculated measuring height and weight [body mass (kg) / height (m2)]. BPS were taken by means of a Libra seesaw balance board. Reference centile curves were created by lambda-mu-sigma (LMS) method. To assess the difference among ages, Kruskal Wallis test was performed. The correlation between BMI and BPS was evaluated by Pearson correlation coefficient controlled by age (partial correlation). In addition, a stepwise multiple regression analysis was used to determine the effect of age and BMI on BPS, and the effect of age and BPS on BMI. Finally, Pearson correlation coefficient or Sperman Rho were performed in order to detect the correlation between BMI and BPS in each age group. The assumption of normal data distribution was verified by Shapiro-Wilks’ Normality test. Results: Significant improvement in BMI (χ2(1,10)=106.383, p<0.001) and BPS (χ2(1,10)=272.141, p<0.001) were found across age. Significant partial correlation (r = 0.304; p < 0.001) was found between BMI and BPS. The multiple regression revealed that age and BMI accounted for 47.5% and 4.8% of the variance of BPS (F(2,510)=208.092, p<0.001), respectively, and age and BPS accounted for 18.8% and 7.5% of the variance of BMI (F(2,510)=90.915, p<0.001), respectively. Finally, the correlation were significant in each age group (r>0.251, p<0.05) except for football players of 11, 14, and 15 years old. Conclusion: The football players increase BMI and improve their BPS during the growth. The reference centile curves provided in this study could help trainers to assess the levels of their football players. Previous studies found that the accumulation of fat tissue can reduce postural stability and contribute towards falls (1). Accordingly, we found a direct relationship between BPS and BMI across childhood and adolescence. The lower is the BMI, the better is the body postural stability during the growth, because high BMI demands more neuromuscular control to maintain postural stability (1). However, our results showed improvements on BMI and BPS were mostly affected by the body development during growth and barely affected by their relationship. A greater limitation of this investigation is that this study have a cross sectional design. Future longitudinal study is needed to better investigate this topic. References 1. Greve, J., Alonso, A., Bordini, A.C.P.G., & Camanho, G.L.. Correlation between Body Mass Index and Postural Balance. Clinics 62, 717–20 (2007). 2. Maffiuletti, N.A., Agosti, F., Proietti, M., Riva, D., Resnik, M., Lafortuna, C.L., & Sartorio, A. Postural Instability of Extremely Obese Individuals Improves after a Body Weight Reduction Program Entailing Specific Balance Training. Journal of Endocrinological Investigation 28, 2–7 (2005). 3. Roemmich, J. N. & Rogol, A. D. Physiology of growth and development. Its relationship to performance in the young athlete. Clinics in Sports Medicine 14, 483–502 (1995).