Skeletal maturation, dietary intake and igf-1 in elite gymnasts aged 9-17 years

Introduction

It has been well documented that gymnastics is a sport characterized by involvement at an early age [1]. Young gymnasts performing high intensity are exposed to high levels of psychological stress and intense physical training and a caloric deficit. These factors can contribute to the delay in skeletal maturation and pubertal development and lower circulating IGF-1 levels in male and female adolescent athletes [2]. Nevertheless, there is no information in the literature referring to the gender-related difference of skeletal maturation, dietary intake and IGF-1 in elite gymnasts. The purpose of the study, therefore, was to assess difference of skeletal maturity, dietary intake and IGF-1 between male and female gymnasts aged 9-17 years.

Methods

Subjects included 89 gymnasts (45 boys and 44 girls) aged 9-17 years. All the gymnasts were characterized as being highly competitive and trained 5 days a week, 3 hours a day. The study was performed during their preparation for an upcoming racing season. Skeletal maturation was assess by TW2 [3]. Baseline dietary intake was evaluated from three randomly assigned days of diet records, including one weekend day and two weekdays. All subjects completed a three day diet record. From these records, average daily intakes of the nutrients were estimated using Computer Aided Nutritional Analysis Program. Blood samples were drawn in the morning after a 12-h fast and were spun at 3000rpm, at 4C for 20min. The serum was separated and stored at -700C. IGF was extracted from IGFBPs using the acid-ethanol extraction method. Serum IGF-1 concentrations were determined by a two-site immunoradiometric assay (IRMA) using the DSL-5600 Active Kit.

Results

The results of the study showed that there is significant difference (p < 0.01) for RUS score between male and female gymnasts. Higher mean values of RUS score were found for female gymnasts (592.0) than male gymnasts (430.2). Significant difference can also be observed for dietary intakes between male and female gymnasts except for calcium. Male gymnasts had higher mean values for dietary intakes than those of female gymnasts. Although no significant difference was found for serum IGF-1 between the groups there is significant difference (p < 0.05) for growth hormone (GH) between male and female gymnasts.

Discussion / Conclusions

In accord with previous studies, we found that elite gymnasts exhibit a specific pattern of growth characterized by a marked delay in skeletal maturation [1]. As we expected, male gymnasts had significantly higher mean energy, iron and zinc intakes than female gymnasts (p < 0.05). These data provide evidence that female gymnasts were aware of their daily body weight, took extreme care regarding low-caloric food products, were knowledgeable about the nutritional components of their daily diet [4]. Although several studies have reported a marked decrease in serum IGF-1 relative to swimmers and members of a nonathletic control group [5], no detectable differences were found between the groups in the present study. Further studies are required to examine the long-term effects of gymnastics training on circulating growth factors.

References

[1]. Claessens AL. et al. (1992). Med Sci Sports Exercise, 24:755-763.
[2]. Daly RM. et al. (1998). Eur J Appl Physiol, 79:74-81.
[3]. Tanner JM. et al. (1983). Assessment of skeletal maturity and prediction of adult height (TW2 method). London:Academic Press.
[4]. Fogelholm M. et al. (2000). Med Sci Sports Exercise, 32:738-746.
[5]. Bass S. et al. (2000). J Pediatr, 136:149-155.