IMPACT VERSUS ACTIVE LOADING SPORTS AND BONE MINERAL DENSITY IN ADOLESCENT FEMALE ATHLETES

Abstract

Purpose/Hypothesis: Soccer, tennis, swimming, and weight lifting are popular activities attracting children even at very young ages. The inherent difference in the amount and type of skeletal loading between these sports is obvious. However, the extent to which the bony stresses from each sport affects bone mineral density (BMD) in adolescent females is not clear. The purpose of this study was to examine lower extremity bone mineral densities of adolescent female athletes involved in soccer, tennis, swimming, or weight lifting to determine whether the differences in bony stress inherent to each of these sports are manifested in measures of BMD. Additionally, this study sought to compare BMD values from each sport group to normative values for adult females from the World Health Organization (WHO). Number of Subjects: Seventy-eight elite level female athletes (12.82.3 years; 157.110.7 cm; 50.914.7 kg) were examined. These subjects were further divided into 29 swimmers, 19 weight lifters, 14 tennis players, and 16 soccer players each training at least 10 months per year, 5 hours per week, and with at least 3 years in their respective sport. Materials/Methods: Areal BMD (g/cm2) of the calcaneus was measured in this single session design using a peripheral dual energy x-ray absorptiometry. Pearson correlation was used to assess the association between BMD and body mass index (BMI). Between-sport differences in BMD were examined using analysis of co-variance with BMI and age as covariates while comparison to normative data from the WHO was performed using one-sample t tests. Results: BMD was significantly correlated to BMI over all subjects (P < 0.001), however, when examined by individual sport, soccer was the only group that did not show a significant correlation between BMI and BMD. Between-sport comparison of BMD showed sport type was a significant factor (F = 4.528, P = 0.006) as BMD in the soccer players was greater than the weight lifters (P < 0.016) and swimmers (P = 0.001), but was not significantly different from the tennis players (P = 0.172). Compared to adult female values equivalent to WHO norms, soccer was the only sport significantly greater than adult norms (P = 0.003) while the swimmers were significantly less (P < 0.001) and the weight lifters and tennis players were not significantly different from the WHO norms for adult women. Conclusions: Adolescent female athletes involved in soccer, a sport requiring repetitive weight bearing and vigorous impact loading, had significantly greater BMD when compared to female athletes involved in non-impact, active loading sports of swimming and weight lifting and density exceeding normative values for adult women. Clinical Relevance: Maximizing bone accrual during adolescent years of bone development may attenuate the risk of age-related bone loss in later years. Soccer presents a sport involving repetitive impact and skeletal loading. These repetitive forces appear to have a significant impact on the development of bone density in adolescent female athletes.