Factors Predictive of Musculoskeletal Health in Male and Female Adolescent Middle Distance Runners

Abstract

1083 Few gender comparisons are available on musculoskeletal adaptations of adolescents within the same sport. PURPOSE: The purpose of the study was two fold; (1) to compare bone mineral and bone geometric properties in male (N = 20, age = 16.8 ± 0.6, mean ± SD) and female (N = 20, age = 16 ± .01, mean ± SD) elite level adolescent middle distance runners with the same number of age and gender-matched controls (males age = 16.4 ± .07, females age = 15.8 ± .02) and (2) to examine gender differences in factors predictive of bone mineral content (BMC) between elite level adolescent runners. METHODS: Total body and regional BMC and body composition values were obtained using Dual X-ray Absorptiometry. Bone and muscle geometry of the distal third tibia were acquired from 3mm contiguous slices using Magnetic Resonance Imaging. Strong correlates of BMC and bone geometry were entered into multiple linear regression equations for each gender. RESULTS: Male athletes and controls differed in body mass (64.4 ± 6.2 vs 75.4 ± 14.7, p = 0.005), fat mass (5.6 ± 2.4 vs 16.5 ± 10.7, p = 0.001), BMI (20.68 ± 1.6 vs 23.8 ± 3.5, p = 0.001) and hours of physical activity per week (14.1 ± 5.7 vs 2.2 ± 0.7, p = 0.001). Absolute values in tibial bone and muscle cross-sectional areas (CSA) did not differ between the two male groups. Regional differences in BMC per kg of fat mass were greater for male athletes than their controls at the lumbar spine (p = 0.001), dominant proximal femur (p = 0.001) and dominant leg (p = 0.03). Lean mass and fat mass explained 72% variance in total body BMC. Female athletes and their controls differed in body mass (52.2 ± 6.1 vs 58.7 ± 10.8, p = 0.027), BMI (18.7 ± 1.5 vs 22.2 ± 4.2, p = 0.002), fat mass (8.2 ± 2.8 vs 19.5 ± 8.4, p = 0.001), lean mass (41.8 ± 4.3 vs 36.3 ± 3.2, p = 0.001) and hours of physical activity per week (8.9 ± 4.1 vs 2 ± 0.7, p = 0.001). Geometric differences between female athletes and their controls were evident in tibial cortical area (p = 0.003) and medullary cavity (p = 0.035) CSA. Total muscle (p = 0.35) and dorsiflexor muscle (p = 0.21) CSA at the mid distal tibia was greater in female athletes than controls. Regional differences in BMC per kg of fat mass were greater for female athletes than controls at the total body (p = 0.001), dominant proximal femur (p = 0.001) and dominant leg (p = 0.001). Similar to males, lean mass and fat mass explained the greatest amount (65%) of the variance in total body BMC. CONCLUSION: Osteogenic advantages at regional sites were greater in athletes than controls. Similar predictors of total body BMC were found between male and female athletes but geometric differences between athletes and controls were more evident among females than males. Supported by NSW Sporting Injuries Committee