Associations Between Bone Age, Body Composition and Physical Performance in Icelandic 12-Year-Old Female Soccer Players

Biological maturation significantly influences physical development and performance, with notable differences between sexes. Research using objective measures, such as bone age (BA) assessed with X-ray to evaluate maturity and dual-energy X-ray absorptiometry (DXA) to assess body composition, remains scarce, particularly in females. This study investigated the associations between BA, body composition and physical performance in 12-year-old female soccer players. In total, 89 players (M_age 11.89 ± 0.33 years) from ten local soccer clubs across the greater Reykjavík area participated. BA, measured with X-ray, indicated biological maturity, whereas DXA assessed body composition. Physical performance was measured with a 40-m linear sprint, the countermovement jump (CMJ) and the Yo-Yo intermittent recovery test (IR1-test). Results showed that BA had a small negative correlation with 40-m sprint time (r = −0.253, p = 0.017) but not with other performance tests. Total fat mass and fat percentage positively correlated with 40-m sprint time (r = 0.351 and r = 0.566) and negatively with CMJ height (r = −0.534 and r = −0.632) and peak power (r = −0.490 and r = −0.636; all p < 0.001). Fat-free mass and fat-free mass index were negatively correlated with 40-m sprint time (r = −0.299 and r = −0.301; both p = 0.004) but not with other tests. No body composition measures correlated with the IR1-test. These findings emphasise the importance of understanding female-specific maturation patterns and their impact on physical performance, highlighting the need for targeted research and tailored training programmes for youth female athletes.