Muscular profiles of adolescent female soccer players: a cross-sectional comparison of hamstring-to-quadriceps and vastus medialis-to-vastus lateralis characteristics.

backgroundTo characterize multifaceted muscular profiles potentially associated with knee joint sports injuries in adolescent female athletes, we compared hamstring-to-quadriceps (H:Q) ratios derived from isometric torque and isotonic power, as well as the relative muscle quality characteristics of the vastus medialis (VM) and vastus lateralis (VL), between adolescent female soccer players and recreationally active controls.

methodsIn this cross-sectional study, 97 adolescent females (soccer: n = 62; control: n = 35) were categorized into older (≥ 162 months) and younger (< 162 months) cohorts. Assessments of both legs included isometric peak torque and isotonic peak power of the knee extensors and flexors using a dynamometer, along with ultrasound-derived muscle echo intensity and shear modulus of the VM and VL at rest. The H:Q ratios were calculated from both torque and power, whereas VM:VL ratios were derived from echo intensity and shear modulus to evaluate relative muscle quality characteristics.

resultsThe isometric H:Q ratio was significantly higher in the soccer group than in the control group (pooled across age groups and legs; soccer: 55.3% ± 9.8%; control: 51.0% ± 10.4%). However, no significant between-group differences were observed in the isotonic H:Q ratio (soccer: 86.3% ± 21.1%; control: 81.4% ± 27.9%) or in the VM:VL ratios for echo intensity (soccer: 91.0% ± 10.4%; control: 91.8% ± 7.2%) and shear modulus (soccer: 84.0% ± 22.8%; control: 83.9% ± 23.2%). Furthermore, the isometric H:Q ratio showed no significant effects for age or leg dominance, whereas the isotonic H:Q ratio was significantly higher in younger participants and in the non-dominant leg.

conclusionsThese findings suggest that isometric and isotonic H:Q ratios capture distinct aspects of knee muscle function. Additionally, no significant differences were observed between elite soccer players and recreationally active peers in the isotonic H:Q ratio or ultrasound-derived VM:VL ratios, suggesting that highly trained adolescent female soccer players do not necessarily exhibit distinct dynamic power or resting muscle quality. These multifaceted muscular profiles may provide exploratory laboratory-based reference data, although longitudinal studies are needed to determine how these characteristics relate to actual injury incidence.