Comparison of Knee Muscular Strength Balance among Pre- and Post-Puberty Adolescent Swimmers: A Cross-Sectional Pilot Study

Muscular weakness and strength imbalance between the thigh muscles are considered risk factors for knee injuries. Hormonal changes, characteristic of puberty, strongly affect muscle strength; however, it is unknown whether they affect muscular strength balance. The present study aimed to compare knee flexor strength, knee extensor strength, and strength balance ratio, called the conventional ratio (CR), between prepubertal and postpubertal swimmers of both sexes. A total of 56 boys and 22 girls aged between 10 and 20 years participated in the study. Peak torque, CR, and body composition were measured using an isokinetic dynamometer and dual-energy X-ray absorptiometry, respectively. The postpubertal boys group presented significantly higher fat-free mass (p < 0.001) and lower fat mass (p = 0.001) than the prepubertal group. There were no significant differences among the female swimmers. Peak torque for both flexor and extensor muscles was significantly greater in postpubertal male (p < 0.001, both) and female swimmers (p < 0.001 and p = 0.001, respectively) than in prepubertal swimmers. The CR did not differ between the pre- and postpubertal groups. However, the mean CR values were lower than the literature recommendations, which brings attention to a higher risk of knee injuries.

Automated summary

Muscular weakness and strength imbalance in the thigh muscles are risk factors for knee injuries. Hormonal changes during puberty affect muscle strength, but their effects on muscular strength balance are unknown. This study compared knee flexor strength, knee extensor strength, and strength balance ratio between prepubertal and postpubertal swimmers of both sexes. The findings suggest that postpubertal swimmers have higher muscle mass and peak torque than prepubertal swimmers, indicating a potential higher risk of knee injuries.