Context: As relatively few studies have examined landing mechanics in younger (<12 >yrs) populations, this study compared male and female youth soccer players' landing mechanics.

Objective: To test the null hypothesis that there would be no gender difference in lower extremity landing kinetics and kinematics in the landing leg.

Design: Descriptive, nonrandomized cohort study.

Setting: Controlled laboratory setting.

Patients or Other Participants: Twenty-nine (11 M, 18 F) healthy youth soccer players (11.3 ± 0.7 yrs, 150.2 ± 7.6 cm, 41.7 ± 11.2 kg) with no history of lower extremity injury.

Interventions: Subjects hung from a horizontal bar, dropped 38 cm, landing on one leg. Kinematic and kinetic data were collected to calculate joint angles and moments at the pelvis, hip, knee, and ankle. Trials were trimmed and normalized to 100 ms pre and 300 ms post initial contact. Data were averaged over 5 drop landings for each subject. A principal component analysis was performed on the waveform of all kinematic and kinetic variables. To determine gender differences, a MANOVA was performed on the scores of the extracted principal components (PC).

Main Outcome Measures: Three-dimensional pelvis, hip, knee, and ankle kinematics and kinetics.

Results: Males displayed greater pelvic flexion range of motion (Pelvis PC2: 9.83 ± 2.05 vs. 6.01 ± 1.63), pelvic rotation magnitude (Pelvis PC1: 4.14 ± 7.44 vs. -2.53 ± 6.26), and hip extension moments (Hip PC1: 15.56 ± 1.59 vs. -9.51 ± 2.39) than females. In the frontal plane, males displayed greater changes in hip abduction (Hip PC2: 10.11 ± 2.16 vs. -6.18 ± 1.44) and external rotation moments (Hip PC3: 3.31 ± 6.02 vs. -2.02 ± 5.76). Males also displayed greater knee flexion near the end of the landing (Knee kinematic PC4: 6.66 ± 5.89 vs. -4.07 ± 7.64). Males experienced greater knee moments (Knee kinetic PC3: 5.72 ± 8.27 vs. -3.50 ± 7.65) in the sagittal plane along with rapid changes in knee rotation moments (Knee kinetic PC2: 2.49 ± 4.10 vs. -1.52 ± 4.33; Knee kinetic PC4: 0.98 ± 8.95 vs. -0.61 ± 7.19) in the transverse plane compared to females. Greater flexion motions, coupled with a larger extension moments suggest males absorbed more energy in the sagittal plane. The patterning of the frontal and transverse plane moments in males appeared to be more ballistic throughout the landing phase.

Conclusions: These results support the premise that males used a different landing strategy than females, a strategy that relies on impulsive rather than gradual dissipation of energy. This strategy may become deleterious at the knee as rapid changes in knee rotation moments could cause excessive strain in the ACL, considering that there are no large muscle groups that dissipate energy in the transverse plane at the knee.