The anterior cruciate ligament (ACL) is a passive stabilizer for the knee joint, and functions to primarily restrict anterior tibial translation on the femur. Injury to the ACL is a devastating injury to endure and has become increasingly more common in youth. ACL injury not only takes an athlete out of sport in the short term, but also greatly increases the risk of accelerated osteoarthritis in the knee.Age and sex have shown to be two important determinants of ACL injury risk, as post-pubescent females are to be 2-8 times more likely to sustain a potential ACL injury compared to their male counterparts. There are hormonal and anatomical differences between age and sex groups to be considered, however biomechanical risk factors which have shown to be modifiable, need to be studied further in order to ultimately work on reducing injury risk through training interventions. While there have been studies that have identified the biomechanical profiles of age and sex groups, little research has attempted to observe the relationship between adjacent joints during a drop jump task. Therefore, the purpose of the current study was to identify differences in biomechanical patterns between sexes and age groups. It also serves to identify potential relationships between adjacent lower-limb joints during a drop jump task. Male and female athletes were recruited (male=69, female=71) from Acadia University summer camps, Acadia varsity and club sports teams, local soccer and basketball sporting clubs, as well as through word of mouth. Of the 69 males, 33 were considered pre-pubescent (age = 10.6±1.8yrs, height 148.8 ±15.0 cm, weight 40.8 ± 12.0 kg), and 36 were considered post-pubescent (age=20.6±2.1 yrs, height = 182.3 ± 6.6 cm, weight 83.2 ± 10.6 kg). Of the 71 females participating in the study, 31 were considered pre-pubescent (age=11.2 ± 1.5 yrs, height 151.3 ± 9.2 cm, weight 41.5 ± 9.1 kg), and 40 were considered post-pubescent (age= 20.1 ± 1.5 yrs, height 168.2 ± 6.9 cm, weight 69.4 ± 11.3 kg). A double-leg drop-jump protocol was employed to analyze group mean joint angles at initial contact (IC), maximum joint angles during stance, as well as joint range of motion (ROM) from IC to max. Peak joint moments for the hip, knee and ankle were also analyzed. Joint angles were calculated in the sagittal plane, with knee frontal plane joint angles also being calculated, while peak joint moments were also calculated in both the sagittal and the frontal planes. Two-way ANOVAs (p>0.05) were used to calculate age (pre vs post-pubertal) and sex (male vs female) effects as well as age by sex interaction effects. Bonferroni pairwise comparisons were used when an interaction effect was identified. It was observed that pre-pubescent individuals displayed significantly greater joint angle ROMs in all measures, while post-pubescent individuals displayed greater peak joint moments compared to pre-pubescent participants for all measures except peak knee abduction moment. It is notable that females displayed a greater peak knee abduction angle during the drop jump task. Males displayed a significantly greater peak hip extension moment, knee extension moment, ankle plantarflexion moment, and ankle supination moment, while females displayed greater hip abduction moments. Linear regression analyses show knee flexion ROM to be a significant predictor of ankle and hip ROM in pre-pubescent females, post-pubescent males, and post-pubescent females. These findings provide insight on the difference in biomechanical patterns between age groups and sexes. Future studies should continue to test the validity of using regression analyses between lower-extremity joint biomechanics during athletic movements.
