## 4 Discussion
Contrary to our hypothesis, females generated a sagittal plane net extensor LSM, while males produced a net flexor LSM (Table 1), suggesting that females landed differently than males. Both sexes produced hip flexor moments at IC (Table 2); however, male hip flexor moments were significantly larger than females, resulting in a net flexor LSM pattern at IC (Figure 2, Table 2) that would be considered unsupportive. The ankle provides support against sagittal plane collapse through an extensor (plantarflexor) moment. Females produced an ankle plantar flexor moment, while males produced a flexor (dorsiflexor) moment at IC (Table 2). Lastly, male sagittal plane knee moments were significantly greater at IC (Table 2). This finding was contrary to our hypothesis; however, in combination with the hip and ankle moments, a noticeable sex difference became apparent. Males seemingly produced less support against sagittal plane flexion collapse at IC (smaller LSMs vs. females) due to hip flexor and ankle dorsiflexor moments, despite a larger knee extensor moment. Males may possibly utilize the hip and ankle flexor moments to land with less rigidity at IC. Male LSMs subsequently became supportive (extensor) by 50 ms, so the hip-ankle flexor pattern was, in fact, short-lived and may be a sex-based landing characteristic, similar to what was noted in the frontal plane, with equally short-lived female hip adductor moments. Support against transverse plane internal rotation of the tibia relative to the femur was present for both sexes at IC, with female values being significantly greater in the 0-25\({}^{\circ}\) condition, which disproved our hypothesis. (Figure 4, Table 1). Both sexes produced hip internal rotation moments in all conditions, which would prevent external rotation of the femur on a fixed tibia (Table 2). Neither sex generated an external rotation knee moment (Table 2); therefore, there was no support from the knee that could limit internal tibial rotation relative to the femur. Overall, the knee moments failed to provide support against the transverse plane motion that is linked to injury [45]. Both sexes generated small net internal rotation ankle moments at IC (Table 2). Despite being small in magnitude, these internal rotation moments in combination with the internal rotation hip moments aide in protection of the knee. Overall, the results suggest that support against transverse plane collapse was most prominent at IC, with internal rotation hip moments providing the greatest contribution to support. The consensus regarding the investigation of mechanisms of injury, such as in non-contact ACL injury, is that all lower extremity joints and planes of motion must be considered in the analysis [49]. Movement model analyses have been limited to single planes or single joints [2, 3, 10, 35, 43, 50, 51, 52]. The LSM model [37, 38] provides a means of quantifying lower extremity support in each plane with contributions from the hip knee and ankle joints; however, the analysis is not without limitations. Measurement errors consist of those inherent to inverse dynamic calculation [7, 53, 54, 55, 56]. Furthermore, as with other investigations that utilize a deceleration movement model, the magnitude of the loads does not recreate those associated with actual ACL injuries [2; 10; 29; 37; 43; 44; 57]. A more rapid deceleration and/or fall from a greater height may result in greater moments, which could influence the kinematic and kinetic response [57; 58; 59]. However, the present data is within the range of what has been reported in publications utilizing similar movement models [44; 57]. Given the relatively small sample size of 20 healthy subjects, care must be taken with broad generalization of the results. However, our findings provide encouragement to conduct broader assessments of healthy and clinical subjects to generate clinical correlations.