Sex and limb differences during a single-leg cut with body borne load.

Background: Military personnel don body borne loads that produce maladaptive lower limb biomechanics, increasing risk of musculoskeletal injury during common training tasks. Female personnel have over twice the injury risk as males, but it is unknown if a sex dimorphism in lower limb biomechanics exists during common training-related tasks.

Research Question: To determine whether lower limb biomechanics exhibited during a single-leg cut with military body borne loads differ between sexes.

Methods: Sixteen females and 20 males had lower limb biomechanics quantified during five single-leg cuts off each limb with four loads (20, 25, 30 and 35 kg). Each cut required participants run 4 m/s, before planting their foot on a force platform and cut 45° towards the opposite limb. Lower limb biomechanics related to musculoskeletal injury were submitted to a repeated measures ANOVA to test for main and interaction effects of load, sex, and limb.

Results: During the cut, load increased peak proximal anterior tibial shear force (p < 0.001) and peak hip flexion (p = 0.010) and knee abduction (p = 0.045) moments, but decreased peak knee flexion angle (p = 0.032). Females exhibited greater peak proximal anterior tibial shear (p = 0.014), and peak hip adduction (p < 0.001) and knee external rotation (p = 0.001) moment than males. Dominant limb exhibited larger peak hip adduction (p = 0.002); whereas, the non-dominant limb exhibited greater peak hip internal (p = 0.002) and knee external (p = 0.007) rotation moments. Only the non-dominant limb increased peak knee abduction moment (p = 0.001) with additional load.

Significance: During the cut, adding body borne load produced maladaptive biomechanics that may increase knee musculoskeletal injury risk. Load increased peak proximal tibial shear and potential strain of knee's soft-tissues. Females exhibited a sex dimorphism in lower limb biomechanics that may further elevate their injury risk. Both limbs exhibited biomechanics that may increase injury risk, but only the non-dominant limb further increased injury risk with load.