Breast Support Alters Trunk And Knee Joint Biomechanics During Double Limb Landing

Abstract

Female athletes have a greater prevalence of traumatic knee injury than male athletes. Sex-based differences in injury rates emerge with maturation and the development of sex-specific traits including breast development. Breast support is known to alter trunk biomechanics during running tasks while in landing trunk orientation has been shown to mediate ACL strain. However, the effect of breast support on knee joint biomechanics has not been previously investigated. PURPOSE: To examine the effects of breast support on trunk and knee joint biomechanics during double limb landing. METHODS: Fourteen female collegiate athletes performed five double-limb landing trials in each of three sports bra conditions: no support, low support, and high support. Three-dimensional kinematics (240 Hz, Qualisys) and ground reaction forces (1200 Hz, AMTI Inc.) were recorded simultaneously. Visual 3D (C-Motion Inc.) was used to calculate peak trunk segment angles as well as peak knee joint angles and extension moments. A repeated measures ANCOVA with post-hoc pairwise comparisons were used to evaluate the effect of breast support on knee biomechanics. RESULTS: Increasing levels of breast support were associated with reductions in peak knee flexion (p = 0.008), peak knee valgus angles (p = 0.011) and peak knee valgus moments (p = 0.033) while there were no changes in peak knee moments (p = 0.216). Trunk flexion at initial contact (p = 0.024) and peak trunk flexion (p = 0.002) increased in response to greater breast support. CONCLUSIONS: The current data revealed a multi-joint mechanical adaptation in response to lower levels of breast support. These altered biomechanical patterns are consistent with a greater risk of traumatic knee injury including ACL rupture.