The effects of vision and multiple cognitive tasks on pre-landing and early landing mechanics associated with ACL...

Anterior cruciate ligament (ACL) injuries often occur during landing tasks when visual information is limited and attentional resources are divided.

This study examined how the absence of vision and multiple cognitive tasks influenced pre-landing and early landing mechanics associated with ACL loading.

Thirty-four recreationally active college students with jump-landing sports experience performed single-leg drop landings under eight conditions: vision or no vision combined with no cognitive task, backward counting, tone counting, or both cognitive tasks simultaneously.

The absence of vision delayed the timing of minimal knee flexion during the pre-landing phase. It also increased peak vertical ground reaction forces during early landing, reflecting altered preparation and impact mechanics compared with vision. Cognitive tasks generally reduced maximal knee flexion angles, and backward counting in particular lowered knee flexion at initial contact. Tone counting reduced average knee flexion angular velocity and knee flexion range of motion during the early landing phase compared with the no-task and backward-counting conditions and increased the internal knee extension moment compared with the backward-counting task. The two cognitive task condition did not exacerbate ACL loading variables and instead lowered peak vertical ground reaction forces relative to no-task trials, suggesting a conservative landing strategy under high attentional demands.

Overall, the absence of vision had a stronger influence on ACL loading-related mechanics than cognitive load. Cognitive tasks altered both sagittal and transverse plane strategies, but their effects were non-linear. These findings highlight the importance of incorporating visual constraints and secondary tasks into screening and prevention protocols to better simulate sport environments.