Introduction Secondary cognitive tasks alter the mechanics of uninjured athletes when performing athletic movements. Individuals with anterior cruciate ligament (ACL) injury similarly show deficits in postural control and gait for dual-task paradigms. It is however unclear if and how secondary cognitive tasks during athletic movements influence the mechanics of athletes with ACL injury.

Materials and Methods Thus far, 15 athletes with ACL reconstruction (33 ± 14 months post-surgery; age 26 ± 5 years) performed drop vertical jumps in a randomised order with and without added cognitive tasks targeting rapid decision-making, inhibitory control, and working memory. We assessed trunk, hip, knee, and ankle mechanics during the first 100 ms of the first landing and jump height using 3D motion capture and force platforms. We analysed the motion data as complete curves using functional paired t-tests and adjusted P-values.

Results The secondary cognitive tasks significantly reduced trunk (0-100 ms), hip (18-27 ms) and knee flexion (2-62 ms), increased ankle dorsiflexion (38-43 ms), knee abduction angle (4-72 ms) and moment (54-94 ms), and increased knee (53-75 ms) and ankle (14-28 ms) power. Jump height was also reduced by 8% (mean 3 cm; P=.002).

Conclusion Initial analyses from our ongoing study show that our secondary cognitive tasks altered drop vertical jump landing mechanics and reduced the jump height of athletes with ACL injury. Many of the observed alterations have been suggested to increase ACL injury risk. Interventions are required to better prepare athletes with ACL injury for a return to cognitively demanding sporting environments.