Dual Tasking May Increase ACL Injury Risk By Decreasing Knee Flexion Angle During Jump Landing

Abstract

Non-contact anterior cruciate ligament (ACL) injuries are common among young athletes playing team sports. They must coordinate cognitive and motor processes to adapt an appropriate response to visual stimuli. It is unclear how divided attention to distractors impacts landing mechanics and ACL injury risk factors. PURPOSE: To investigate effects of dual tasking on ACL injury risk factors during jump landing using the Eriksen Flanker task. METHODS: Fourteen healthy females (age: 21 ± 2 years, mass: 64 ± 7 kg, height: 1.7 ± 0.1 m) participated in the study. They stood on a portable force platform (28 cm tall), jumped diagonally at a 60° angle to their right, landed on two in-ground force platforms and performed a second jump to their right or left at a 60° angle. The direction of the second jump appeared on a screen in front of the participant. The signal was either shown before movement (baseline) or during the flight phase of the first jump (dual task). The signal for the dual task conditions showed five arrows and participants jumped in the direction of the middle one. The four other arrows either pointed to the same direction as the middle arrow (congruent) or in the opposite direction (incongruent). Knee flexion angles, knee valgus angles, and external knee valgus moments were determined during the first 100 ms of landing. Repeated measures ANOVA was used to test for main effects of jump direction, dual task condition and interactions. RESULTS: There were significant main effects of jump direction, dual task condition, and their interaction for initial and peak knee flexion angles (p ≤ 0.009). Initial knee flexion angle (10.5 ± 5.1°vs. 14.5 ± 6.6°, p = 0.01) and peak knee flexion angle (56.2 ± 5.1° vs. 60.3 ± 5.9°, p = 0.003) were significantly lower during dual tasking when jumping to the right. There were no significant differences between the congruent and incongruent dual tasks or when jumping to the left. CONCLUSION: Initial and peak knee flexion angles were decreased when the visual stimuli was presented mid-flight rather than at the beginning of the jump when jumping to the right (lateral to the knee). However, the incongruent Flanker task did not significantly affect knee flexion angle. Further research focusing on mid-flight decision making with a more challenging incongruent visual stimuli that mimics dynamic team sports is merited.