The Effect of a Secondary Cognitive Task on Lower Extremity Biomechanics During Landing

Background: The purpose of this study was to examine the effect of a cognitive task on jump-landing biomechanics and performance. Methods: 26 recreational athletes participated in the study. Participants jumped forward off of a 30cm box a distance equal to one half of their body height, then immediately performed a countermovement jump. This movement was performed in a control condition, while counting backwards by intervals of 1, and by intervals of 7. Initial knee flexion, knee range of motion, peak vertical ground reaction force (PVGRF), stance time, and jump height were calculated. Results: There were statistically significant differences in initial knee flexion (p = 0.0004), PVGRF (p = 0.031), and stance time (0.038) between the control and counting by 1 condition. There were also significant differences in knee range of motion (p = 0.049, p = 0.012) and jump height (p = 0.001, p = 0.0002) between the control and both the 1 and 7 conditions. Conclusion: This study demonstrated that the addition of a cognitive task did alter both landing biomechanics and performance. These results have implications for developing new ACL injury screening procedures to more realistically imitate a sport environment