Acute effects of unplanned and planned hop-landing training on neurocognitive function and knee biomechanics

Background: Athletes with decreased baseline neurocognitive function could experience noncontact anterior cruciate ligament (ACL) injury in unanticipated athletic situations. Many ACL injury prevention programs (IPPs) focus on improving closed-skill movements (e.g., planned landing). However, the more open-skill movements (e.g., unplanned reactive movements) required in unpredictable sports scenarios are commonly absent from ACL IPPs. Further, the acute effects of open-skill training on neurocognitive function remain unclear. Purpose: To investigate the acute effect of unplanned versus planned training on neurocognitive function and knee biomechanics associated with ACL injury risk during side-step cutting motions. Study Design: Controlled laboratory study. Methods: Thirty-two participants (16 females, 16 males) were randomly assigned to either an unplanned training group (UT-G) or a control group (CON-G). The UT-G performed unplanned hop-landing training while the CON-G performed planned hop-landing training. Neurocognitive function was evaluated by the Trail-Making-Test B (TMT-B) and Stroop color-word interference test (SCWT-Ⅲ) pre- and post-training. Three-dimensional kinematic and kinetic data of the dominant limb were collected during the unanticipated and anticipated side-step cuttings. Neurocognitive test scores and ACL injury relevant biomechanical variables were analyzed by a two-way repeated-measures ANOVA to determine the main effects of group and time, and interaction (group x time). Results: Both groups significantly improved their TMT-B and SCWT-Ⅲ scores after the training (P < .001). There were significant interactions for group and training for peak knee abduction angle during the unanticipated side-step cuttings (UT-G: pre-training, - 8.81° ± 7.23°; post- training, - 7.40° ± 7.24°; CON-G: pre-training, - 8.23° ± 9.40°; post-training, - 9.99° ± 9.83°, P = .016) and peak vertical ground reaction force (vGRF) during the anticipated side-step cuttings (UT-G: pre-training, 3.86 ± 0.59%BW; post-training, 4.08 ± 0.74%BW; CON-G: pre-training, 3.70 ± 0.62%BW; post-training, 3.34 ± 0.62%BW; P = .042). Unplanned training decreased the knee abduction angle during the unanticipated side-step cuttings, while planned training decreased vGRF during the anticipated side-step cuttings. Conclusion: Unplanned training beneficially changed the side-step cutting biomechanics associated with ACL injury in unanticipated scenarios, while planned training benefitted anticipated scenarios. Designing ACL IPPs based on the sport type (i.e., open-skill or closed-skill) may contribute to better preparation for those sports.