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Abstract

Non-contact anterior cruciate ligament (ACL) injuries commonly occur during the early deceleration phase of one-leg landing. While the risk of ACL injury increases with concurrent cognitive demands such as attention, reaction time or inhibitory control, only a few studies have investigated the association between cognitive function and unplanned landing mechanics under the jump-and-land movement paradigm. PURPOSE: The purpose of this study was to determine the biomechanical costs of single leg landing as a function of inhibitory control applied for the selection of landing limbs. METHODS: Participants (6 females and 8 males, 23.4 ± 5.2 years) were required to perform three successive trials of countermovement jump-and-land for each foot under three different anticipation conditions (i.e., planned (P), unplanned-compatible (UP-C), and unplanned-incompatible (UP-IC)). The indication of the requested landing leg was delivered by visual cues on the screen (i.e., left or right footprint) either before in planned condition or after take-off in unplanned condition. In trials with green color footprint participants were required to land with ipsilateral limb (planned & unplanned-compatible), and land with contralateral limb in trials with red color footprint (unplanned-incompatible). The landing direction (left or right) was randomized. Ground Reaction Force (GRF) was measured by force plate and vertical GRF (vGRF) and center of pressure (COP) characteristics were compared between the conditions. RESULTS: There were no significant differences in peak vGRF and Time-to-Stabilization (TTS) between the conditions, nor the landing feet. Measures in COP variables did not exhibit the differences between the landing feet. However, landing stability measured by COP 95% ellipse area (cm2) (P = 54.9 ± 3.7 and UP-IC = 95.4 ± 14.2), COP path length (m) (P = 0.67 ± 0.03 and UP-IC = 0.75 ± 0.05), and COP mean velocity (m/s2) (P = 0.27 ± 0.01 and UP-IC = 0.30 ± 0.02) was significantly greater in UP-IC than P condition (ps < 0.05). CONCLUSION: While landing stability between P and UP-C was not significantly different, unplanned landing costs (greater values in COP measures) were associated with increased cognitive function (i.e., UP-IC). It can be inferred that the interference between cognitive and motor demands (i.e., incompatible visual stimuli) adversely affected single leg landing stability. No significant differences in time-to-stabilization (TTS) may indicate that greater postural fluctuations seem to affect only the early landing phase (e.g., ~ 3 sec), and this timeframe is sufficient for participants to regain their balance, regardless of the postural disturbances after landing. The findings from the study can help to clarify the association between cognitive function and unplanned landing stability, and its significance on the injury and performance in landing.

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