Effect of mid-flight trunk motion on landing mechanics

Davis, Daniel
ACL injuries are highly prevalent and problematic in day-to-day life, and especially in an athletic domain. Often ACL tears occur when the athlete lands in a non-vertical position, rendering them unable to utilize both legs symmetrically in landing. This subsequently increases the ACL load of the landing leg, which is at least a partial cause of the injury. Mid-flight trunk motion may cause athletes to land in this non-vertical position. The goal of the current study was to analyze the effect of mid-flight medial-lateral trunk motion on Center of Mass (COM) distribution and subsequent landing mechanics. Forty-one recreational athletes (18 males and 23 females) participated. Forty-four markers were placed on each participant's body and were tracked using 3D cameras. Peak Vertical Ground Reaction Force (VGRF) was measured with two force plates. Participants were instructed to jump vertically, reach straight up, left, or right, and land naturally. Each medial-lateral reach condition (left or right) produced asymmetric landing between legs, with the leg ipsilateral to reach direction landing first (mean difference of 14.0 ms reaching left and 16.7 ms reaching right). Peak VGRF was also greater for the ipsilateral leg in these conditions (2.6 times body weight for both left and right reaching conditions) compared to the contralateral leg (1.7 times body weight). These results indicate that mid-flight trunk motion can cause athletes to land in a non-vertical position, placing more stress on the leg ipsilateral to the reach direction, and increasing their risk of ACL injury in that leg.
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