Abstract
Landing asymmetry is a risk factor for knee anterior cruciate ligament injury. The aim of this study was to identify kinetic asymmetries in healthy recreational athletes performing different jump-landing techniques. Twelve recreational athletes engaged in regular training underwent kinetic evaluation using two 3D force plates and were analyzed for: (a) three-dimensional peak forces, (b) time to peak vertical force, and (c) initial phase asymmetries. All data were collected during performance of unilateral and bilateral trials of forward and drop jump tasks. Forward jump-landing tasks elicited greater kinetic asymmetry than drop-landing tasks. Regardless of jump-landing technique, the preferred leg experienced higher forces than the non-preferred leg. The initial landing phase showed more kinetic asymmetries than the later phase when peak vertical forces occur. It was concluded that when screening athletes for kinetic asymmetries that may predispose them to injury, forward jump-landing tasks and the early landing phase might show more kinetic asymmetries than drop jump-landing tasks and the late landing phase, respectively.
Highlights
ACL injuries usually occur through a non-contact mechanism, frequent during jump-landing tasks1-5.These injuries are very common in the physically active population, and most ACL injuries require surgical treatment6,7
For unilateral forward landings (Figure 1), no statistical difference was found between legs for peak vertical [t(11)=0.672; P=0.516; effect sizes (ES)= 0.076; r= 0.038], anteroposterior [t(11)=-0.251; P=0.806; ES= 0.065], medial [t(11)=0.349; P=0.734; ES= 0.041] and lateral [t(11)=-0.50; P=0.961; ES= 0.006] ground reaction forces (GRF) force components
It was observed that both tasks elicited statistically significant leg asymmetries for peak forces, but asymmetries did not occur in the same GRF components (Figure 2)
Summary
ACL injuries usually occur through a non-contact mechanism, frequent during jump-landing tasks.These injuries are very common in the physically active population, and most ACL injuries require surgical treatment. Athletes predisposed to knee ACL injury may exhibit one or more faulty neuromuscular strategies: a) they land with excessive knee valgus, which requires higher stress on their ligaments, b) they recruit quadriceps more than hamstrings, c) they present trunk control deficits such as reduced trunk proprioception, and d) they exhibit kinetic and kinematic leg asymmetries, for example, imbalance in joint angles or forces between lower extremities. The leg dominance theory refers to the side-to-side symmetry between the lower extremities and how some athletes tend to use more one of the legs during the landing phase of jumps. ACL injury explained by the leg dominance theory may rely on leg asymmetries. Such asymmetries related to leg preference, which means the preferential use of a given leg rather than the contralateral use of legs, are still debatable
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