Abstract
PurposeThe purpose was to assess if variation in sagittal plane landing kinematics is associated with variation in neuromuscular activation patterns of the quadriceps-hamstrings muscle groups during drop vertical jumps (DVJ).MethodsFifty female athletes performed three DVJ. The relationship between peak knee and hip flexion angles and the amplitude of four EMG vectors was investigated with trajectory-level canonical correlation analyses over the entire time period of the landing phase. EMG vectors consisted of the {vastus medialis(VM),vastus lateralis(VL)}, {vastus medialis(VM),hamstring medialis(HM)}, {hamstring medialis(HM),hamstring lateralis(HL)} and the {vastus lateralis(VL),hamstring lateralis(HL)}. To estimate the contribution of each individual muscle, linear regressions were also conducted using one-dimensional statistical parametric mapping.ResultsThe peak knee flexion angle was significantly positively associated with the amplitudes of the {VM,HM} and {HM,HL} during the preparatory and initial contact phase and with the {VL,HL} vector during the peak loading phase (p<0.05). Small peak knee flexion angles were significantly associated with higher HM amplitudes during the preparatory and initial contact phase (p<0.001). The amplitudes of the {VM,VL} and {VL,HL} were significantly positively associated with the peak hip flexion angle during the peak loading phase (p<0.05). Small peak hip flexion angles were significantly associated with higher VL amplitudes during the peak loading phase (p = 0.001). Higher external knee abduction and flexion moments were found in participants landing with less flexed knee and hip joints (p<0.001).ConclusionThis study demonstrated clear associations between neuromuscular activation patterns and landing kinematics in the sagittal plane during specific parts of the landing. These findings have indicated that an erect landing pattern, characterized by less hip and knee flexion, was significantly associated with an increased medial and posterior neuromuscular activation (dominant hamstrings medialis activity) during the preparatory and initial contact phase and an increased lateral neuromuscular activation (dominant vastus lateralis activity) during the peak loading phase.
Highlights
Anterior cruciate ligament (ACL) injuries are very common during dynamic sports activities in the active population (16–39 years) accounting for approximately 26% of all internal knee injuries [1]
The peak knee flexion angle was significantly positively associated with the amplitudes of the {vastus medialis (VM),hamstring medialis (HM)} and {HM,hamstring lateralis (HL)} during the preparatory and initial contact phase and with the {vastus lateralis (VL), HL} vector during the peak loading phase (p
Small peak knee flexion angles were significantly associated with higher HM amplitudes during the preparatory and initial contact phase (p
Summary
Anterior cruciate ligament (ACL) injuries are very common during dynamic sports activities in the active population (16–39 years) accounting for approximately 26% of all internal knee injuries [1]. A prospective study by Hewett et al [6] has shown that high knee abduction moments during landing of drop vertical jumps (DVJ) increase ACL injury risk. A more erect landing pattern, characterized by more extended knee, hip and trunk positions, increases the vertical ground reaction force [6], external knee flexion moment [7], external knee abduction moment [8,9] and the anterior tibial shear force [10], all of which might be risk factors for ACL injury [11]. Blackburn et al [12] have shown that peak knee and hip flexion angles during landing, two easy to measure parameters, influence the kinetics at the hip and knee joints resulting in a higher injury risk. Intervention studies have shown that a combination of strengthening exercises, proximal control exercises and exercises that improve the landing pattern (such as a more flexed landing pattern) can reduce ACL injury risk [15,16]
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