| Objective: The study is aim to compare the biomechanics and electrophysiology of the lower limbs and the stress and stress distribution of the Anterior cruciate ligament(ACL)between women with General joint hyperactivity(GJH)and healthy women during the Forward vertical jump(FVJ)exercise.The results will further clarify the injury mechanism and risk factors of non-contact ACL in GJH women,and provide a theoretical basis for GJH women to prevent ACL injury,have special physical training and formulate rehabilitation plans.Methods: This study recruited 14 GJH and healthy women respectively,and the healthy women are as the control group.During the study,the Vicon three-dimensional motion capture system,Kistler force platform and Noraxon surface electromyography test system were used to collect the kinematic and dynamic characteristics of hip and knee joints and the Root mean square(RMS)of pre-activation and post-activation of lower limb muscles of the two groups at the IC moment of FVJ jumping and the peak time of Vertical ground reaction force(VGRF).Based on the finite element model of the knee joint of a female,the von-Mises stress and stress distribution of ACL at the peak time of VGRF were calculated by using the three-dimensional angle of the knee joint at the peak time of VGRF as the boundary condition and the resultant force in the long axis direction of the femur as the load.Results:(1)Kinematic results: At the IC moment of FVJ jumping,the abduction angle of hip joint in GJH group(-4.51±3.71°)was lower than that in control group(-8.02±2.76°),and the valgus angle of knee joint in GJH group(-2.68±2.43°)was higher than that in control group(-0.05±2.48°),which has a verysignificant difference(P<0.05).While there was no significant difference in hip flexion angle and knee flexion angle between the two groups(P>0.05).At the peak moment of VGRF,the flexion angle of knee joint in GJH group(-36.47±7.06°)was lower than that in control group(-41.60±5.59°),and the valgus angle of knee joint in GJH group(-3.62±3.99°)was higher than that in control group(-1.44±3.35°)and the difference between them was statistically significant(P<0.05).In the buffer stage,the peak adduction angle of the hip joint in the GJH group(1.84±3.83°)was larger than that in the control group(-3.73±2.47°),and the peak valgus angle of knee joint in GJH group(-11.91±4.34°)was significantly higher than that in control group(-4.53±3.23°)(P<0.01).However,there was no significant difference in the peak flexion angle of hip joint and knee joint between the two groups(P>0.05).(2)Dynamic results: In the IC moment of FVJ jumping,there was no significant difference in hip extension torque,hip adduction torque,knee flexion torque and knee valgus torque between the two groups(P>0.05).The peak value of VGRF in GJH group(1367.78±199.52N)was significantly higher than that in control group(1090.33±250.48N)(P<0.01).In the buffer stage,the peak adduction moment of the hip joint in the GJH group(2.24±1.05Nm/kg)was significantly higher than that in the control group(1.53±0.68Nm/kg)(P<0.05),while the peak extension moment of the hip joint,the peak extension moment of the knee joint and the peak valgus moment of the knee joint were not statistically significant(P>0.05).(3)Muscle electrophysiological results: In FVJ jumping exercise,the preactivation of vastus medialis(VM)in GJH group(1.05±0.39)was higher than thatin control group(0.61±0.29),and the post-activation of VM in GJH group(1.79±0.78)was higher than that in control group(1.11±0.40),which has a very significant difference(P<0.01).The pre-activation of the lateral gastrocnemius muscle(GL)in the GJH group(0.51±0.32)was significantly different from that in the control group(1.11±0.86)(P<0.05).There was no significant differencein the post-activation of GL and the pre-activation and post-activation of vastus lateralis(VL),biceps femoris(BF),semitendinosus(SEM),gluteus medius(GMED)and medial gastrocnemius(GM)during FVJ jumping(P>0.05).(4)The stress results of ACL : At the peak time of VGRF in FVJ jumping,the von-Mises peak value of ACL in GJH group was 20.77 MPa、the peak deformation was 7.92 mm,and the von-Mises peak value of ACL in control group was 14.32 MPa、the peak deformation was 3.47 mm.The peak stress of both groups was distributed at the femoral attachment point.Conclusions:(1)GJH women in FVJ jumping,landing buffer posture appeared lower limb dynamic valgus mode,which showed a larger hip adduction angle,knee valgus angle,hip adduction torque and smaller knee flexion angle.(2)The pre-activation and post-activation of VM increased and the pre-activation of GL decreased in GJH women during FVJ jumping,indicating that the lower limb nerve control ability of GJH women was unbalanced.(3)The von-Mises stress and deformation of ACL in GJH women during FVJ jumping is greater,and the stress is mostly concentrated at the femoral attachment point,which increases the risk of ACL injury. |
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