| Objective: Weightlifters carry out high-intensity training for a long time,and the waist needs to bear a huge load,and the lumbar spine as an important part of the body,whether it is for people’s health,or sports performance play a decisive role.If the waist is damaged during training,but not treated promptly and thoroughly,it may gradually turn into a chronic injury and leave sequelae.Therefore,it is necessary to pay attention to the waist health level of weightlifters,take effective measures to prevent and reduce the occurrence of waist and back injuries.Methods: In this study,the methods of kinematics and dynamics combined with finite element simulation were used to reveal the biomechanical changes of lower lumbar vertebrae and soft tissues under different hard pulls.The kinematics and dynamics data of 8 subjects were collected when they performed dedlift,stiff-legged dedlift and trap bar deadlift.The motion analysis software was used to analyze and process the data combined with human link parameters,and the lumbar joint flexion Angle,joint moment and vertical load were obtained as the boundary conditions and loads for further finite element analysis.The CT image of a weightlifter was used to establish a three-dimensional finite element model of lumbar joint.The kinematic and dynamic parameters of lumbar peak moment were loaded into the finite element model to analyze the Von Mises stress and its distribution characteristics of vertebra,cancellous bone,intervertebral disc and nucleus pulposus during hard pull.To compare the biomechanical characteristics of lumbar joint structure under dedlift,stiff-legged dedlift and trap bar deadlift.Results:In the complete lifting phase,the average range of motion of the lumbar spine joint in the sagittal plane was about 58° for the conventional dedlift;about 90° for the stiff-legged dedlift;and about 55° for the trap bar deadlift,with the largest peak moment of 891 N-m for the stiff-legged dedlif,the larger peak moment of 747 N-m for the conventional dedlift and the smallest peak moment of 639 N-m for the trap bar deadlift.(the significance level of the difference between the peak moments of the three Barbell hard pull movements was at P < 0.05).The Von Mises stress distribution characteristics on the finite element model of the lumbar spine were similar at this moment,with higher Von Mises stresses on both sides of the vertebral body and the posterior side than on the anterior side of the vertebral body,and the Von Mises stresses on each lumbar vertebral body were transmitted from top to bottom,showing a trend of first increasing,then decreasing,and then increasing.The Von Mise stress was mainly concentrated at the posterior and inferior margin of the vertebral body and the pedicle,and the maximum Von Mises stress was concentrated at the posterior and inferior margin of the L5 vertebral body.The maximum Von Mises stress on the lumbar spine was 997 MPa when the straight leg was hard pulled,which was higher than that when the traditional and hexagonal barbell were hard pulled.Subsequently,the maximum Von Mises stress in the lumbar spine was 815 MPa in the traditional hard pull.The minimum Von Mises stress on the lumbar spine was 701 MPa when hexagonal barbell was hard pulled(the significant level of difference between the three kinds of hard pulled maximum Von Mises stress was P < 0.05).Von Mises stress in cancellous bone was concentrated in the middle of L1,L2,L3 and L4,and Von Mises in L5 was distributed in the front,left and right sides of the cancellous bone,and the Von Mises stress in each cancellous bone increased first and then decreased from top to bottom,and then increased and then decreased.Von Mises stress of L1-2,L2-3 and L3-4 was concentrated around the lumbar disc,while Von Mises stress of L4-5 was concentrated at the anterior and posterior side of the lumbar disc,and the stress increased gradually from top to bottom throughout the lumbar disc.Von Mises stress on nucleus pulposus L1-2 and L2-3 was concentrated at the lower margin of posterior nucleus pulposus,Von Mises stress on nucleus pulposus L3-4 was concentrated at the upper margin of posterior nucleus pulposus,Von Mises stress on nucleus pulposus L4-5 was concentrated at the lower margin of anterior nucleus pulposus,and Von Mise stress decreased gradually from top to bottom.But it increases slightly at the bottom.Conclusions:(1)Under normal physiological function,the lumbar peak moment represents the maximum force output produced by the muscles,and the maximum force output produced by the lumbar muscles is proportional to the magnitude of the lumbar stress.In this experiment,the magnitude of the peak moment of the lumbar region in the three hard pulling movements were in the order of stiff-legged dedlift、dedlift and、trap bar deadlift,indicating that the stress in the lumbar region was greatest in the stiff-legged dedlift compared with the dedlift and trap bar deadlift,and the stress in the lumbar region was least in the trap bar deadlift,and the risk of lumbar injury was lowest in this way of barbell hard pull.(2)The cortical bone of the lumbar spine is the main part of the lumbar bearing capacity.When bearing a large extension moment,the posterior part of the vertebral body L2 and L5 and the pedicle have stress concentration phenomenon.Long-term and repeated high stress stimulation may cause fine fracture.The greatest stress of lumbar intervertebral disc is concentrated in the intervertebral disc L4-5,which is the most prone to injury and strain.(3)With the same weight and same hard pull,the stress of lumbar vertebra and lumbar intervertebral disc at different levels was different.The stress of lumbar vertebra L1 to L5 increased first,then decreased,and then increased.The stress of lumbar intervertebral disc L1 to L4-5 showed an increasing trend from top to bottom.Under the same weight and different hard pull,the lumbar vertebra and lumbar intervertebral disc under the stiff-legged dedlift suffered the greatest stress,followed by the traditional hard pull,the trap bar deadlift under the least stress. |
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