Analysis Of Biomechanical Characteristics Of Lower Limbs Of Marathon Athletes In Different Ground Methods

Objective:To analyze and summarize the characteristics of lower limb kinematics,dynamics and electromyography in different landing ways in marathon sports,in order to optimize the movement techniques of marathon athletes and reduce the excessive energy consumption caused by unreasonable movements in marathon sports,and reduce the incidence of sports injury,to give marathon athletes scientific and reasonable theoretical guidance.Methods:Thirty subjects were divided into the FFS Group,the MFS Group and the RFS group,with10 subjects in each group.The experimental instruments include the Sony Cyber-shot high-speed camera,the Kistler 9287 C three-dimensional force-measuring platform and the NORAXON surface electromyography(SEMG)tester.The recording data are analyzed by SPAS software,and the force-measuring platform data are processed by ORIGIN2020,e MG data are processed by EMG Server3.0 software for rectification,filtering and smoothing.The final data were analyzed by SPSS 22.0,Matlab and Origin 2020.Results:1.Kinematics:(1)The FFS group is compared to the MFS group,Horizontal speed MFS greater than foot touch before FFS(ES = 2.55,P <0.01),buffer time average knee angular velocity FFS is greater than MFS(ES = 1.23,P=0.004)and at pedal extension,the knee mean angular velocity of FFS is greater than MFS(ES = 4.71,P <0.01),Hip point displacement FFS is greater than MFS(ES = 1.90,P <0.01)and knee joint point displacement FFS greater than MFS(ES = 1.68,P <0.01),Hip point speed FFS greater than MFS(ES = 2.40,P <0.01).(2)FFS group compared to RFS group,During support,the center of gravity forward distance RFS is greater than RFS(ES = 1.76,P <0.01)and center of gravity during air(ES=2.20,P <0.01),angle FFS greater than RFS(ES = 2.13,P <0.01),empty time FFS slower than RFS(ES = 1.44,P <0.01),Support time RFS longer than FFS(ES = 1.96,P <0.01),Buffer time FFS is slower than RFS(ES= 1.93,P <0.01),Horizontal speed RFS before foot touch is greater than RFS(ES = 1.47,P=0.0006),the mean angular speed of the knee joint is FFS greater than RFS(ES = 2.32,P <0.01),Hip Point displacement RFS is greater than FFS(ES = 1.13,P=0.009),toe displacement RFS greater than FFS(ES = 0.19,P <0.01),swing knee peak angle RFS greater than FFS(ES = 0.83,P=0.05),Hip Point speed FFS is greater than RFS(ES = 1.89,P <0.01)has significant differences.(3)MFS group compared to RFS group,The center of gravity forward distance MFS is greater than RFS(ES = 2.26,P <0.01),lower angle MFS over RFS(ES = 1.88,P <0.01),Support time MFS over RFS(ES = 1.44,P <0.01),buffer time RFS more than MFS(ES = 1.21,P=0.005),buffer time knee average angular speed RFS greater than MFS(ES = 2.63,P <0.01),RFS is greater than MFS(ES = 1.91,P <0.01),Hip point displacement RFS is greater than FFS(ES =3.03,P <0.01),Knee point displacement RFS is greater than MFS(ES = 2.39,P <0.01),toe displacement RFS greater than MFS(ES = 0.58,P <0.01),swing knee peak angle MFS greater than RFS(ES = 1.95,P <0.01).2.Dynamics:(1)ground reaction peak FX(+)and FX(-),Fy(-),FZ axis direction are maximum FFS,RFS minimum and Fy(+(the largest RFS and minimum).(2)Reveraction impulse:X axis RFS,FFS;Y axis FFS,RFS;Z axis RFS and MFS.(3)The X-axis direction force of the ankle joint is different from the hip and knee joint,while the change trends in the Y direction force are similar.However,the peak force,joint moment and peak moment of each joint are different.3.EMG:(1)RMS: Tibial anterior muscle: FFS 8.17%,MFS 9.6%,RFS 19.91%,Inner Head:FFS 31.94%,MFS 12.5%,RFS 17.11%,Straight femoral muscle: FFS 8.56%,MFS 12.51%,RFS9.76%,Inner femoral muscle: FFS 7.09%,MFS 19.29%,RFS 13.15%,FFS: FFS 12.83%,MFS19.48%,RFS 19.94%,Biceps head: FFS 10.6%,MFS 8.33%,RFS 7.38%,Semi-tendon: FFS is13.16%,MFS 7.93%,RFS 4.02%,Gluteus large muscle: FFS is 7.65%,MFS is 10.35%,RFS and8.71%.(2)IEMG: Tibial anterior muscle: FFS 11.1%,MFS 7.66%,RFS 19.54%,Phobular muscle:FFS 24.45%,MFS 22.76%,RFS 14.47%,Straight femoral muscle: FFS 8.54%,MFS 12.88%,RFS 6.74%,Inner femoral muscle: FFS 7.32%,MFS 12.93%,RFS 9.48%,Outside femoral muscle: FFS 9.5%,MFS 17.02%,RFS 15.48%,Biceps: 8.69% FFS,MFS 7.25%,RFS 10.25%,Half-tendon: FFS 19.54%,MFS 7.76%,RFS 13.49%,Gluteus muscle: FFS is 10.87%,MFS is11.74%,RFS and 10.54%.Conclusion:(1)The maximum buffer angle of the FFS is large,strong and fast to generate forward force.However,the FFS inside and outside direction is also strong,and long periods of exercise may lead to excessive stretching of the inside and outside ligaments of the ankle joint and injury.(2)From the perspective of muscle force,the sum of IEMG of each muscle in the MFS group is smaller than that of the other two IEMG.If the most respected running technology is small step irradiation and rapid frequency,then MFS is the most economical in marathon.(3)Activation sequence in three ground modes: Group FFS: Transateral muscle,Tibial anterior muscle,Infemoral muscle,Phoentermuscle,Stratenmuscle,Biceps,Glutetes,Sem-te ndon tendon.Group MFS:Infemoral muscle,Transateral muscle,Sem-tendon tendon,Phoen termuscle,Tibial anterior muscle,Stratenmuscle,Biceps,Glutetes.Group RFS: Phoentermu scle,Tibial anterior muscle,Stratenmuscle,Sem-tendon tendon,Infemoral muscle,Tibial ant erior muscle,Transateral muscle,Glutetes.(4)The tibial premuscle in RFS contribute the most throughout the gait cycle,and the prolonged exertion of the tibial anterior muscle causes inflammation in the inner tibia,which fully demonstrates that marathon runners using RFS are prone to tibial periosteitis.In addition,RFS has a small flexion angle between the knee joint and the lower leg and the ground at the ground touch moment,and produces large braking when touching the ground,which may cause anterior cruciate ligament injury.