Effects Of Different Degrees Of Acute Triceps Surae Fatigue On Biomechanical Performance Of Lower Limbs In The Jumping And Landing Tas

Background and Objective:Neuromuscular fatigue is a common phenomenon in sports,and the resulting abnormal movement patterns increase the risk of joint and ligament injury.Existing studies have shown that the triceps surae can buffer the impact of the ground when jumping to the ground,stabilize the lower limb joints,and contract the posterior force at the tibia to reduce the anterior cruciate ligament(ACL).The forward load plays a good protective role.However,the effect of the functional status of the triceps on the risk of ACL injury has not attracted enough attention.Whether it will increase the risk of ACL injury after fatigue is still very preliminary and needs to be further explored.In summary,this study used the repeated resistance contraction fatigue induction model of triceps surae to compare and observe the kinematics,dynamics and muscle contraction characteristics of lower limb joints in jumping landing tasks with different degrees of fatigue,and to analyze and explore the effects of different degrees of triceps surae fatigue on the risk of non-contact ACL injury.The conclusions of the study will help to further enrich the relevant theories of the risk mechanism of non-contact ACL injury,and provide some theoretical support for the development of more comprehensive and effective ACL injury prevention programs.Methods:In this study,20 healthy female college students were selected as the research objects.HUMAC isokinetic muscle strength test system was used to induce triceps surae fatigue by continuous plantar flexion resistance isokinetic contraction.Three consecutive times of failure to reach 75 %,50 % and 25 % of the maximum plantar flexion moment were regarded as mild fatigue,moderate fatigue and severe fatigue respectively.The subjects performed the jumping landing task before fatigue and after different degrees of fatigue.The Kistler three-dimensional force platform,Qualisys three-dimensional motion capture system and Noraxon surface electromyography instrument simultaneously collected the corresponding data.All the data in this study were analyzed by one-way repeated measures analysis of variance to compare the kinematic and dynamic indexes of the lower limb joints at the initial touchdown moment and the vertical ground reaction force(V-GRF)between different fatigue degrees,and the differences in the 100 ms myoelectric indexes before and after touchdown,with a significant level of P < 0.05.Results:(1)Comparison of kinematic indicators:V-GRF peak time : There were statistical differences in knee flexion angle(P =0.005)and ankle plantar flexion angle(P = 0.037)at V-GRF peak time after different degrees of fatigue of triceps surae.Further tests showed that the knee flexion angle after severe fatigue was significantly smaller than that of no fatigue(P =0.001),mild fatigue(P = 0.033)and moderate fatigue(P = 0.017).The ankle plantar flexion angle after severe fatigue was significantly greater than that without fatigue(P = 0.023)and mild fatigue(P = 0.008).(2)Comparison of kinetic indicators:Initial touchdown moment : There were statistical differences in hip extension moment(P = 0.022)and abduction moment(P = 0.022)at the initial touchdown moment after different degrees of fatigue of triceps surae.Further tests showed that the hip extension torque after mild fatigue(P = 0.027),moderate fatigue(P = 0.014)and severe fatigue(P = 0.044)of the triceps surae was significantly greater than that in the non-fatigue stage.The abduction moment of hip joint after severe fatigue(P =0.007)was significantly smaller than that without fatigue.V-GRF peak moment : There were statistical differences in hip flexion moment(P = 0.001)and knee flexion moment(P = 0.047)at the peak moment of V-GRF after different degrees of fatigue of triceps surae.After further examination,it was found that the hip flexion torque after mild fatigue(P = 0.031),moderate fatigue(P= 0.013)and severe fatigue(P = 0.01)was significantly greater than that of no fatigue stage.The flexion moment of knee joint after severe fatigue was significantly smaller than that without fatigue(P = 0.015)and mild fatigue(P = 0.034).(3)Comparison of EMG indicators:There was a statistical difference in the activation rate of hamstring muscle within 100 ms after different degrees of fatigue of triceps surae(P = 0.027).Further tests showed that the activation rate of hamstring muscle in mild fatigue(P = 0.035)was significantly higher than that in non-fatigue stage.Severe fatigue(P = 0.019)was significantly less than mild fatigue.Conclusion:(1)Different degrees of acute triceps surae fatigue have different effects on the coping strategies of lower limb joints during jumping landing : there is no significant change in the biomechanical performance of lower limb joints during mild and moderate fatigue,but after severe fatigue,the hip joint extension torque increases,the knee flexion angle and flexion torque decrease,and the ankle plantar flexion angle increases,which can lead to the biomechanical performance of ACL load increase.This suggests that there may be a threshold for the effect of triceps fatigue on the risk of ACL injury,that is,severe fatigue will lead to a higher risk of ACL injury during jumping landing.(2)After severe triceps fatigue,the activation rate of hamstring muscle decreased significantly when performing jumping landing.The lack of contraction compensation ability may be an important reason for the biomechanical performance of ACL injury in lower limb joints.