Effect Of Lunge Distance And Foot External Rotation On Knee Loading And Cruciate Ligament Strain In Badminton Players

Objective:The lunge is the most typical and frequently used footwork in badminton.Players on the field need to repeat the lunges at different distances according to the direction of the ball,which may place a high load on the knee.After the foot touches the ground,the athletes will adopt different foot external rotation degrees according to their personal habits.As the middle joint of the lower limb,the motion of the knee plays an important role in controlling the dynamic stability of the lower limb,trunk,and upper limb power chain.The cruciate ligament is also an important anatomical structure to maintain joint stability and controls normal joint movement.However,no studies have been conducted to investigate the effects of lunge distance and foot external rotation on knee loading and the cruciate ligament strain in badminton players.Therefore,this study aimed was to compare the differences in knee loading and cruciate ligament strain between 1.5 times leg length lunge and the maximal lunge,and the maximal lung and the maximal lunge with foot external rotation 20° in badminton players.The purpose of the study is to reveal the effects of lunge distance and foot external rotation on knee joint loading and cruciate ligament strain in badminton players,to provide the relevant theoretical basis for the prevention and treatment of knee injury in badminton and the guidance of badminton training.Methods:Twelve female badminton players of level 2 and above were selected for the study.MRI scans of the subjects’ dominant knee were performed before the experiment and used to construct three-dimensional skeletal model of the knee joint and the geometric center of the cruciate ligament attachment point.The study used Qualisys optical motion capture system(200Hz),high speed Dual-plane Fluoroscopic Imaging System(100Hz),Kistler three-dimensional force platform(1000Hz),and Delsys wireless surface Electromyography(2000Hz)to simultaneously collect 1.5times leg length lunge,the maximal lunge and the maximal lunge with foot external rotation 20°.Two-dimensional images,marker point trajectories,Ground reaction forces,surface EMG data of lunges were acquired.The data were further processed using Visual 3D and MATLAB software.The 3D skeletal model of the knee was aligned with the 2D fluoroscopic images to obtain the length of the cruciate ligament.Paired t-tests were used to compare 1.5 times leg length lunge with the maximal lunge,and the maximal lunge with the maximal lunge with foot external rotation 20° in knee cruciate ligament strain and differences in knee kinematic,kinetic,and muscle activation characteristics,respectively.Results:(1)Cruciate ligament strain characteristic: ACL length tended to decrease at each characteristic moment of the different lunges.1.5 times leg length lunge and maximum lunge,the maximum lunge and the maximal lunge with foot external rotation 20° at each characteristic moment of the ACL strain were not significantly different.PCL length tended to increase at each characteristic moment of different lunges.There was no significant difference between the 1.5 times leg length lunge and the maximal lunge in terms of PCL strain at touchdown time,initial impact peak time,and second impact peak time,but at the end of the cushion,the PCL elongation of the maximal lunge was increased significantly than that of the 1.5 times leg length lunge(P<0.05).There was no significant difference in the change in PCL length between the maximal lunge and the maximal lunge with foot external rotation 20° at each characteristic moment.(2)Kinematic characteristic: Compared to the 1.5 times leg length lunge,there was an increase in knee external rotation angle at the initial peak of the maximal lunge(P<0.05),an increase in knee internal rotation angle at the second impact peak(P<0.05),and an increase in knee flexion and external rotation angle at the end of the cushion(P<0.05).Compared to the maximal lunge,the maximal lunge with foot external rotation 20° significantly increased the knee internal rotation angle at the initial impact peak moment,the second impact moment,and at the end of the cushion(P<0.05),and the maximal lunge with foot external rotation 20° significantly increased the knee external rotation angle at all characteristic moments(P<0.05).(3)Kinetics characteristic: Compared to the 1.5 times leg length lunge,the initial impact peak value and mean loading rate were significantly increased in the maximal lunge(P<0.05),and there was no significant difference in the impact peak value between the maximal lunge and the maximal lunge with foot external rotation 20°.There was no significant difference in the knee moment at each characteristic moment between the 1.5 times leg length lunge and the maximal lunge.The knee extension moment at the second peak moment of impact was significantly increased in the maximal lunge compared to the maximal lunge with foot external rotation 20°(P<0.05).The maximum lunge knee external rotation moment increased significantly at the initial peak moment,the second peak moment of impact,and the end of the cushion(P<0.05).(4)Muscle activation characteristic: Compared to the 1.5 times leg length lunge,the RMS and IEMG of the lower limb muscles were significantly higher in the maximal lunge(P<0.05),and the RMS of the biceps femoris were significantly higher in the maximal lunge with foot external rotation 20° compared to the maximal lunge(P<0.05),whereas RMS of the semitendinosus muscle was smaller(P<0.05).There was no significant difference in the IEMG of the lower limb muscles between the maximal lunge and the maximal lunge with foot external rotation 20°.Conclusion:(1)The ACL and PCL coordinate and control the stability of the knee joint in the lunge,and ACL plays a major role in the early stage of landing.As the knee flexion angle increases further,the structure that constrains the stability of the sagittal plane of the knee joint gradually changes from ACL to PCL.(2)There was no significant difference in ACL strain between the two lunge distances at each characteristic moment,while the maximum lunge PCL strain was significantly greater at the end of the cushion,suggesting that the greater knee flexion angle during the cushion phase of the lunge may increase the PCL load and that athletes should avoid knees over the toes.An increase of 20° of foot external rotation at extreme lunge distance has no significant effect on cruciate ligament strain.(3)Compared to the 1.5 times leg length lunge,the maximum lunge is significantly more loaded on the knee.Compared to the maximum lunge,the maximal lunge with foot external rotation 20° is beneficial for cushioning,but it may result in higher impact loads on the knee.Therefore the maximum lunge and the maximal lunge with foot external rotation 20° may increase the risk of the knee injury to the athletes.