Effect Of Specific-fatigue Protocol On Kinematics Of High-risk Maneuvers Related To ACL Injury For Soccer Players

Objective:Soccer is an intermittent sport with high-intensity,long-term and multi-direction characteristics.The decline of neuromuscular function post-fatigue is an important risk factor to cause Anterior Cruciate Ligament（ACL）injury.The purpose of the study is to explore the effects of trunk and lower limb kinematics related to ACL injury pre-post soccer-specific fatigue.Methods:Seventeen soccer athletes were recruited to participate soccer-specific aerobic fitness test(SAFT⁹⁰).3D motion capture system（Nokov）was used to collect kinematic of single-leg drop jump（35cm）and side-cutting pre-post fatigue.Cortex-64 5.5.0 software was used to identify and process the kinematic data.2×2 repeated measurement of two-way ANOVA was used to identify the effect of fatigue and task on trunk and lower limb kinematics.Results:（1）Knee adduction-abduction Angle(F^[1,15]=5.683,p=0.031,η_p²=0.275)had significant interaction effect on fatigue and task at the initial contact.Side-cutting showed a larger angle of knee abduction Angle（p=0.017,d=0.58）at the post-fatigue.（2）At the initial contact,the athlete showed a smaller trunk tilt angle（p=0.043,η_p²=0.231）,hip flexion angle（p=0.003,η_p²=0.277）,knee flexion angle（p<0.001,η_p²=0.619）and the higher relative height of center of mass（p=0.043,η_p²=0.523）,and tended to landing by heels（p=0.029,η_p²=0.424）at the post-fatigue.（3）Compared with the single-leg drop jump,the side-cutting showed a smaller trunk tilt angle（p=0.008,η_p²=0.363）,relative height of center of mass（p<0.001,η_p²=0.953）and a larger angle of hip internal rotation（p=0.037,η_p²=0.259）,and tended to landing by heels（p<0.001,η_p²=0.68）.（4）Trunk tilt angle(F^[1,14]=8.43,p=0.012,η_p²=0.376),hip internal rotation(F^[1,14]=6.804,p=0.021,η_p²=0.327)and knee external rotation(F^[1,15]=12.146,p=0.003,η_p²=0.447)had significant interaction effect on fatigue and task at the maximum knee flexion.the side-cutting showed a smaller trunk tilt angle（p=0.032,d=0.44）at the post-test.Side-cutting showed larger angle of hip internal rotation（p=0.037,d=0.48 and p=0.001,d=0.96）and smaller external rotation Angle of the knee joint（p<0.001,d=0.93 and p<0.001,d=1.77）at the per-fatigue and post-fatigue than single-leg drop jump.（5）At the maximum knee flexion,compared with the single-leg drop jump,the side-cutting showed a smaller hip flexion angle（p=0.001,η_p²=0.556）and the knee flexion angle（p<0.001,η_p²=0.586）.（6）trunk(F^[1,15]=5.281,p=0.036,η_p²=0.194)and hip joint(F^[1,15]=4.782,p=0.045,η_p²=0.242)sagittal ROM had an interaction between fatigue and task.The single-leg drop jump showed a large sagittal ROM of the trunk（p=0.031,d=0.74）and hip（p=0.007,d=0.44）joint at the post-fatigue.（7）Compared with the per-fatigue,a large sagittal ROM of the knee join was showed for post-test（p<0.001,η_p²=0.631）.In addition,compared with the single-leg drop jump,the side-cutting showed a large sagittal ROM of the knee joint（p=0.016,η_p²=0.351）.Conclusions:Compared with the per-fatigue,Soccer players showed significant decrease for trunk tilt angle,hip flexion angle and knee flexion angle cause more upright landing posture,and kinematic characteristics such as prone to landing by heels and large sagittal ROM of the knee joint at the initial contact during single-leg drop jump and side-cutting,may increase the risk of ACL injury.In addition,side-cutting also show a large knee abduction angle at the post-fatigue.Trunk and lower extremity kinematics had no significant effect on fatigue and task at maximum knee flexion,may not have much impact on the ACL.Side-cutting may cause the ACL injury risk than single-leg drop jump at the post-fatigue during high-risk task.Suggest:The main training goal should be to increase the sagittal plane flexion angle,such as the trunk tilt angle,and to emphasize more flexion landing posture in future training.Strength or joint contraction training for related muscles such as the gluteus maximus,especially for side-cutting that require targeted training.