Biomechanical Analysis Of Lower Limbs Under Different Variations Of Functional Movement Screening ——An Example Of The Deep Overhead Squat Test

The deep overhead squat test（DST）is one of the main tests of functional movement screen（FMS）.A large number of studies have shown that functional action screening has been widely used in the field of sports,occupies an important position in the field of sports injury risk assessment,and the score of the deep overhead squat test is highly correlated with the total score of FMS,and when the test conditions are limited,the over-top squat test results can be used to replace the entire test results,but few studies have paid attention to the change of foot position in the deep overhead squat action and the biomechanics of limbs in different foot position modes.It is necessary to clarify the deep causes of the requirement to tiptoe forward in the deep overhead squat action test and the biomechanical changes in the lower extremities in different foot position modes.In this study,12 healthy male fitness and bodybuilding enthusiasts were recruited to perform deep overhead squats with extrafoot rotation 0°,extrafoot rotation 30°,and extrafoot rotation 60°.The Vicon acquisition system and the Kistler 3D force tester acquire the subject’s lower limb kinematics data and ground reaction force data.The Noraxon Surface ELECTROMET System collects muscle EMG signals from the lower extremities.Inverse dynamics calculations were performed by Visual3 D inverse dynamics,calculating the differences in biomechanics of the trunk and lower limbs under three different over-the-top squats.Differences in MYO data under three deep overhead squats were analyzed by Noraxon Surface EMG Analysis Software.The study found that（1）the change of foot angle has a greater impact on the maximum value of hip abduction and adduction,the larger the angle of the foot position,the greater the abduction angle of the hip joint;the greater the impact on the abduction of the knee joint,and the abduction angle of the knee joint also increases when the foot angle increases;the impact on the knee joint is also concentrated on the Y axis,and the movement mode of the ankle joint on the coronal surface is abduction-adduction-lowest point of action-abduction-adduction,the greater the foot angle,the greater the abduction angle of the ankle joint.（2）In the process of deep overhead squat action,the COP offset area is the smallest（231.78±47.85）under the 30° foot position,and there is a significant difference with the COP offset area under the 0 ° and 60° foot positions,and it can be concluded that the stability of the deep overhead squat is the best at 30 ° foot position,and the action stability is poor at 0 ° and 60 ° angle.（3）From the surface emeryoelectric characteristics of the squat stage of the deep overhead squat,the gluteus major muscle,the middle gluteus muscle and the biceps femoris muscle have the smallest degree of discharge and activation under the 0 ° foot position,and the maximum degree of muscle discharge and activation under the 60 ° foot position;the erector spinal muscle,the semi-tendon muscle and the tibiaterior muscle have the greatest degree of discharge and activation under the 0 ° foot position,and the minimum degree of activation under the 60 ° foot position.The maximum muscle discharge,activation and contribution rate of the tibia anterior muscles in the squat stage are the main working muscles of the process,and the muscle discharge,activation degree and maximum amplitude of the tibial anterior muscles under the 0° foot position are greater than 30° and 60° foot positions.The muscle contribution rate of each muscle in the squat stage is the largest muscle contribution rate of the tibial front muscle,followed by the anterior thigh muscle group and the vertical spinal muscle.（4）The surface emery characteristics of the squat stage can be obtained from the surface emery of the squat stage,the muscle discharge,activation degree and muscle contribution rate of the anterior thigh muscle group are the largest,followed by the vertical spinal muscle,followed by the tibia anterior muscle,which can be seen that the main force muscle group in the squat stage is mainly the anterior thigh muscle group,followed by the vertical spinal muscle and the tibia front muscle.Gluteus major muscles,biceps femoris,and gastrocnemius muscles have the least degree of discharge and activation at 0° foot position and the greatest at 60° foot position.The erector spinal muscles,the hemitemis muscles,and the right tibia front muscles have the greatest degree of discharge and activation at 0° foot position and the least at 60° foot position.（5）When screening for deep overhead squat movements,when the foot position is at 0 °,the abduction angle of the hip knee and ankle joint of the lower limb is the smallest,the center of the plantar pressure is offset greatly,the participation of the vertical spinal muscle and the tibia front muscle is higher,and the difficulty of the action can expose more functional problems.