Effects Of Different Step-lengths On Biomechanical Characteristics Of Lower Limbs During Forward Lunge Squatting

Purposes: The purpose of this study is to determine the effect of step size on the biomechanics of lower limbs in lunge movements.For the four kinds of asynchronous distance(50%,70%,100%,120% leg length),the effects on the biomechanical characteristics of the lower limbs were analyzed,including: lower limb hip joint,knee joint,ankle joint flexion angle,flexion and extension moment,each m;uscle activation and knee patellofemoral joint stress.Determine the optimal step distance for different training purposes,and provide a theoretical basis for sports training and rehabilitation training.Methods: This study screened 20 students of Beijing University of Physical Education(average age of 23.9±3.7,average height of 175.1±4.9),based on the leg length of the subjects(50%,70%,100% of the leg length respectively)and the weight of the 10 RM barbell is used as the load.Using the 8-camera infrared high-speed motion capture system,the wireless electromyography tester and the force measuring platform to collect the kinematic and kinetic data during the lunge movements.The single-factor repeated measures analysis of variance was used to test the difference between the peak hip joint,the knee joint,the ankle joint flexion and extension angle,the peak moment and the peak tibiofemoral joint stress under the unsynchronized distance;the two-factor repeated measures analysis of variance was used to verify the unsynchronized distance.The difference between the degree of activation of lower limb muscles in the descending phase and the ascending phase.Results: The maximum hip flexion angle at 120% step is greater than 100% step,100% step is greater than 70% step;the maximum knee flexion angle at 120% step is greater than 70%,50% step,the 100% step is greater than 70% and 50% step;the maximum ankle flexion angle at 120% step is greater than 100%,70%,50% step,100% step is greater than 70%,50 steps.Maximum hip joint extension moment at120% step is greater than 100%,70%,50% step,100% step is greater than 50% step,70% is greater than 50% step;maximum knee extension moment at 120% step is greater than 100%,70%,50% step,100% step greater than 70%,50% step,70% step greater than 50% step.The peak patellofemoral joint stress at 120% step is less than100%,70%,50% step.The Gluteus Maximus muscle RMS of 50% step is less than70%,100%,120% step,70% step is less than 120% step;Gluteus Maximal RMS is less than the ascending phase in the lunge declining phase.The Medial Vastus muscle RMS of 50% step is less than 100%,120% step,The Medial Vastus muscle is less than the ascending phase in the lunge declining phase.There was no significant difference in The vastus lateralis muscle RMS under the unsynchronized distance,and there was no significant difference in the descending and declining phase of the lunge.The rectus femoris muscle RMS of 50% step is less than 70% and there was no significant difference in the descending and declining phase of the lunge;The biceps femoris muscle RMS of 50% step is less than 70%,100%,120% step,70% step is less than 120% step;biceps femoris RMS is less than the ascending phase in the lunge declining phase.The Semitendinosus muscle RMS of 50% step is less than70%,100%,120% step,70% step is less than 120% step,100% step is less than120% step;Semitendinosus RMS is less than the ascending phase in the lunge declining phase.The RMS of the medial of the gastrocnemius is less than 100% and120% step at 50% step,and the 70% step was less than 100% and 120%.There was no significant difference in the RMS of the medial of the gastrocnemius during the descending phase and the ascending phase.The lateral head of the gastrocnemius is less than 100% and 120% step at 50% step,and the step of 70% is less than 100% and120% step.Conclusions: 1.The peak extending moment of the hip joint gradually increases with the increase of the step size;the peak bending moment of the knee joint is smaller under the larger step,and the knee flexion angle at the moment of the peak extension moment is more Small,it is recommended that patients with hip injury use a small step in the rehabilitation of the lungs,knee joint injury or limited range of motion for patients with a larger step for training.2,The larger step training for the lower extremity gluteus maximus,biceps femoris,semitendinosus,medial femoral muscle,rectus femoris and gastrocnemius muscle activation is higher,when the lunge action was applied to exercise training,the hip muscles,the biceps femoris,the semitendinosus,the medial femoral muscle,the rectus femoris and the gastrocnemius are the main training targets,and considering the optimal torque and muscle activation,100% step is the best for training.