Biomechanical Characteristics Of The Lower Limbs In Drop Jump Movements At Different Heights And Distances

Objective: Drop jump is a popular method for improving jumping ability and rapid lower limb strength training.This training involves jumping from an elevated platform to the ground and immediately rebounding upward.By measuring the mechanical characteristics of the joints,muscles,and ligaments of the lower limbs across different heights and distances,this study aims to analyze the influence of height and distance on the biomechanical characteristics of deep jumps,and provide theoretical references for lower limb muscle strength training.Method: In this study,musculoskeletal modeling using Open Sim simulation software was employed to investigate the biomechanical characteristics of the lower limbs.The study involved 20 male participants with varying heights and distances of drop jump,and data were collected using 8 Qualisys 600+ high-speed cameras,an AMTI 3D ergometer and 16 channels of DELSYS surface EMG synchronized with the Qualisys Track Manager motion capture system.Kinetic and surface EMG data were collected and muscle mechanics parameters were obtained using Open Sim musculoskeletal simulation software.Data were then statistically analyzed using MATLAB and SPSS statistical software.Results: 1.Kinematic characteristics: The landing height and distance exhibit a significant effect on the hip,knee,and ankle joints.Specifically,at the hip joint,the abduction angle increases significantly with increased height and distance;at the knee joint,the flexion angle during the cushion phase increases with increased height,but distance has no significant effect;at the ankle joint,the plantar flexion angle increases significantly with increased height and distance.2.Kinetic characteristics: With respect to the hip joint,increased distance significantly reduces the hip extension moment and minimizes the load on hip extension.For the knee joint,an increase in height and distance significantly elevates the knee extension moment during the pre-activation phase and leads to a rise in the internal retraction and internal rotation moment during the cushion and stirrup extension phases.As for the ankle joint,an increase in height and distance significantly reduces the ankle plantar flexion moment.Moreover,an increase in height significantly amplifies vertical ground reaction forces,whereas an increase in distance results in reduced vertical ground reaction forces.3.Muscle mechanics: The gluteus maximus,gluteus medius,and gluteus minimus control the external rotation and abduction of the hip joint respectively.At the knee joint,the quadriceps,hamstrings,and anterior cruciate ligament help maintain the stability of the knee.Increasing the height and spacing of the deep jump enhances the pre-activation phase of the biceps femoris,leading to a significant increase in muscle strength.The hallux valgus muscle at the ankle joint controls ankle plantar flexion and mild inversion under the talus,and experiences the highest stress throughout the movement.Conclusions: 1.Increasing the height and spacing of the deep jump had a lesser effect on the hip joint.Increasing hip flexion and internal rotation helps to lower the body’s center of gravity and cushion the joint.2.Increasing the height and spacing of the jump affects the kinematic and kinetic characteristics of the knee joint,which in turn impacts the performance of the quadriceps and hamstrings,and has an effect on the "lengthening-shortening contraction cycle".3.The ankle joint plays an important supporting role,with the calf flounder muscle being the most heavily loaded throughout the movement.4.Selecting the appropriate height and spacing of the landing during exercise training could be an adjustment strategy to reduce joint loading while increasing the rapid strength of the lower limb muscles.