Lower Extremity Biomechanical Analysis Of Squat Pulsing With Different Weights

Research objective: Squat jump training with heavy weight,as a kind of training with heavy weight over equal length,has the advantage of resistance training with heavy weight to improve the maximum strength,and has the advantage of over equal length training to improve movement speed and explosive power.Previous studies on load-bearing squat jumps mostly focused on whether load-bearing squat jumps can improve the explosive power of lower limbs,or explored the optimal power load under different loads based on RM loadbearing standards.Previous relevant studies have shown that more appropriate weight load can improve the effect of lower limb explosive power training,and the training effect of overlength weight training is better under the weight of 30%1RM squat weight and 30%MVC(maximum isometric strength of lower limb).However,for ordinary fitness enthusiasts or those with low training level,in terms of weight selection,carrying out weight over-length training with 10%MVC weight has better training effect.Compared with other weights,10%MVC weight can exert greater explosive power,and 30%1RM squat weight of ordinary fitness crowd can hardly exceed their own weight.Taking the zero to dead weight range as the weight standard,there are few studies on the influence of lower extremity biomechanics on squat and jump with weight.In this study,the basic biomechanical characteristics of the three joints of lower limbs,hip,knee and ankle during the period from upright to airborne squat jump with load were analyzed,and more scientific guidance and suggestions were given for squat jump training with load based on dynamic and kinematic data changes.Research methods: This study was completed in the Efficacy Laboratory of the Key Laboratory of Sports Engineering of the State General Administration of Sport [funded by the Key Laboratory of Sports Engineering of the State General Administration of Sport].18 males from Wuhan University of Sport were selected as subjects,all of whom had certain fitness foundation and training experience.Each subject completed the weight-bearing squat and jump exercise test with increasing weight in the range from zero to self-weight.The author used Vicon(250Hz)infrared motion capture system and Kistler(1000Hz)threedimensional dynamometer system to collect the original kinematics/dynamics data of the three joints of lower limbs(hip,knee and ankle)synchronously.Ten subjects with valid experimental data were selected for analysis,and the original kinematics/dynamics data were analyzed and processed by Visual3 D signal analysis software,and then the experimental data were exported in Print ASCII format for further analysis in Excel2021.SPSS22.0 statistical software was used to process the data,and the homogeneity test of variance was conducted.one-way ANOVA was used for multi-group analysis,and differences between groups were analyzed by Post-hoc test,with the significance level set as P < 0.05.Research results:(1)Different weight bearing has an effect on joint Angle: With the increase of weight bearing,the angles of knee,hip and ankle joints of all subjects changed,and the changes of flexion angles of hip and knee joints showed a downward trend,while the ankle joint Angle fluctuated up and down,and was least affected by the changes of weight bearing.The maximum and minimum ankle Angle MAX values were 104.3±2.63° and 101.2±1.87°.(2)Different weight loads have an impact on the joint angular velocity: Under increasing weight loads,the angular velocity of the knee,hip and ankle of all subjects showed a downward trend.MAX value of ankle joint angular velocity was the largest,followed by that of knee joint,and that of hip joint was the smallest.(3)Different weight loads have an impact on joint forces: Under increasing weight loads,the joint forces of knee,hip and ankle of all subjects show an increasing trend.Under increasing weight load,the joint force MAX value of hip joint was the largest,followed by that of knee joint,and that of ankle joint was the smallest.(4)Different weight loads have an impact on joint power: Under increasing weight loads,the power output of knee,hip and ankle joints of all subjects increased first and then decreased.The knee joint has the highest power output at 65 KG weight,the ankle joint has the highest power output at 55 KG weight and the hip joint at 35 KG weight.The hip joint had the highest power output,followed by the knee joint,and the ankle joint had the lowest power output.Combined with the characteristics of Angle change,the lower limb output power was the highest in the hip joint followed by the knee joint.The hip and knee joint had a higher power output interval with an intermediate weight value of 50 KG,and it was found that the knee Angle was less than 100 degrees after 50 kg.(5)Different weights have an effect on the knee torque: Under increasing weight,the knee torque of all subjects has an upward trend.It can be observed that the maximum joint torque of the knee joint is 2.17±0.13Nm/kg when the load is 85 KG,and the maximum joint torque of the knee joint occurs when the Angle of the knee joint is maximum.Research conclusion:(1)Weight-bearing squat jump,as a load-bearing super-equal length contraction action,can effectively improve the explosive power of lower limbs.With the increase of weight,the angular velocity of the three joints of lower limbs decreases correspondingly,and the lower limb base strength does not directly affect the change trend of angular velocity,so it cannot directly affect the motion speed.To improve the corresponding joint speed,it is not only necessary to improve the strength of lower limbs;(2)Weight-bearing squat jump in increasing weight,joint force changes accordingly,and the joint force of the hip output is greater than the joint force of the knee and ankle joint,so improve the lower limb joint force can be more focused on improving the hip joint force training,such as strengthening the waist hip and other muscle strength;(3)The three joints of the hip,knee and ankle of the common male youth have their own optimal power load within the range of zero to dead weight.Ordinary young men can choose about 35 KG weight for training when improving the explosive power of the hip joint,about65 KG weight for training when improving the explosive power of the knee joint,about 55 KG weight for training when improving the explosive power of the ankle joint;(4)Common male youth weight-bearing squat jump lower limb hip knee ankle three joints in the range of zero to dead weight,has the best power load.In order to improve the lower extremity explosive power and the selection of weight standards,ordinary young men can focus on the weight squat jump in the range of zero to dead weight,can choose about50 KG weight for training,has a high power output;(5)Weight-bearing squat jump lower limb training in the range of zero to self-weight,squat Angle should not be too large,do not need to squat to the thigh parallel to the ground,knee Angle can be about 95 degrees.And squatting too low can increase the risk of knee injury.Pay more attention to the maximum knee Angle MAX during training,when the risk of knee injury is greatest.In addition,the MAX value of ankle joint Angle should be about103°.Stable ankle joint Angle is conducive to the stability of weight-bearing squat jumping and reduce the risk of injury.