Effect Of Anticipation On Lower Extremity Kinematics And Kinetics For Basketball Collegiate Students During Stop Jump Shooting

Purpose:The stop jump shooting is not only the most commonly used means of scoring in basketball games,but also a high-risk action that causes patella tendinopathy in basketball players.Especially in fierce competition,athletes need to react quickly according to the defensive actions of the defender,and the defensive actions are often uncertain and unanticipated.Most of the previous studies focus on the analysis of the sport biomechanical characteristics of the athlete’s stop jump shooting in the anticipated states,which did not fully understand the real situation of the athlete in the actual game.The study attempted to simulate the different anticipated states in the real game environment,and to explore the impact of the anticipated states on the sport biomechanics of the lower limbs of collegiate basketball players in the process of completing the stop jump shooting,so as to obtain comprehensive evaluation of the patella caused by the stop jump shooting.The injury risk of tendinopathy was expected to provide a basis for athletes in the formulation of sports training and injury prevention programs.Methods:In this study,20 male college basketball players were recruited to carry out the experimental research on the anticipated states.The infrared light point three-dimensional motion capture system（Nokov）was used to collect the kinematic data of the athletes when they completed the step stop jump shot and jump stop jump shot under anticipated and unanticipated states,and the dynamic data was collected by the Bertec force plates.The kinematics and dynamics data of stride jump shooting and jump stop shooting in different anticipated states were obtained by sampling frequency of 200Hz and 1000Hz respectively.After the data collection is completed,it was imported into Cortex-642.6.2 software for identification processing,the joint motion Angle and take-off height of human lower limbs were calculated.Three-dimensional human torques,vertical ground reaction forces and loading rates of knee-extending torques were calculated by inverse dynamics method,and the joint torques were normalized as multiples of the product of height and body weight.The effects of different anticipated states and movements on the kinematics and dynamics of the lower limb were determined by 2×2 repeated measurement two-factor ANOVA.If there was any interaction,the differences between anticipated and un anticipated states and stride and jump stop shooting movements were compared by paired sample T-test.The significance criterion was defined as a first class error probability of no more than 0.05.Results:（1）There was a significant interaction between the anticipated states and the hip flexion angle of different stop jump shooting movements(F_[1,38]=4.825,p=0.012)at the initial contact.The jump stop shooting showed a larger hip flexion angle than the stride stop shooting in both anticipated and unanticipated states（p<0.001,p<0.001）.There was a significant interaction between the hip adduction and abduction angle between the anticipated states and stop jump shooting movements(F_[1,38]=4.326,p=0.042).In both anticipated and unanticipated states,the stride stop shooting showed a larger hip abduction angle than the jump stop shooting（p<0.001,p=0.002）.The hip abduction angle was larger in the anticipated states than in the unanticipated states（p=0.031）.There was a significant interaction between the knee flexion angle of the anticipated states and different stop jump shooting movements(F_[1,38]=6.221,p=0.012).In both anticipated and unanticipated states,the jump stop shooting showed a larger knee flexion angle than he stride stop shooting（p<0.001,p<0.001）.Both the stride stop shooting and the jump stop shooting showed greater knee flexion angle than anticipated states（p=0.006,p<0.001）.There was a significant interaction between the hip flexion moment of the anticipated states and the different stop jump shooting movements(F_[1,38]=3.112,p=0.024).In the unanticipated states,the stride stop shooting showed a greater hip flexion moment than the jump stop shooting（p=0.016）.（2）There was a significant interaction between the hip adduction and abduction angles between the anticipated states and the different stop jump shooting movements(F_[1,38]=5.437,p=0.031)at the peak of the ground reaction force,In both anticipated and unanticipated states,the stride stop shooting showed a larger hip abduction angle than the jump stop shooting（p<0.001,p<0.001）;There was a significant interaction between the anticipated states and the ankle dorsal extension plantar flexion angle of different stop jump shooting movements(F_[1,38]=5.811,p=0.014).In both anticipated and unanticipated states,the stride stop shooting showed a larger dorsal extension angle than the jump stop shooting（p<0.001,p<0.001）.Compared with the anticipated states,the stride stop shooting and the jump stop shooting showed larger dorsal extension angle（p<0.001,p<0.001）.There was a significant interaction between knee flexion and extension moments of different stop jump shooting movements in the anticipated states(F_[1,38]=4.385,p=0.027).In the anticipated states,the jump stop shooting showed a greater flexion moment than the stride stop shooting（p<0.001）.The stride stop shooting a greater flexion moment（p=0.039）in the unanticipated states,and the jump stop shooting showed a greater flexion moment（p=0.049）in the anticipated states.（3）Regardless of anticipated states,the stride stop shooting showed greater knee flexion moment than the jump stop shooting（p=0.047）at the initial contact,Regardless of the anticipated states,the stride stop shooting showed a larger hip external rotation angle（p=0.036）.Regardless of the stop jump shooting movement,the anticipated states showed a larger ankle dorsal extension angle（p<0.001）.（4）Regardless of the anticipated states,the stride stop shooting showed greater dorsal extension moment than the jump stop shooting（p=0.043）at the peak of ground reaction force,Regardless of the stop jump shooting movement,the anticipated states showed a larger external rotation angle of the hip（p<0.001）.Conclusion:（1）The risk of injury is greater in stride stop shooting than in jump stop shooting.The stride stop shooting landed in a more upright way,increasing the load on the lower limb joints and increasing the impact force on the lower limb joints.And the stride stop shooting also shows a smaller dorsal extension angle when landing,which limits the dorsal extension of the ankle while following the ground with the foot,thus reducing the ankle’s cushioning ability.In addition,the large internal rotation angle of the hip joint during the stride stop shooting will aggravate the lateral tension of the quadriceps femoris on the patella,leading to the dislocation of the extensor mechanism and resulting in patellar tendon injury.（2）The risk of injury is greater in unanticipated states than in anticipated states.unanticipated states landing speeds up the conversion of knee flexor net torque to knee extensor net torque,which makes the knee extensor mechanism suffer high impact force.In addition,the unanticipated states also showed a smaller dorsiflexion angle of the ankle,which placed a greater load on the lower limb joints.（3）The landing buffer stage shows a greater rate of change of knee joint moments than the stop jump shooting buffer stage,which will reduce the stability of the knee joint.In addition,the unanticipated states of the stop jump shooting showed a higher take-off height than the anticipated states,which made the lower limb joints need to disperse greater ground reaction force,which would increase the occurrence of patellar tendon injury.Suggestions:（1）More attention should be paid to the landing way of the jump shot,in the training,we should try to actively increase the forward leaning degree of the whole trunk and the flexion angle of the knee joint,and try to avoid the jump shot with the heel.In addition,during the training warm-up,we can focus on stretching the calf to improve the dorsal extension range of the ankle joint,and pay attention to the strength training of the calf plantar flexor muscle group.（2）More training could be carried out to simulate the Unanticipated states in the daily training,such as setting random obstacles or using the grating system similar to this experiment.（3）In the unexpected state training,the quadriceps and gluteus maximus muscle groups can be trained specifically to improve the control of the stability of the lower limb joints such as patella and enhance the coordination ability of the lower limb in the unexpected state.