Effect Of Fatigue On The Biomechanics Of The Lower Limbs In Drop Jumping Movements At Different Heights

Purpose:According to the movement characteristics of drop jumping,the changes in mechanical parameters of drop jumping under different fatigue states and drop heights were compared,and the changes of biomechanical characteristics of the lower limbs under different fatigue states and drop heights were further investigated on the basis of the influence of individual factors,to further reveal the intrinsic connection between fatigue and exercise load and lower limb performance and injury in drop jumping training from the perspective of exercise biomechanics The mechanism of fatigue and exercise load in drop jump training was investigated.Methods:Twenty-one male undergraduates majoring in physical education at the School of Physical Education of Soochow University were selected to participate in this test,and fatigue was induced through the fatigue induction scheme of folding run+vertical jump.The Vicon infrared high-speed motion capture system and the 3D force measurement platform were used to collect the biomechanical parameters of the lower limbs of subjects who completed the drop jump at 40cm and 60cm drop heights with no fatigue(NF),moderate fatigue(MF)and severe fatigue(SF)simultaneously.Visual 3D software was used to process the data,and a two-factor repeated measures ANOVA was used to statistically analyze the examined parameters,and the significance level was set at 0.05.Results:(1)Fatigue level had a significant main effect on the kinematic and kinetic indexes of the drop jump action(P<0.05).In other words,compared with the NF state,the height of takeoff at MF and SF decreased significantly(P<0.05),the hip and knee flexion angles,the maximum hip and knee flexion angles,and the changes in hip,knee,and ankle angles at the moment of touchdown decreased significantly(P<0.05),and the peak angular velocity of hip and knee joints during the stirrup extension period also decreased significantly(P<0.05);at the SF state,the maximum ankle plantarflexion angle,the peak angular velocity of ankle joints during the stirrup extension period decreased significantly(P<0.05),The maximum ankle plantarflexion angle and the peak ankle angular velocity during the stirrup-extension period were reduced when the SF state was reached(P<0.05).RSR and RSI were also significantly reduced in MF and SF compared to NF(P<0.05),and RSI was significantly reduced in SF compared to MF(P<0.05).In terms of kinetics,the peak knee stirrup moment and centripetal power of hip,knee,and ankle joints were significantly reduced in MF and SF compared to NF(P<0.05);V-GRF2 and centrifugal power of ankle joints during stirrup and extension period were significantly reduced in SF(P<0.05).(2)The drop height had a significant main effect on the kinematic and kinetic indexes of the drop jump(P<0.05).The knee flexion angle,maximum hip and knee flexion,ankle plantarflexion angle,and the amount of change in hip,knee,and ankle joint angles were significantly increased(P<0.05),and the peak angular velocity of hip,knee,and ankle joints were significantly increased(P<0.05),while RSI and RSR were significantly decreased during the cushion period compared with 40 cm touchdown(P<0.05).In terms of kinetics,compared with the drop height of 40 cm,the V-GRF1 and LR during the cushioning period from 60 cm height increased significantly(P<0.05),and the peak hip cushioning moment,hip and knee stiffness,lower limb stiffness and centrifugal power of hip,knee,and ankle during the cushioning period increased significantly(P<0.05);the knee and ankle stiffness during the stirrup extension period decreased significantly(P<0.05).(3)Different fatigue levels and drop heights had interactive effects on buffer time,peak ankle angular velocity during the buffering period,peak knee buffering moment,and peak ankle stirrup moment(P<0.05),as follows:compared with the drop height of 40 cm,the buffering time and peak ankle angular velocity during the buffering period increased significantly in the NF state compared with the drop height of 60 cm(P<0.05);in the MF state,the buffering time and peak ankle angular velocity during the buffering period increased significantly(P<0.05);in the MF state,the peak angular velocity of the ankle joint and the peak cushioning moment of the knee joint during the cushioning period were significantly increased(P<0.05),while the peak moment of the ankle joint stirrup and extension was significantly decreased(P<0.05);in the SF state,the peak cushioning moment of the knee joint was also significantly increased(P<0.05).From 40 cm height,the ankle extension moment in the SF condition was reduced compared with that in the MF condition(P<0.05).From a height of 60 cm,the ankle extension moment decreased in both MF and SF compared to NF(P<0.05),and the peak angular velocity of the ankle joint during the cushioning period was also significantly reduced in SF(P<0.05).Conclusions:(1)Deepening fatigue and increasing drop height both altered the lower extremity kinematic and kinetic loading patterns of the drop jump.(2)From MF to SF state,the lower extremity stiffness of drop jumping action further deepened,the pedal extension strength decreased,and the risk of lower extremity injury increased.(3)Since the higher height of descent,the lower extremity adopts a greater flexion angle to cushion the ground reaction force,which may affect the subsequent stirrups and extension tasks,while somewhat increasing the lower extremity joint load.(4)The combined effect of drop height and fatigue may affect the jumping technique to varying degrees,and as fatigue deepens,dropping from a higher height may further increase the load on the lower extremity,reducing athletic performance and increasing the risk of injury.