Effects of Fatigue Intervention on Biomechanics of Lower Extremity during a Stretch-Shortening Cycle Movement
Sun Xiaole;Xia Rui;Zhang Xini;Yang Yang;Fu Weijie;Shanghai University of Sport;
Objectives To explore the effect of fatigue intervention on biomechanics of lower extremi-ty and performance during the stretch-shortening cycle(SSC) movement-drop jumps(DJ). Methods The Vicon motion capture system and 3 D Kistler force plates were used to collect sagittal plane kine-matics and ground reaction force data synchronously of a total of fifteen trained male athletes underpre-and post-fatigue conditions with shuttle running + vertical jumping fatigue protocol. The joint an-gle,joint moment,power,work,and leg/joint stiffness were compared before and after fatigue. Results Af-ter fatigue,the maximum height of DJ decreased(P0.05),while the touchdown angle and the range ofmotion(Δθ) of knee and ankle joints,as well as the occurrence time for the eccentric,concentric andtotal phase increased(P0.05). However,the maximum push-off moment and power of knee reduced(P0.05). The stiffness of knee and ankle joints during the eccentric phase reduced,resulting in the reduc-tion of the leg stiffness(P0.05). Moreover,the energy absorption and net energy of the ankle joint de-creased; meanwhile,the energy contribution of the knee joint decreased during the eccentric phase of aDJ task. Conclusion Fatigue changes the movement pattern,decreasing the control ability of the lowerextremity especially in the knee and ankle joint,and results in decreased performance. Moreover,thedecrease of leg,ankle and knee stiffness and the corresponding energy can be used as sensitive index-es to evaluate the performance of drop jumps in a fatigued condition.