Effects of Exercise-Induced Fatigue on Joint Mechanics,Stiffness,and Energy Absorption in Lower Extremity during Landings

Objective:To investigate the effects of two exercise-induced fatigue protocols, namely, constant speed running (running) and shuttle running+maximal vertical jumping (running+jumping) fatigue protocols separately on sagittal joint mechanics, stiffness, and energy absorption of lower extremity during landing activities. Methods: Fifteen trained male athletes were required to execute five successful trials of drop landings from a 60-cm platform within the above-mentioned two fatigue protocols. The variables included v GRF, range of motion, joint mechanics, stiffness, and energy absorption in the sagittal plane movement. Results: Induced fatigue can increase COG displacement and each joint range of motion during landings (P< 0.05) . Post-tests using running + jumping fatigue protocol showed a significant increase in the MK1 (P<0.05) and a significant decrease in the vertical stiffness (P< 0.05) compared to pre-tests. The greater eccentric work was observed at hip joint (P< 0.05) within the running fatigue protocol, which correspondingly decreased the eccentric work at ankle joint (P< 0.01) . Conclusion:The control strategies of human lower extremity in post-fatigue were different compared with pre-fatigue. Additionally, due to different fatigue protocols, the control strategies of lower limbs were different in terms of kinetics, stiffness, and energy absorption of joints during landing activities. Kinematics and joint powers were mainly reflected in running protocol; while altered joint moments and stiffness were shown primarily in running + jumping protocol. Thus, there is a considerable biomechanical change in motor control of lower extremity during landings due to various exercise-induced fatigue protocols applied in human movement.