Effects Of Footwear And Fatigue On Lower Extremity Biomechanics During Impact-related Drop Landings

IntroductionDuring running and landing,injuries may theoretically be induced by repetitive impact forces loaded on human lower extremities.Modern sports shoes play a role of cushioning and reducing impact forces loaded on human lower extremities and feet during running and landing,based on its structure and material.However,because the human body has a certain ability to adapt and adjust,so that the cushioning effect of sports shoes has not only limited to a purely mechanical effect.Besides,long time and high intensity exercise always lead to fatigue,and neuromuscular fatigue will lead to changes in skeletal muscle control.So,the function of cushioning of the sports shoes would be more significant? Therefore,the purpose of this study is to examine the effect of the cushioning / non-cushioning shoes on impact characteristics,kinematics and dynamics of the lower limbs under fatigue conditions during drop landing movement.MethodsFifteen male basketball players(22.1 ± 1.7 years old,179.3 ± 3.2 m,72.2 ±5.5Kg,)from Shanghai University of sports were selected as subjects.They were performed sports intervention which including 15×4 m reentry run and 5 consecutive counter movement jump for a group,they would repeat overall movement until their jumping heights were less than their 70% maximum heights.Ten 3D infrared high-speed cameras(Vicon,240Hz)and two force plates(Kistler,1200Hz)were used to collect the ground reaction force,kinematics and dynamics parameters of the subjects with different cushioning shoes when they were falling from 60 cm height.Two way repeated measures-ANOVA were used to determine the effects of fatigue on these variables.The significance level α was set at 0.05.Results1)The effect of different shoes on sagittal joint kinematics of the hip,knee and ankle before and after fatigueThere was no significant difference in maximum angle,minimum angle and the arrival time of hip,knee and ankle,as well as the range of motion of three joints in different shoes pre-and post-fatigue.As for maximum angular velocity,only the hip joint angular velocity was greater in high cushioning shoe than that of control shoe in pre-fatigue.2)The effect of different shoes on sagittal joint kinetics of ankle before and after fatigueFor the plantar flexion peak moment and joint stiffness of ankle,we found there were no significant changes both in moment,joint stiffness and arrival time of ankle wearing different shoes no matter pre or post fatigue.3)The effect of different shoes on the vertical impact force loaded on lower extremities before and after fatigueThe peak impact force,loading rate at heel and loading rate at forefoot in high-cushioning shoe were significant lower than that of control group after fatigue(p<0.01).Meanwhile the time to peak impact force of fore foot was more longer than CS after fatigue(p<0.05).In addition,the loading rate was significant lower in high-cushioning shoe at heel pre-fatigue(p<0.01).ConclusionsWe found that the protective effect of high-cushioning shoe was not very significant before neuromuscular fatigue;but especially when the human neuromuscular control strategy was not work well during landing after fatigue,even though there was no significant difference in lower extremities biomechanics(e.g.kinematics and kinetics)in this study,wearing high-cushioning shoes can significant reducing the impact and loading rate at forefoot and heel.According to these results,sports shoes can provide cushioning protection before fatigue;wearing high-cushioning shoes can provide greater protection for the body during movement post fatigue,thereby reducing the risk of injury.