A Comparative Study Of Lower Extremity Biomechanics In Male And Female Athletes Between Countermovement Jump And Controlled Drop Jump

PurposeIn competitive sports,ACL injuries commonly occurred during jump landing tasks with a non-contact mechanism.At present,researchers mainly mimiced the actions that prone to ACL injury in the laboratory,such as drop landing(DL)or drop jump(DJ),and collected relevant lower extremity biomechanics to analyze and explore potential biomechanical factors that may lead to ACL injury.However,in recent years,some studies had questioned the validity of the laboratory testing tasks in revealing the mechanisms that may lead to ACL injury during the landing phase,and previous studies had also observed differences in landing biomechanics between the fixed height laboratory landing tasks and the actual jump landing tasks.Counter movement jump(CMJ),as a common jumping landing movement in real-life sports,was not often seen in landing tests,and no studies had directly compared the lower extremity mechanics between CMJ and fixed-height DJ tasks.Therefore,the purpose of the present study was twofold: 1)to compare lower extremity landing biomechanics between CMJ and DJ(including the first landing and the second landing)to explore whether CMJ can be used as ACL injury risk assessment task to represent landing mechanics of actual jump landing tasks;2)to identify whether landing mechanics will show differences between male and female,in order to better guide sports training and formulate injury prevention training programs.Methods39 healthy recreational college athletes were recruited.Each participant performed two jump landing tasks: CMJ task and 30 cm DJ task.The Vicon 3D motion capture system and 3D Kistler force plates were used to record kinematic data and force data for each trial,synchronously.A two-way ANOVA with repeated measures was used to determine main effects and interaction effects between jumping type(CMJ vs DJ＿L1 vs DJ＿L2)and sex(male vs female)for kinematic and kinetic variables during landing phase.All data was performed in SPSS 22.0,significant levelα was set at 0.05.Results1)The plantarflexion angle at initial contact,knee flexion angle at initial contact and maximum dorsiflexion angle showed significant interaction effects between landing type and sex.In male,CMJ and the second landing of DJ indicated significantly smaller knee flexion angle at initial contact,larger plantarflexion angle at initial contact and maximum dorsiflexion angle;However,in female,only CMJ showed significantly smaller knee flexion angle at initial contact,larger plantarflexion angle at initial contact and maximum dorsiflexion angle,no differences were observed in the first and second landing of DJ;2)In landing phase,the kinematics of hip and knee joints displayed significantly jumping type main effects.The first landing of DJ showed greater hip flexion angle at initial contact,knee flexion angle at initial contact,maximum hip flexion angle,maximum knee flexion angle and ROM of hip and knee joints;CMJ and the second landing of DJ showed similar results;3)Only ankle kinematics showed gender main effects: female indicated significantly greater ankle flexion angle;Meanwhile,compared with the male,the female showed significantly greater ankle abduction angle during the landing phase;4)The peak extension moment of hip,knee and ankle joints in sagittal plane displayed significant interaction effects.In male,the first landing of DJ showed significantly smaller peak extension moment of hip,knee and ankle joints;However,in female,the first landing of DJ only showed significantly smaller peak ankle extension moment.In these three landing tasks,male showed significantly greater peak extension moment of hip,knee and ankle joints than female;5)The peak v GRF showed significant interaction effects.In male,the peak v GRF showed differences among these three landing tasks;In female,there was no differences among these three landing tasks.In CMJ and the second landing of DJ,male showed greater peak v GRF than female,but there was no gender differences of the peak v GRF in the first landing of DJ.The first landing of DJ also showed greater loading rate and shorter impact loading time than CMJ and the second landing of DJ.Conclusions1)There were significant differences in lower extremity biomechanics between landing followed jumping from the ground(CMJ and the second landing of DJ)and landing from a fixed height platform(the first landing of DJ).It suggested that the landing test from a controlled height platform may deviate from the real sports situation,and we should take with caution when evaluating the risk of knee injury using this landing task;2)There were significant differences in lower extremity biomechanics among these three landing tasks between male and female.Compared with male,female indicated greater ankle flexion angle,ankle abduction angle and ankle flexion ROM.However,the sagittal kinematics of hip and knee joints didn’t show gender differences.This ankle dominant strategy and increased ankle abduction angle may increase the landing instability of female,which may raise the risk of injury in women.