The Biomechanical Characteristics During Landing In Individuals With Unilateral FunctionalAnkle Instability

Purposes：The single-foot landing and the double-foot landing were tested inindividuals with and without unilateral functional ankle instability. The objective was toexplore the biomechanical characters of two different landing styles in individuals withunilateral functional ankle instability, the difference between the ipsilateral-foot landingand the contralateral-foot landing, and the difference between the single-foot landingand the double-foot landing in the ipsilateral with unilateral functional ankle instability.The theoretical and experimental basis was provided for the ankle injury prevention.Methods： Twenty male subjects with unilateral functional ankle instability(experimental group), according to the age, height, weight, training programs of lowerlimb morphology characteristic matching20male healthy subjects without functionalankle instability(control group). Single left-foot landing, single right-foot landing anddouble-feet landing, from40cm-high platform without initial speed, were tested byVicon-MX with infrared motion capture system and Kistler force platform.Thebiomechanical indexes, such as different directions of peak ground reaction force andcorresponds to the time、instantaneous degree of the knee and ankle joints within100msbefore and after landing、the maximum degrees and the corresponding time of kneeflexion and ankle extension after landing.Results：①During the ipsilateral-foot landing, there were significant differencesbetween both groups in the time to peak ground reaction force in anterior、medial andlateral directions, the maximum degrees of knee flexion and ankle extension andcorresponds to the time, instantaneous degree of the knee and ankle joints within100msbefore and after landing (P<0.05).②During the single-foot landing, there weresignificant differences between ipsilateral-foot landing and the contralateral-footlanding in the time to peak medial and lateral ground reaction forces, instantaneousdegree of the knee and ankle joints in100ms before and after landing, time to stabilization, the maximum degrees of knee flexion and the degree of ankle(P<0.05).③For the ipsilateral side of double-foot landing, there were significantdifferences between both groups on the vertical and lateral relative peak ground reactionforce and corresponds to the time, the medial direction of relative peak ground reactionforce and the timing of peak ground reaction force in anterior direction, instantaneousdegree of the knee and ankle joints in100ms before landing and other biomechanicalindexes(P<0.05). For the contralateral-side of double-foot landing, there weresignificant differences between both groups on the vertical and anterior relative peakground reaction force, the lateral relative peak ground reaction force, and time to peakground reaction force, instantaneous degree of the knee and ankle joints after landing,the time to maximum degrees of ankle extension and other biomechanicalindexes(P<0.05).④For the ipsilateral side of experimental group during theipsilateral-foot landing and the double-foot landing, there were significant differencesbetween two landing style on the vertical、anterior、posterior and lateral relative peakground reaction force, time to peak ground reaction force in all directions, the maximumdegrees of knee flexion and ankle extension, the maximum degrees of ankle jointinversion and time to the maximum degrees(P<0.05).Conclusions：①During the single-foot landing, there are no significantdifferences in individuals with and without unilateral FAI on each direction peak GRFafter landing, and there are no significant differences between the contralateral footlanding of unilateral FAI; The time to peak ground reaction force in all directions duringlanding in individuals with unilateral FAI was shorter than that of the matching side footin normal person, but slightly longer than those with unilateral FAI contralateral footlanding. During double-foot landing, the each direction peak GRF of both sides inindividuals with unilateral FAI were slightly smaller than that of the matching side inindividuals without FAI, but the time each direction peak GRF of both sides inindividuals with unilateral FAI were slightly longer than that of the matching side inindividuals without FAI.②During the single-foot landing, the maximum degree of kneeflexion and ankle extension in unilateral FAI ipsilateral single landing not only largerthan the matching side foot single landing on normal person, but also larger than that of the contralateral foot landing on unilateral FAI;On the other hand, the time to maximumdegree in knee flexion and ankle extension on unilateral FAI was extremely shorter thanthat of control group, no matter ipsilateral-foot landing or double-foot landing, and themaximum angular velocity of knee flexion and ankle extensorthose with unilateral FAIwere greater than without FAI individuals.③By instantaneous knee-ankle angle of thetime100ms before touchdown and touchdown instant comparison between the twogroups, the ipsilateral of unilateral FAI knee and ankle flexion didn’t actively stretchbefore touchdown, indicating feedforward of neuromuscular control changed, asfeedforward control of contralateral with unilateral FAI remains to be furtherstudied.④During single-foot landing, each direction peak GRF、the maximum degree ofankle inversion and its corresponding time of unilateral FAI were greater than double-footlanding, ankle flexion、 knee extension and its corresponding time were smaller thandouble-foot landing, those showed that double-foot landing was much safer than singlefoot landing.