| Objective: To compare the effects of self-designed and self-manufactured novel prophylactic ankle brace(Chinese parachute ankle brace,CPAB)and two ordinary ankle braces on biomechanical assessment of the ankle joint during half-squat parachute landing.In order to prevent and reduce the injury of paratroopers’ ankle joints during the half-squat landing.Methods: Based on preliminary epidemiological survey on paratroopers’ ankle injury mechanisms and ankle biomechanical characteristics during half-squat parachute landing of our research group,we designed and developed CPAB,then performed biomechanical tests on it.20 elite paratroopers,were in four different ankle brace conditions(no-brace,elastic brace,semi-rigid brace,CPAB),respectively.Each participant was instructed to jump off a platform with three different heights of 40 cm,80cm and 120 cm respectively,and land on the AMTI force plate in a half-squat posture.The AMTI force plate recorded and calculated kinetic data,such as vertical ground reaction force(vGRF)and time to peak vGRF(T-PvGRF).Vicon 3D motion captured system recorded ankle kinematic data,including angular displacement of maximal dorsiflexion(MDAD),angular velocity of maximal dorsiflexion(MDAV)and angular displacement of maximal inversion(MIAD),angular velocity of maximal inversion(MIAV).The AnyBody musculoskeletal model of half-squat parachute landing was established in the AnyBody Modeling System.Importing kinematic data and driving the model,then analyzing the kinetic parameters of ankle joint with the technologies of computer simulation and inverse dynamics,for example,maximal plantarflexion moment(MPM),maximal eversion moment(MEM),work and peak power of ankle joint.After the experiment,all the participants completed the self-designed questionnaires.All the experimental data were analyzed by ANOVA and paired t test,and P < 0.05 was considered statistically significant.Result: 1.With the increase of dropping height,peak vGRF,MDAD,MDAV,MIAD,MIAV,MPM,MEM,work and peak power of ankle joint all increased significantly(P<0.001),however,the T-PvGRF decreased(P<0.05).2.When at the same dropping height of 120 cm,compared with the no-brace group,three braces can all slightly increase vGRF and there was no significant difference on vGRF of each group(P=0.237);three braces can all reduce T-PvGRF,and the elastic brace and CPAB can both reduce T-PvGRF with 6—10ms;3.All the three ankle braces can significantly decrease the MDAD,MDAV and MPM,thus maintaining the motion stability of the ankle joint in sagittal plane,and compared with elastic brace,CPAB and semi-rigid brace restrict dorsiflexion more efficiently(P<0.05).Similarly,all the three ankle braces can significantly decrease the MIAD,MIAV and MEM,therefore maintaining the motion stability of the ankle joint in coronal plane,according to the reducing extent of inversion from large to small was CPAB,semi-rigid brace and elastic brace.4.Wearing semi-rigid brace or CPAB both significantly reduced ankle work(t=3.331,P<0.01;t=5.107,P<0.001)and peak power(t=6.711,P<0.001;t=7.237,P<0.001),and CPAB performed more efficiently than semirigid brace.While elastic brace had no significant effect on energy parameters(P>0.05);5.The total scores of results were elastic brace: 21.91±3.25;semi-rigid brace 19.20±2.99 and CPAB: 23.37±3.08.85% participants acknowledged that CPAB can prevent excessive inversion and eversion than elastic brace,and it was more comfortable and soft than semirigid brace.Conclusion: 1.Due to the greater extent of dorsiflexion and inversion of the ankle joint during half-squat parachute landing,we designed manufactured novel parachute ankle brace CPAB,which had a significant effect on restricting motion of the ankle joint in coronal and sagittal planes.2.The kinematic and kinetic tests showed that with the increase of dropping height,the easier would the ankle becomed excessively dorsiflexion and inversion during half-squat parachute landing,further resulting in ankle injury.The CPAB and semi-rigid brace can restrict dorsiflexion more efficiently than elastic brace,thus maintaining the motion stability of the ankle joint in sagittal plane;The CPAB restricted inversion more efficiently than semi-rigid brace and elastic brace,further enhancing the motion stability of the ankle joint in coronal plane 3.The energy test showed that with the increase of dropping height,more work and peak power the ankle applied during half-squat parachute landing.Wearing semi-rigid brace or CPAB both significantly reduced ankle work and peak power,with CPAB more efficient.4.The elastic brace is more comfortable and soft with complexity in wearing;the semi-rigid ankle had greater stability and restricted the activity of the ankle joint effectively,but its constriction was heavy;while the CPAB combined the advantages of above two ankle braces,and it had the advantages of novel appearance,high efficiency and superior comfort.Therefore,it provided a reliable choice for parachute jumping and training in China. |
