Forward Dynamic And Finite Element Analysis Of Barefoot And Shod Gait Of Young Adults

Objective: Walking and running are fairly popular with people,and these two sports are closely related to sports shoes.Recent years,barefoot sports have become more and more popular.Some scholars believe that being barefoot is the most natural state of Homo sapiens,and wearing shoes leads to decreased foot function and even sports injuries.However,the current research on barefoot and shod gait is still insufficient,and the effect of wearing shoes on gait and related sports injury mechanisms are still unclear.In this study,the biomechanical analysis of barefoot and shod walking and running gait was carried out through plantar pressure analysis and forward dynamic methods.On this basis,the finite element method is used to analyze the foot stress distribution in different strike patterns during barefoot and shod running,which provides a theoretical basis for sports injury prevention.Method: Fifty-four healthy young people were selected for this study,and gait data were collected in barefoot and shod conditions.Gait constraint equations for gait parameters in a stride cycle were established based on D'Alembert principle.And gait kinetic equations were established based on the principle of least action of gait(gait constant).In this study,the body weight of subject was standardized,the stride cycle was normalized,and gait parameters were statistically analyzed.Through the gait constants,vertical ground rebound force,center-of-mass acceleration,velocity,displacement and mechanical energy were calculated using forward dynamics method.The walking and running gait parameters in barefoot and shod states were compared and analyzed statistically.Through the change process of plantar pressure,the foot strike patterns were classified.The foot strike patterns of barefoot and shod running were recorded and analyzed.Furthermore,the fossil foot bones of Homo naledi were restored and the arch of Homo naledi was reconstructed.This foot model served as an ideal model of the foot arch(never wearing shoes).Based on the ideal model,finite element analysis was used to explore the best strike pattern during running.A special subject was trained to run in different strike patterns,the differences in gait parameters of different strike patterns during running were collected and the forward dynamic analysis was carried out.Results: 1)Gait parameters: Compared with being barefoot,the step length,and speed of shod walking are significantly increased(p<0.01);compared with being barefoot,the step length of shod running is significantly increased(p<0.01),the step frequency is significantly reduced(p<0.01),and the COP variabilities in both lateral and anteriorposterior directions increase(p<0.01).2)Gait cycle: Compared with being barefoot,the load response period and the double support phase increase when walking with shoes(p<0.05),the single support phase decreases(p<0.05),and the proportion of the support phase increases significantly(p<0.01).There is no significant difference in the proportion of support phase and swing phase between shod and barefoot running.3)Forward dynamics analysis: Compared with shod walking,the peaks and valleys of the forward dynamic parameters of barefoot walking and the positions of these peaks in stride cycle are quite different.The difference between the two peaks in the ground rebound force(VGRF)of hump chart is smaller when walking barefoot than shod walking,and the difference between the peak and valley values is also significantly smaller when walking barefoot.Compared with shod running,the peaks and valleys of the forward dynamic parameters of barefoot running and the positions of these peaks in stride cycle are quite different.In addition,the energy consumption of shod gait is greater than that of barefoot gait.4)Finite element analysis: wearing shoes can effectively reduce the peak pressure of the three strike patterns,but the equivalent stress peak value of the metatarsal of rear-foot strike pattern in shod state is greater than that of the barefoot state.The three strike patterns of barefoot and shod state have little effect on the peak equivalent stress of the midfoot bone.The stress is concentrated on the outer side of the distal articular surface of the cuboid bone and the distal articular surface of the medial cuneiform bone.The equivalent stress peak of the foot structure of the LFS is the least affected by barefoot and shod states,and the equivalent stress peak is relatively stable.5)After training,the subject ran barefoot in three strike patterns: the stride length of forefoot strike pattern is 213 cm,the stride length of rear foot strike pattern is 210 cm,and that of lateral foot strike pattern is 223cm;the velocity of rear and forefoot strike patterns are both 10.30km/h,while the velocity of lateral foot strike pattern is 10.70km/h,which is a 3.88% increase in velocity.Conclusions: 1)The gait results showed that the variability of the COP increased in both the medial-lateral and anterior-posterior direction when running with shoes,which means that the stability of the human body decreases when running with shoes;2)Through deductive reasoning and experimental simulation,it was discovered that not only walking but also running follows the principle of least action.which lays the foundation for establishing a universal gait dynamics equation;4)The VGRF peaks of walking and running after wearing shoes migrated backward in the stride cycle,which indicated that wearing shoes had an effect on the overall gait pattern;5)The finite element analysis results of the "ideal" model presented that the influencing factors of shod and barefoot state had little impact on the paradigm equivalent stress of the arch and ligament fascia under the LFS.LFS is a more stable strike pattern than the other two patterns.LFS had smaller equivalent stress peak of foot bones than FFS,therefore,It is a safer strike pattern;6)In daily life,there is no uniform strike pattern for healthy young people,whether in barefoot or shod condition.The trained professional runners demonstrated that the ergonomics of the lateral arch strike pattern is the best,which is corroborated with the results of the finite element analysis.