Effects Of Different Foot Strike Patterns On Lower Extremity Biomechanics During Running

Objective: Running is one of the most popular sports.However,a high incidence of sports injuries occurs among runners.Different foot strike patterns use different biomechanical mechanisms of the lower limbs,which may affect the incidence of sports injuries.However,studies on the lower extremity biomechanics of different foot strike patterns are often conducted on the sagittal plane.Three-dimensional(3D)biomechanical studies are limited.The purpose of this study is to explore the basic regular characteristics of the 3D kinematic and kinetic variables of the lower extremities of the human body during running.It also aims to further reveal the effects of different foot strike patterns on the musculoskeletal function and running injury of lower extremities,thereby providing a realistic guidance for running exercises.Methods: A total of 60 male recreational runners were recruited.They were divided into habitual forefoot strikers(hFFS)and habitual rearfoot strikers(hRFS)according to the strike index.Each group consisted of 30 people.The 3D kinematic and kinetic data during running of all the subjects were collected using a Vicon motion capture system(200 Hz,Vicon T40,Oxford,UK)and Kistler force plates(2000 Hz,Kistler Instruments Corp.,Switzerland).The data were further processed using visual 3D software and expressed as mean ± standard deviation.Statistical analysis was performed using SPSS 20.0 software.Kinematic and kinetic data were analyzed using an independent sample T-test.The significance level was set at p<0.05,and the effect size(ES)and 95% confidence interval(CI)of the mean difference(95% CI)were calculated to quantify the difference.Results:(1)Joint angle: The hFFS group had higher hip flexion(p=0.008,ES=0.71,95% CI 2.25° to 14.14°)and adduction angle(p=0.022,ES=0.61,95% CI 0.37° to 4.45°),knee flexion(p=0.001,ES=0.89,95% CI-8.55° to-2.26°)and inversion angle(p=0.035,ES=0.56,95% CI 0.13° to 3.25°),and ankle plantar flexion(p<0.001,ES=3.19,95% CI-28.92° to-20.86°)and internal rotation angle(p=0.010,ES=0.69,95% CI 0.85° to 5.95°)than the hRFS group during initial contact.In addition,hFFS had higher hip flexion angle(p=0.005,ES=0.75,95% CI 2.74° to 14.70°),ankle plantar flexion(p=0.012,ES=0.68,95% CI-8.18° to-1.07°)and inversion angle(p=0.001,ES=0.89,95% CI 1.80° to 6.74°),and ankle coronal plane ROM(p=0.041,ES=0.54,95% CI 0.14° to 6.59°),as well as lower hip abduction angle(p=0.022,ES=0.61,95% CI 0.30° to 3.66°),knee extension angle(p=0.041,ES=0.54,95% CI-6.12° to-0.13°),and ankle dorsiflexion(p=0.003,ES=0.81,95% CI-8.36° to-1.86°)and internal rotation angle(p=0.039,ES=0.55,95% CI-6.87° to-0.19°)than hRFS in the gait cycle.(2)Joint angular velocity: The hFFS group had higher hip flexion angular velocity(p=0.020,ES=0.62,95% CI 5.72°/s to 64.93°/s),ankle dorsiflexion(p<0.001,ES=2.67,95% CI 342.46°/s to 509.28°/s),and inversion(p=0.017,ES=0.64,95% CI 16.30°/s to 154.18°/s)and eversion angular velocity(p=0.030,ES=0.58,95% CI-259.46°/s to-13.73°/s),as well as lower hip adduction angular velocity(p=0.001,ES=0.88,95% CI-100.98°/s to-26.37°/s)and knee flexion angular velocity(p<0.001,ES=1.13,95% CI 60.76°/s to 164.23°/s)than the hRFS group.(3)Joint moment: The hFFS group had higher knee flexion(p<0.001,ES=1.64,95% CI-1.06 Nm/kg to-0.55 Nm/kg)and ankle plantar flexion moment(p<0.001,ES=1.22,95% CI-0.77 Nm/kg to-0.31 Nm/kg),as well as lower knee extension(p=0.045,ES=0.53,95% CI-0.61 Nm/kg to-0.01 Nm/kg,and ankle dorsiflexion moment(p<0.001,ES=2.50,95% CI-0.35 Nm/kg to-0.23 Nm/kg)than the hRFS group.(4)Ground reaction force: The hFFS group had higher anterior ground reaction force(p=0.023,ES=0.60,95% CI 0.004 BW to 0.06 BW)and lower lateral ground reaction force(p=0.008,ES=0.71,95% CI 0.01 BW to 0.06 BW)than the hRFS group.Conclusion:(1)Some differences in kinematics are observed between the two types of foot strikers.Forefoot strikers have higher ankle plantar flexion angle than rearfoot strikers during initial contact,as well as ankle inversion and eversion angular velocity,which increase the risk of ankle sprain.Rearfoot strikers have lower knee flexion angle than forefoot strikers during initial contact,which increases the patellofemoral joint load,ultimately causing knee injury.(2)Some differences in kinetics are observed between the two types of foot strikers.Forefoot strikers have higher ankle plantar flexion moment than rearfoot strikers,indicating that they use their ankles to absorb the impact.However,rearfoot strikers have higher knee extension moment than forefoot strikers,indicating that their knees are overloaded.In addition,forefoot strikers may increase the risk of stress fracture of the metatarsus because of the excessive horizontal impact of the forefoot.