Effects Of Transition To Forefoot Strike On Running Economy And Lower Extremity Asymmetry

Purpose:The purpose of this study was to compare the running economy and lower extremity asymmetry of habitual rearfoot strike（RFS）runners when running with RFS and forefoot strike（FFS）,and to observe the relationship between running economy and lower extremity asymmetry.Methods:A total of 20 male recreational runners were recruited for this study,and15 habitual rearfoot landing runners were finally included after screening.Subjects were asked to run in rearfoot strike（RFS）and forefoot strike（FFS）mode at speeds of3.0m/s,3.5m/s and 4.0m/s,respectively.In this study,a C-13 infrared motion capture camera（120Hz,C-13,STT,Spain）was used to capture lower limb joint angles,and3DMA optical motion capture analysis software was used to calculate and extract lower limb joint angles;a K4b2（COSMED,Rome Italy）was used to capture the oxygen uptake（VO₂）and the contribution of oxygen uptake and carbohydrate contribution to total energy expenditure（%CHO）.VO₂ and%CHO data were calculated and extracted using K4b2 gas analysis software,with lower oxygen uptake representing the better running economy.Data were statistically analyzed using SPSS 26.0 software,and two-way repeated measures ANOVA was performed for all lower limb joint angles,symmetry angles and running economy data,the significance level was p<0.05;in addition,Person correlation analysis was performed for lower limb asymmetry parameters at the moment of foot touch and toe off the ground,respectively,and running economy parameters,the significance level was p<0.05.Results:1.Running economy:（1）Oxygen uptake:oxygen uptake（VO2）in forefoot strike（FFS）was 6.8%（P=0.038<0.05）greater than VO2 in rearfoot strike（RFS）at 3.0m/s,and 1.46%（P=0.524）and 4.46%（P=0.032<0.05）lower than VO2 in RFS at 3.5m/s and 4.0m/s,respectively.When running with FFS,VO2 was 6.93%（P=0.138）greater at 3.5m/s than at 3.0m/s;15.19%（P<0.001）greater at 4.0m/s than at 3.0m/s;and 7.72%（P=0.048<0.05）greater at 4.0m/s than at 3.5m/s.When RFS running was used,VO2 at3.5m/s was 15.90%（P=0.001<0.05）greater compared with 3.0m/s;VO2 at 4.0m/s was28.77%（P<0.001）greater compared with 3.0m/s;and VO2 at 4.0m/s was 11.10%（P=0.001）greater compared with 3.5m/s.（2）Carbohydrate contribution to total energy expenditure（%CHO）:FFS resulted in 4.89%（P=0.716）,13.86%（P=0.061）and 15.77%（P=0.002<0.05）higher%CHO compared with RFS at 3.0m/s,3.5m/s and 4.0m/s,respectively.When running with FFS,%CHO was 18.25%higher at 3.5m/s compared with 3.0m/s（P=0.718）;%CHO was 87.27%higher at 4.0m/s compared with 3.0m/s（P<0.001）;and%CHO was 58.37%higher at 4.0m/s compared with 3.5m/s（P<0.001）.When running with RFS,%CHO was 8.93%higher at 3.5m/s compared with 3.0m/s（P=1.000）;%CHO was 69.67%higher at 4.0m/s compared with 3.0m/s（P=0.003）;%CHO was 55.75%higher at 4.0m/s compared with 3.5m/s（P<0.001）.2.Asymmetry of lower extremity:（1）Symmetry angle（SA）of the lower extremity joints at the moment of foot-contact:when the speed was 3.5m/s,the knee internal/external rotation SA of FFS was significantly greater compared with RFS（P<0.05）;when the speed was 4.0m/s,the ankle internal/external rotation SA of RFS significantly greater compared with FFS（<0.05）.When running with FFS,the hip internal/external rotation SA at 3.0m/s was significantly smaller compared with 3.5m/s（P<0.05）,both ankle internal/external rotation SA（P<0.05）and ankle internal/external rotation SA（P<0.05）at 3.5m/s were significantly greater than 4.0m/s,respectively.When running with RFS,the hip internal/external rotation SA at 3.0m/s was significantly smaller compared with 3.5m/s（P<0.05）.（2）SA of the lower extremity at the moment of toe-off:When the speed was 3.0m/s,the ankle dorsiflexion/plantarflexion SA of FFS was 73.79%greater compared with RFS（P<0.05）;The FFS resulted in 94.33%greater ankle dorsiflexion/plantarflexion SA（P<0.05）,132.06%greater ankle inversion/extrusion SA（P<0.05）and 47.28%smaller foot angle SA（P<0.05）at 3.5 m/s compared with RFS;The FFS resulted in29.44%smaller hip adduction/abduction SA（P<0.05）and 81.18%greater ankle dorsiflexion/plantarflexion SA（P<0.05）at 4.0m/s compared with RFS.When running with FFS,the hip adduction/abduction SA was 62.57%greater at 3.5m/s compared with4.0m/s（P<0.05）;When running with RFS,the hip internal/external rotation SA and foot angle SA at 3.5 m/s were 20.56%（P<0.05）and 38.87（P=<0.05）smaller compared with4.0m/s,respectively.3.The correlation between lower extremity asymmetry and running economy:Using Pearson correlation analysis,it was found that only ankle rotation SA and RE were correlated（R=-238,P=0.024<0.05）at the moment of foot-contact.Hip flexion/extension SA was correlated with%CHO（R=-216,P=0.024）<0.05,while other SAs and REs showed no correlation.At the moment of toe-off,pelvic tilt SA was correlated with RE（R=266,P=0.011<0.05）;hip adduction/abduction SA（R=-244,P=0.021<0.05）and foot angle SA（R=0.228,P=0.036<0.05）were correlated with%CHO,while no other SAs correlated with either RE or%CHO.Conclusion:（1）Immediate transition to forefoot-strike running does not have an economy advantage at slow and medium speeds but a better economy at faster speeds.（2）The immediate transition to forefoot strike,whether at the moment of foot-contact or toe-off,affected only a small proportion of the symmetrical angle of the lower limb joints.Overall,the effect of the foot strike pattern on the asymmetry of lower limb joint angles was small.（3）Running economy has a weak correlation only with a few symmetry angles of lower extremity joints,and almost no correlation with the symmetry angle of lower extremity joints.