| Purpose:Due to the continuous increase in marathon events and the number of participants,people not only benefit from long-distance running,but also sustain injuries caused by running,seriously affecting their lives.Therefore,in recent years,there are many studies on arch deformation and the change of the plantar pressure distributions caused by long-distance running.The stress of lower extremities has direct association with change of arch height.The arch mechanism with different strike patterns is different,which can also cause deformation of foot arch and the changes of plantar pressure,causing RRI.Little is known about the changes in arch height index(AHI)and flexibility in runners with different strikes patterns after marathon running under various load conditions.The purpose of this study was to examine the effects of a marathon run on the AHI,arch height flexibility and plantar pressure of runners with different strike patterns.Methods:33 runners,including 18 forefoot-midfoot strike runners and 15 rearfoot strike runners were included.Before and after the marathon run,dorsal height and truncated foot length of right feet were measured using a 3-D scanner under 10%,50%and 100%of body weight,respectively,and arch height index(AHI)at each of the three loading conditions and arch flexibility at 40%and 90%of body weight were conducted,as well as the plantar pressure parameters of seven foot(contact time,peak force and peak force time)within 30 seconds utilizing a gait analysis treadmill.The changes of each parameter were analyzed by 2×2 mixed design analysis of variance(ANOVA).Results:AHI at 10%body weight significantly decreased after marathon(p<0.01).At 100%of body weight,marathon run and foot strike pattern had an interaction effect(p=0.027).The AHI of the forefoot-midfoot strike runners had no change after running(p=0.436),while the AHI of the rearfoot strike runners decreased significantly after running(p=0.001).Arch flexibility was higher in the rearfoot strike group than in forefoot-midfoot strike group with a 90%body-weight load increase(p=0.024).Post-run contact time were increased under the toes(p=0.041),the mid-foot(p<0.001),the medial heel(p=0.004),and the lateral heel(p=0.004).Post-run peak force decreased under the toes(p<0.001)and the medial forefoot(p=0.002),while increased under the medial heel(p=0.001)and the lateral heel(p=0.001).Post-run peak force time decreased under the toes(p=0.017)and increased under the lateral forefoot(p=0.009)and mid-foot(p=0.006).Conclusion:1.After marathon running,the plantar ligament and fascia were relaxed due to fatigue,which resulted in the decrease of arch height;when the load increased to a certain extent,the muscles were involved to help maintain the arch height;with further load increase,rearfoot strike runners showed greater fatigue in the soft tissues of the feet,which may increase the risk of RRI.2.With a greater load increase,the internal tension of foot soft tissue in rearfoot strike runners was more significant,and they were unable to maintain the original stiffness of the arch,which was more likely to cause the strain of soft tissue and lead to the occurrence of RRI.3.After marathon running,prolonged contact time increased the risk of ankle sprain;the increase of peak pressure in the heel area increased the load on the ankle and tibia;the increased loading rate in the toe region increased the risk of RRI in this region.Recommendations for Future Research:Studies on structure and function of foot arch can also be conducted analyzing the effect of gender,sport level,dynamic and static condition and using deep muscular measurement,in order to better provide theoretical support for the prevention and rehabilitation of RRI in marathon runners. |
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