Relationship Between Lower Extremity Stiffness Charact Eristics And Explosive Force Performance Of Sprinters

Research objectives:To explore the relationship between lower extremity stiffness,explosive performance and sprint performance of sprinters by comparing the vertical stiffness and muscle tendon mechanical characteristics under different loads and jumping forms.Research methods:Ten second-level sprinters performed reverse jump(CMJ)and static squat jump(SJ)with six different loads(0%1RM、10%1RM、20%1RM、30%1RM、40%1RM、50%1RM),respectively.The lower extremity dynamics and muscle tendon mechanics indexes were collected under different motion conditions,and the vertical stiffness of lower extremity was calculated.The results of 30 m,60m and 100 m were measured,and the results of standing long jump and standing triple jump were used to indicate the explosive power of the athletes’ lower limbs.The difference between groups of different load and jumping conditions were compared,and the correlation between the lower limb muscle tendon mechanics index,lower limb stiffness,explosive force and sprint performance was analyzed.Research results:(1)Vertical stiffness of lower limbs: there was no interaction between load and jump form(P>0.05),but the main effect of different loads was significantly different(P<0.05).The vertical stiffness of 50%1RM was 621.93 ± 129.17N/m,547.72 ± 173.41N/m and350.03±152.46N/m higher than that of 10%11RM,20%1RM and 30%1RM,respectively(P<0.01).In SJ jump,30%1RM lower limb vertical stiffness was significantly correlated with30 m,60m,100 m,standing long jump and standing triple jump(P<0.05).In CMJ jump,0%1RM,10%1RM,20%1RM,30%1RM and 50%1RM vertical stiffness of lower limbs were significantly correlated with 30 m,60m,100 m,standing long jump and standing triple jump(P<0.05).There was a significant correlation between vertical stiffness of lower limbs and peak power under 30%1RM load(r=0.92,P<0.01).(2)Muscle tendon characteristics:There were significant differences in the elasticity of Achilles tendon(AT),gastrocnemius medials(GM)and biceps femoris(BF)under different loads(P<0.05).The elasticity of 30%1RM AT was significantly higher than that of 10%1RM,20%1RM and 40%1RM by 0.13±0.04,0.12±0.05 and 0.10±0.04,respectively.GM elasticity of 30%1RM was significantly lower than that of 40%1RM and 50%1RM by 0.14±0.06 and0.12±0.05,respectively.The BF elasticity of 40%1RM was significantly 0.10±0.04 higher than that 50%1RM.AT 10%1RM load,the maximum hardness of AT is 859.90±234.80N/m;at 30%1RM load,the maximum GM hardness is 361.90±98.36N/m;at 30%1RM load,the maximum BF hardness is 421.80 ± 215.46N/m.AT harness under 20%1RM load was significantly correlated with the score of 60m(r=0.68,P<0.050),and AT hardness under40%1RM load was significantly correlated with the score of 100m(r=0.74,P<0.05).GM hardness under 20%1RM load is highly correlated with 30 m performance(r=0.78,P<0.01);GM hardness under 40%1RM load is highly correlated with 60 m performance(r=0.78,P<0.01);GM hardness under 50%1RM load is significantly correlated with 30 m,60m and100 m performance(r=0.70,r=0.72,r-0.70,P<0.05).Research conclusion:(1)The jumping form does not affect the development of lower limb stiffness,and the vertical stiffness of lower limb increase with the increase of weight load.50%1RM is suitable for the training load of lower limb vertical stiffness.(2)The vertical stiffness of lower limbs under 30% 1RM loading condition is most closely related to sprint performance and explosive power performance,and can be used as the appropriate load for continuous rapid wight training.(3)AT hardness at 10%1RM loading condition and GM hardness at 50%1RM loading condition have the greatest influence on the storage and utilization of elastic energy.