The Relationship Between Maximal Strength And Stiffness Of Lower-limb And Sprint Performance Of Acceleration And Maximal Speed Phases

Objectives:This study aimed to explore the relationship between maximal strength of lower limb,reactive strength,lower-limb stiffness and the sprint performance of acceleration and maximum speed phases.Methods:Sixteen high-level male sprinters were tested for 50-meter sprint,45cm drop jump,and isometric mid-thigh pull(IMTP)to obtain the kinematics results of the acceleration and maximal speed phases,as well as reactive strength(reactive strength index,reactive strength ratio),lower-limb stiffness(absolute and relative vertical stiffness,knee and ankle joint stiffness),maximal strength and basic variables,etc.Pearson correlation analysis were used to analysis the relationship between the kinematics index of sprint and maximal strength,reactive strength and lower-limb stiffness.Results:(1)Force at 150ms,200ms,250ms,0-150ms,0-200ms,0-250ms force development rate and maximal strength showed moderate negative correlation with the 5-15m time(p<0.05,r:-0.32～-0.43),but were not related to 35-45m time(p>0.05).Reactive strength index and reactive strength ratio were not related to 5-15m time(p>0.05),but showed moderate negative correlation with 35-45 time(p<0.05,r:-0.33--0.34).There were no significantly relationship between each index of lower limb stiffness and 5-15m and 35-45m time(p>0.05).(2)The contact time of acceleration phase showed negative large correlation with 150ms,200ms and 250ms force,0-150ms,0-200ms and 0-250ms force development rate(p<0.05,r:-0.52～-0.63).The contact time of maximal speed phase showed negative moderate correlation with 150ms and 200ms force,0-150ms and 0-200ms force development rate(p<0.05,r:-0.31～-0.45).For acceleration and maximal speed phases,the relative stride length showed moderate correlation with force at 200ms,250ms,the force development rate in 0-200ms and 0-250ms(p<0.05,r:0.33～0.46).Relative stride length of acceleration phase showed large correlation with maximal strength(p<0.05,r=0.50).For acceleration and maximal speed phases,there were no significantly relationship between flight time,step frequency,absolute stride length and maximal strength and variables(p>0.05).(3)Reactive strength index and reactive strength ratio showed negative moderate correlation with contact time of acceleration phase(p<0.05,r:-0.40～-0.49),but showed very large correlation with contact time of maximal speed phases(p<0.05,r:-0.84～-0.88),and showed moderate correlation with step frequency of maximal speed phase(p<0.05,r:0.36～0.38),and showed no significantly correlation with others gait indexes(p>0.05).(4)For acceleration and maximal speed phases,relative and absolute vertical stiffness showed very larger correlation with contact time(p<0.05,r:-0.84～-0.89),and showed large correlation with step frequency(p<0.05,r:0.60～0.68)and relative stride length(p<0.05,r:0.51～0.58).For acceleration and maximal speed phases,relative and absolute ankle and knee joint stiffness showed negative large correlation with contact time(p<0.05,r:-0.52～-0.68).Relative and absolute ankle joint stiffness showed very large correlation with step frequency of acceleration phase(p<0.05,r:0.80～0.88),and showed large correlation with step frequency(p<0.05,r:0.58～0.65).There were no significantly relationship between others gait indexes and lower-limb stiffness(p>0.05).Conclusion:(1)1For elite sprinters,the force-time curve is moderately negatively correlated with the performance of acceleration phase,and the reactive strength is moderately negatively correlated with the performance of maximum speed phase.(2)The contact time in the acceleration phase is highly negatively correlated with the force-time curve,and the contact time at the maximum speed phase is moderately negatively correlated with the force-time curve.(3)The relative stride length of the acceleration phase and the maximum speed phase is positively correlated with the force-time curve,and the relative stride length of the acceleration phase is highly positively correlated with the maximum strength of the lower limbs.(4)The reactive strength is moderately negatively correlated with the contact time during the acceleration phase,and is highly negatively correlated with the contact time during the maximum speed phase.And the reactive strength is positively correlated with the step frequency in the maximum speed phase.(5)For the acceleration phase and the maximum speed phase,the vertical stiffness is highly negatively correlated with the contact time,and highly positively correlated with the step frequency(p<0.05,r:0.60～0.68)and the relative stride length.(6)For the acceleration phase and the maximum speed phase,the stiffness of the ankle and knee joints are highly negatively correlated with the contact time.The ankle joint is highly positively correlated with the step frequency during the acceleration phase,and highly positively correlated with the step frequency during the maximum speed phase.