The Relationship Between Muscle-tendon Unit Length And Fascicle Length Of The Biceps Femoris Long Head At The Time Of Maximum Strength And The Effect Of Strain

Objective:Muscle-tendon unit length of the long head of the biceps femoris at the time of maximum strength,fascicle length of the long head of the biceps femoris at the time of maximum strength and flexibility score are measures of muscle lengthening ability.The purpose of this study was to determine the relationship between each two measures,and determine the effect of muscle strain injury on this three relationships.Method:22 participants with sprint training experience were recruited,including 11 healthy men and 11 men with hamstring muscle strain injury.Hamstring flexibility were obtained through the passive straight leg raise test.Kinematics and kinetics data were collected during 10°/s isokinetic strength test.GE LOGIQ e musculoskeletal ultrasound was used to measure the muscle fiber structure of the long head of the biceps femoris.Qualisys three-dimensional motion capture system was used to obtain the kinematic data.ISOMED 2000 isokinetic tester was used to obtain the knee flexion moment.All data are collected synchronously.The muscle-tendon unit length and the fascicle length of the long head of the biceps femoris at the time of maximum strength,and the flexibility score were calculated.Paired-sample T test was used to compare the muscle-tendon unit length at the time of maximum strength,the fascicle length at the time of maximum strength and the hamstring flexibility score between the natural take-off leg and the opposite leg in the healthy group,or between the healthy side and the injured side in the injury group.Multiple linear regression analysis with class variables is used to determine the relationship between the muscle-tendon unit length at the time of maximum strength and the fascicle length at the time of maximum strength,between the hamstring flexibility scores and the muscle-tendon unit length at the time of maximum strength,between the hamstring flexibility scores and the fascicle length at the time of maximum strength,and whether these relationships is different between the natural take-off leg and the opposite leg in the healthy group or between the healthy side and the injured side in the injury group.Results:There was no significant difference in muscle-tendon unit length at the time of maximum strength(p=0.099),fascicle length at the time of maximum strength(p=0.816)or hamstring flexibility scores(p=0.777)between the natural take-off leg and the opposite leg in the healthy group.In the healthy group,the muscle-tendon unit length at the time of maximum strength was not related to the fascicle length at the time of maximum strength(R2=0.200,p=0.055),the muscle-tendon unit length at the time of maximum strength was not related to the hamstring flexibility scores(R2=0.031,p=0.474),the fascicle length at the time of maximum strength was not related to the hamstring flexibility scores(R2=0.003,p=0.826).There was no significant difference in muscle-tendon unit length at the time of maximum strength(p=0.312)or hamstring flexibility scores(p=0.797)between the healthy side and the injured side in the injury group.Fascicle length at the time of maximum strength of the injured side was significantly shorter than that of the healthy side(p=0.001).In the injury group,the muscle-tendon unit length at the time of maximum strength was not related to the fascicle length at the time of maximum strength(R2=0.061,p=0.279),the muscle-tendon unit length at the time of maximum strength was not related to the hamstring flexibility scores(R2=0.016,p=0.582),the fascicle length at the time of maximum strength was not related to the hamstring flexibility scores(R2=0.017,p=0.569).Conclusions:The difference in the hamstring flexibility scores,the length of the muscle-tendon unit and the fascicle length at the time of maximum strength of the long head of the biceps femoris between the legs of those without hamstring strain injury varies from person to person.Of those without hamstring strain injury,the hamstring flexibility scores,the length of the muscle-tendon unit and the fascicle length at the moment when the long head of the biceps femoris muscle strength is maximum represent three ability characteristics of the long head of the biceps femoris,there is no significant correlation among them.Within five years after hamstring strain injury,the fascicle length at the time of maximum strength of the long head of the biceps femoris on the strained side is significantly shorter than that of the healthy side,but the sensitivity to damage of hamstring flexibility scores and the length of the muscle-tendon unit at the time of maximum strength of the long head of the biceps femoris varies from person to person.Of those within unilateral hamstring strain injury,the hamstring flexibility scores,the length of the muscle-tendon unit and the fascicle length at the moment when the long head of the biceps femoris muscle strength is maximum represent three ability characteristics of the long head of the biceps femoris,there is no significant correlation among them.