Effect Of Static Stretching On The Muscle Morphology Of Biceps Femoris And Knee Flexor Strength

Purpose The purpose of this study was to use the CONTREX muscle strength test and muscle in vivo ultrasound image measurement to investigate the effect of the static stretching on the morphological changes of the biceps femoris,and evaluate the effect of static stretching on on knee flexor strength output.Methods CON-TREX multi-joint constant velocity force test and training system and the M7 Super ultrasound image were used to collected the Kinetic data and muscle morphology data during isometric contraction,concentric contraction and eccentric contraction before and after the static stretching of biceps femoris,the subject were 27 college students with exercise habits in Shanghai University of Sport.The kinetic data is the relative peak torque,the relative average torque,and the relative total work,ect.Muscle morphology data includes muscle pennation angle and muscle fiber length.Statistical methods were performed using a paired-sample T test with a significant level of P < 0.05.Results(1)After static stretching,the relative peak torque and relative average torque decreased significantly in the isometric contraction;In the concentric contraction and eccentric contraction,relative total power,relative peak power,relative peak torque and relative total work were statistically significant(P<0.05).(2)In the stable phase of isometric contraction,the mean PA angle after static stretching is significantly reduced at the proximal of BFLh(P<0.05).The pennation angles of the isometric contraction stabilization phase and the end of the eccentric contraction were smaller than those before the static stretching,but were not statistically significant.(3)In the stable phase of isometric contraction,the mean muscle fiber length FL increased after static stretching,and the significant difference occurred at the distal of the BFLh(P<0.05).Conclusions Static stretching may cause changes in the muscle morphology of the long head of biceps femoris,such as increasing the length of the muscle fibers and reducing the pennation angle.At the same time,static stretching has the effect of reducing knee flexor strength output and has the potential to prevent muscle strain.