Acute Effects Of Hamstrings Stretching On Biomechanical Performance Of Female Athletes During Cutting

Objective:The purpose of this study is to investigate the acute effects of hamstring static stretching on kinematics and kinetics and surface EMG in female athletes during cutting, then discuss its influence on the factors associated with ACL injury. Methods:Twelve female athletes from Shanghai University of sport completed cutting task both before no stretching and hamstrings static stretching in two days. The 3D motion data, ground reaction forces and surface EMG date were recorded and analyzed during the cutting process. Paired T-test was applied to compare the statistical difference between no stretching and hamstring static stretching. Results & Discussion:(1) Compared with the no stretching, there were significant increases in the range of motion of hip in sagittal plane after hamstrings static stretching(p=0.041). Also, there were significant increases in the range of motion of knee in frontal plane(p=0.049). After stretching, the initial-contact knee angle significantly decreased(p=0.046) and the peak value of ankle varus significantly decreased(p=0.037) comparing with no stretching. These results indicates a negative affection on motion performance(2) Compared with no stretching, there was a significant differences in the timing of stance-phase peak vertical ground reaction force(p=0.032), peak vertical ground reaction force occurred later after being stretched. Besides, the exterior tibia shear force(ETSF) significantly decreased after being stretched(p=0.036). All this reveals that hamstring static stretching may potentially decrease the risk of ACL injury during cutting.(3) Our results determined that the aEMG of biceps femoris during the initial stage of cutting significantly decreased after hamstring static stretching(p=0.033). that subjects were more dependent on hip muscles during initial stage of cutting. Conclusions:Hamstrings stretching not only affects the motion performance of cutting, but also potentially reduces the risk of ACL injury.