Effects Of Two Kicking Types On Biomechanical Characteristics Of Hamstring Muscles Of Kicking Leg

Objective: To explore the changes of hamstring muscle-tendon length and strain during instep kick and cut-off kick and to analyze the relationship between kicking and hamstring length and activation.Simultaneously determine the phase of the hamstring muscle injury during kicking.Methods: Eleven male professional footballers completed the two kicks respectively.Kinematic and electromyography data were acquired respectively and simultaneously with eight-camera high-speed video capture system(Motion,200Hz)and myoelectric apparatus(Delsys,2000Hz).Results:(1)Muscle-tendon length and strain of each hamstring muscle reached the maximum in the follow-through phase after foot-ball contact,and the elongation velocities of each hamstring muscle were positive in the leg acceleration and early follow-through phase;(2)No significant differences existed in the peak hamstring mescle-tendon length and strain between semitendinosus,semimembranosus and long head of biceps femoris during the two kicks.The peak positive elongation velocities of the semimembranosus was greater than the semitendinosus and long head of biceps femoris during the two kicks(p>0.050).The peak muscle-tendon length and strain of the long head of the biceps femoris were significantly greater during the cut-off kick than during the instep kick(p<0.050).No significant differences existed in the muscle-tendon length and strain of semitendinosus and semimembranosus between the two kicks(p>0.050).No differences existed in the peak elongation velocity of each hamstring muscle between the two kicks(p>0.050).The peak muscle-tendon strain of each hamstring muscle was significant greater than the muscle-tendon strain at the peak elongation velocity(p<0.001)and the peak elongation velocity of each hamstring muscle was greater than the elongation velocity at the peak muscle-tendon strain during the two kicks(p<0.001).(3)The pelvis anteversion angle of the kicking leg at the peak muscle-tendon strain of each hamstring muscle was significantly greater during the cut-off kick than during the instep kick(p<0.050),so as the amount of angle change of the pelvis(p<0.050).(4)There was a significant correlation between the peak muscle-tendon strain of semitendinosus and the hip flexion angle,the knee extension angle and the pelvis anteversion angle at the peak muscle-tendon strain during the instep kinking(p<0.050).There was a significant correlation between the peak muscle-tendon strain of semimembranosus and the knee extension angle and the pelvis anteversion angle at the peak muscle-tendon strain during the instep kinking(p<0.050).And there was a significant correlation between the peak muscle-tendon strain of long head of biceps femoris and the pelvis anteversion angle at the peak muscle-tendon strain during the instep kinking(p<0.050).While there was no significant difference between the muscles-tendon strain of each of the hamstring muscle and each joint angle of kicking leg during the cut-off kicking(p>0.050).Conclusions:(1)The potential for hamstring muscle strain injury exists during the leg acceleration and early follow-through phase because each of the hamstring muscle were in eccentric contractions during the two phases.(2)Hamstring muscle may be more likely to sustain injuries during the cut-off kicking than during the instep kicking especially the long head of biceps femoris for its peak muscle-tendon strain was significantly greater during the cut-off kicking than during the instep kicking.(3)There was a significant correlation between each of the hamstring muscle-tendon strain and the joint angle of kicking leg during the instep kicking while the factors that affect the peak muscle-tendon strain of hamstring muscles may be more complicated during cut-off kicks.