Acute Effects Of Combined Stretching Training On The Hamstring Performance Of Female Soccer

OBJECTIVE: To explore the acute effects of combined stretching training on the performance of female football soccer,and provide theoretical basis for the application of combined stretching training.METHODS: Thirty-three female soccer players from Xi'an Physical University were randomly divided into control group(CG,N=10),static stretching group(SSG,N=11),and combined stretching group(CSG,N=12).There were no stretching training in CG group and there were just stretching hamstring for 20 s in SSG group.In CSG group,hamstring of players was stretched for 20 s and then was performed 10 quick hooks.Two experiments were carried out during 6 independent days.Part One: The Surface Electromyography(SEMG)was used to test the hamstring muscle discharge before and after the intervention.IEMG and RMS of SEMG were selected in this experiment.The ISOMED 2000 was used to test the peak torque and work of the hamstring.Part Two: Before and after the intervention,the subjects underwent a sudden turn to the emergency stop.During this period,the high-speed photography was adopted to collect the motion data.At the same time,the three-dimensional force machine was used to test the lower limbs' force and the SEMG was used to test the discharge of the hamstrings during the emergency stop,The rapid transit and emergency stop were divided into three stages,which included emergency stop,rapid turn and off-site.The effects of stretching training on the contraction of the hamstring muscle in the emergency stop were analyzed.RESULTS:Part One: Compared with pre-intervention,the flexibility,maximum work and peak torque of hamstring were increased(P < 0.05),the values of IEMG and RMS were increased in SSG group(P < 0.05),and values of IEMG and RMS were higher than those of CSG group(P < 0.05).Compared with pre-intervention,the flexibility,peak torque,maximum work and total work of hamstring were increased(P < 0.05),but the changes of IEMG and RMS were not significant in CSG group(P > 0.05).Part Two: The peak value of the first force on the lower limbs of CSG and SSG group decreased significantly during the period of rapid stop(P< 0.05).The electromyography results of hamstring showed that IEMG increased and RMS decreased in SSG group(P > 0.05).There were no significant changes of RMS values in CSG group,but there was an increasing trend in IEMG values(P > 0.05).The values IEMG and RMS of SSG group showed a decreasing trend(P > 0.05).However,IEMG and RMS in CSG group showed an upward trend(P > 0.05).There were no significant changes in the peak value of the second force of lower limb stress of CSG group and SSG group in the off-ground stage(P > 0.05).In the electromyography results of hamstring also showed that the values of IEMG and RMS decreased in SSG group(P > 0.05),The values of IEMG and RMS decreased in CSG group(P > 0.05).CONCLUSION:Part One:(1)Both static stretching training and combined stretching training could improve the ductility of hamstring muscle immediately,and the acute effects of combined stretching training on hamstring performance were similar to those of static stretching training.(2)The peak torque was increased immediately after static stretching training,and the immediate explosive force of muscle was also increased,but there was no difference of the output work of muscle between before and after stretching.(3)The peak torque and work ability of hamstring muscle were increased immediately after combined stretching training.The instant explosive force and muscle output power of the female soccer athletes could be improved,which might provide evidence of appliancation of combined stretching training for the female soccer.Part Two:(1)After the combined or static stretching,the force of lower limb of the emergency stop stage were reduced when the emergency stop action was carried out,and the effects of combined stretching or the static stretching were similar.(2)After the static stretching,the IEMG value of the emergency stop stage were increased,and the valued of RMS showed a descending trend,which indicated that the movement unit of the roping muscle in the motion might be reduced,but the total discharge amount were increased,which might means that there were increased risks of injury of hamstring during sports.The results of IEMG and the RMS in acute rotation phase showed a descending trend,The IEMG and RMS in the ground phase were decreased and contraction ability of the hamstring was reduced which was damage for dynamic stability of the knee joint.(3)After the combined stretching training,the values of IEMG and RMS in the emergency stop stage and relative contractive force of hamstring were increased.The results of IEMG and RMS in the acute rotation stage showed upward trend.Meanwhile,the contraction ability of the hamstring was increased,which could bettermaintaine the stability of the knee joint;The decrease of IEMG and RMS in the ground phase were observed,and the contraction ability of the hamstring was decreased.It is suggested the combined stretching training could be adopted by female soccer athletes,and this method still need be further studied in the field of injury prevention.