The Effect Of Horizontal And Vertical Lower-limb Plyometric Training On Age-group Swimmer Swimming Track Start Performance

Purposes: Lower Limb plyometric training as a lower limb explosive power training method,is widely used in many sports,which can effectively improve athletes’ lower limb explosive power,sprint ability,and ability to change of direction.The swimming start performance is affected by the combination of the athlete’s strength and conditioning level and technical mastery level,and the lower extremity power is an important factor affecting the swimming start.However,the research on the starting of swimming in lower limbs plyometric training in China is still in its infancy.This study intends to explore the effect of six-week lower limb plyometric training on the starting performance of swimmers in the age group and provide theoretical support for the strength and conditioning training of the athletes in the age group.At the same time,the lower limb plyometric training can be divided into horizontal and vertical directions.The direction of the body’s power is more horizontal when swimming start,so the direction of the lower limb plyometric training needs to be considered in the experimental design.This article will further investigate the effects of lower limb plyometric training in different directions on swimming start.Methods: Nineteen age group athletes（12-16 years old）were randomly divided into three groups: horizontal lower limbs plyometric training group（horizontal training group）,vertical lower limbs plyometric training group（vertical training group）,and a normal swimming control group（normal training group）.The horizontal training group and the vertical training group also performed three times per week on the basis of the regular swimming training for a total of six weeks of horizontal and vertical lower limb plyometric training interventions,while the normal training group only carried out daily swimming training.The swimming training plan for all subjects is guaranteed to be the same as before.Before and after the experiment,swimming start test and land explosive power test were performed.Video was recorded with high-speed camera,and kinematics and dynamics analysis were performed with motion analysis software.Results:（1）There was a significant difference before and after the knee angle experiment in the horizontal training group（p=.015）,but there was no significant difference between the vertical training group and the normal training group（p>.05）;（2）There was a significant difference before and after the kick-off time test in the horizontal training group（p=.005）,and there was a significant difference before and after the kick-off time experiment in the vertical training group（p=.033）,there was no significant difference in the normal training group（p>.05）;（3）There was a significant difference in the horizontal training group before and after the kick off speed experiment（p=.001）,but there was no significant difference in the vertical training group and the normal training group before and after the experiment（p>.05）;（4）There was a significant difference in the horizontal training group before and after the horizontal maximum force value experiment（p=.003）,and a significant difference in the vertical training group before and after the horizontal maximum force value experiment（p=.029）,while there was no significant difference in the normal training group（p>.05）;（5）There was a significant difference in the horizontal training group before and after the flight distance experiment（p=.015）,and there was no significant difference between the vertical training group and the normal training（p>.05）;（6）There was a significant difference in the horizontal training group before and after the standing long jump test（p<.001）,and a significant difference in the vertical training group before and after the long jump test（p=.018）;there was a significant difference in the horizontal training group before and after the countermovement squat jump experiment（p=.024）,there is a significant difference a vertical training group before and after the countermovement squat jump experiment（p<.001）,no significant difference in the normal training group（p>.05）;（7）There was a significant difference in the horizontal training group before and after 5 meters experiment（p<.001）,and a significant difference in the vertical training group before and after the 5 meters experiment（p=.016）,no significant difference in the normal training group（p>.05）.Conclusion: 1.Six weeks of horizontal lower limb plyometric training can increase the angle of the back knee of the swimming ready position.2.Six weeks of horizontal and vertical lower limb plyometric training can reduce the kick-off time,kick-off speed and the maximum force of leaving the stage during the on-block phase of swimming start,and the effect of the horizontal training group is more obvious.3.Six weeks of horizontal lower limb enhancement training can increase the flying distance in flight phase of swimming starts.4.Six weeks of lower limb plyometric training can increase the height of standing long jumps and vertical jumps.The horizontal training group has the most significant effect in standing long jumps;the vertical training group has a positive effect on squat jump and countermovement vertical jump height.5.Six weeks of horizontal and vertical lower limb plyometric training can shorten the time to 5 meters,and the performance of the horizontal training group is more obvious.