| Research background: With the development of today’s butterfly arm and leg coordination technology,from the beginning of the butterfly stroke with the arm,to the breaststroke with the two legs,to the next two or three hand strokes of the butterfly leg with the large fluctuation of the trunk,and to the present day,the butterfly arm and leg coordination technology is developing in a more economical and reasonable direction with the passage of time,On the other hand,it shows that the coordination of butterfly legs is the key,difficult and characteristic of butterfly technology,and the most critical technical points are the timing and rhythm of coordination.Therefore,in order to improve this technology,it is necessary to make an accurate evaluation of this technology.The research on the coordination of the arm and leg in butterfly stroke at home and abroad mostly focuses on the analysis of the arm or leg movements alone,while the relevant research on the coordination technology of the arm and leg is not clear.The purpose of the study is to explore the differences in the arm-leg coordination techniques of different level athletes in the short distance butterfly stroke,summarize the advantages and characteristics of the timing and rhythm of the high-level athletes in the short distance butterfly stroke through quantitative analysis,and provide data support for the research of the arm-leg coordination techniques in the short distance butterfly stroke in China.Research methods: This experiment selected 10 male first-level athletes age 19 ±3 years,height 180 ± 5.1(cm),weight 73 ± 9.28(kg),FINA score(599 ± 42.75)and 8 male second-level athletes age 18 ± 4 years,height 176 ± 39.18(cm),weight66 ± 16.21(kg),FINA score(449 ± 18)to participate in the test.Through the use of test method,image analysis method and other research methods,the kinematics characteristics of arm-leg cooperation technology of men’s butterfly swimmers at different levels during the mid-course swimming were studied,and the kinetic parameters of athletes such as joint angular velocity and linear acceleration were obtained by the Swedish Qualysys 3D motion capture system for comparative analysis.Research results:In the catching stage of the short distance butterfly,the synchronous index(T1)(p=0.003 < 0.01)of level 1 and level 2 are both negative,and the level 1 is greater than level 2,which is closer to the zero range,and the peak value of the knee joint angular velocity of the first kick of level 1(p=0.005 < 0.05)is greater than level 2;The instantaneous angular velocity of knee joint at the moment of arm entering water(p=0.02 < 0.05)is less than the second level and has significant difference.The difference of the first level(p=0.00 < 0.01)is less than the second level,which is very significant difference,;There was a significant difference in the percentage of stroke time(p=0.009 < 0.01)in the water catching stage,while there was no significant difference in the percentage of downplay time(p=0.08).The vertical amplitude(p=<0.001)and downplay speed(<0.001)of the first level were significantly higher than those of the second level,and the dispersion coefficient of downplay time(0.04 < 0.16),vertical amplitude(0.05 < 0.25)and downplay speed(0.07 < 0.08)of the first level athletes were lower than those of the second level athletes.In the stroke stage of the short distance butterfly,the synchronous index(T2)(p<0.001)of the first and second levels were both negative and the first level was closer to the zero range,and the instantaneous angular velocity of the knee joint(p=0.039 < 0.05)of the first and second levels were both negative and the first level was less than the second level;In the stroke stage,the percentage of stroke time(p=0.001 < 0.01)of the first level is greater than that of the second level,and the percentage of the first lift(p=0.07)of the first level and the second level has no difference,but the dispersion coefficient of the first level is less than that of the second level(0.07 < 0.32).In the upper stroke stage of the short distance butterfly,the synchronous index(T3)(P=0.002 < 0.01)of the first and second levels is positive,and the first level is less than the second level and closer to the zero range,but there is room for improvement.The linear acceleration peak sequence of the first and second level of the hip,knee and ankle joints is from the hip joint(p<0.001)to the knee joint(p=0.003 < 0.01)to the ankle joint(p=0.001 < 0.01),and the first level is greater than the second level;The time difference between the peak acceleration of the hip and knee(p=0.003 < 0.01)is greater than that of the second level,and the time difference between the peak acceleration of the knee and ankle(p=0.021 <0.01)is less than that of the second level.There is no difference in the proportion of the time of the upper stroke stage,the time of the lower stroke and the vertical amplitude,the speed of the lower stroke(p<0.001)of the first stage is faster than that of the second stage,and the dispersion coefficient is less than that of the second stage.There is no significant difference between the first-level and second-level synchronization index(T4)in the air arm transfer stage of the short-distance butterfly,which means that there is no significant difference in the timing of the first-level and second-level arm and leg cooperation in the arm transfer stage,There is no difference in the proportion of arm shifting time between the first level(0.32 ±0.02)and the second level(0.33 ± 0.02),and the proportion of lifting time between the first level(0.30 ± 0.02)and the second level(0.27 ± 0.07).Research conclusion:1.In the water catching stage of the short distance butterfly,the timing and rhythm of the arm-leg cooperation of the first-level athletes are better than that of the second-level athletes.The T1 of the first-level athletes is closer to the zero interval,which makes the arm-leg cooperation more synchronous,and the propulsion force more continuous.At the same time,it reaches the maximum value of the knee joint angular velocity after entering the water,which can bring longer propulsion time;The first stage has a relatively short time of catching the water and a higher speed of the first downplay,which reflects that the better coordination rhythm increases the propulsion effect and makes the curve rise gradually,thus strengthening the propulsion effect.2.In the inner stroke stage of the short distance butterfly,the rhythm and timing of the arm and leg coordination in the inner stroke stage of the first level is better than that of the second level,and the coordination of the arm and leg in the inner stroke stage of the first level is closer to synchronization with T2,which greatly improves the propulsion continuity of the arm in the inner stroke stage;The first level starts early,relatively prolongs the stroke time,and maintains a more streamlined posture of the body by accelerating the speed of leg lifting,controlling the distance of lifting,reducing the active resistance,thus maintaining the continuity of higher speed.3.In the upper stroke stage of the short-distance butterfly stroke,the first-level athletes have more precise cooperation opportunities,and the synchronization index T3 is closer to zero,which can fully superimpose the arm and leg propulsive actions,and improve the continuity of propulsive;The first level achieves higher hip joint acceleration through hip extension,and a slightly longer peak time difference between hip and knee acceleration,which accumulates potential energy,and cooperates with the trunk and arm during the stroke,making the ankle joint acceleration significantly higher than the second level.Although there is no difference in the proportion of time,the rhythm of the arm-leg cooperative force is significantly better than the second level,which improves the peak acceleration of the end joint,and can give full play to the combined force of the whole body,So as to greatly improve the promotion effect.4.In the air arm transfer stage of the short distance butterfly,the main difference between the first and second levels lies in the timing of arm and leg coordination.There is no significant difference between the synchronization index T4,the proportion of stroke time and the air arm transfer time between the first and second levels.However,the poor timing of the second level lift destroys the body streamline pattern,increases the active resistance,and ultimately reduces the continuity of speed. |
