Biomechanical Research To Double Leg Circles On The Pommel Horse

Objectives:The strategy of 2008 Beijing Olympics is approaching.As a traditional dominant sports event in China,the sport of gymnastics will be charged with an important mission.Little people has studied double leg circles(DLC) on the pommel horse from Biomechanics angle. This study investigates the dynamic mechanism and technique of DLC, which particularly uses the method of three-dimensional high-speed photography and film study,the method of surface electromyography (SEMG)and the computer emulation system based on dynamics of multi-body systems.The results could serve as effective training reference for gymnasts as well as coaches.Methods:1.Thirteen gymnasts are selected mainly from 2005,2007 gymnastics national championship.We use the methods of three-dimensional high-speed photography and film study to make technical analysis of DLC.2.The synchronous SEMG are tested while four gymnasts of Jiangsu province are performing DLC.The SEMG characteristics of the movement will be revealed.3.We use Lifemod to build a dynamic model of DLC for Chenchen.The results will be compared with that above. Results:1.During one circle of DLC,the time ratio of both-hand support phase (BHS) is about 17%while that of one-hand support phase(OHS) is about 33%.In general,the linear velocity of CM is minimal during BHS and maximal during OHS.However the linear velocity of foot was minimal during OHS and maximal during BHS.During the exercise,CM,each ankle and each shoulder should follow a nearly horizontal circular path.There should be an angle of about 180°at the hips.2.Of all The iEMG of the tested muscle,brachial triceps muscle is maximal,the cucullaris is minimal,latissimus dorsi and ectopectoralis are all above musculus obliquus externus abdominis,the left ectopectoralis is above the right one.3.For Chenchen,the results of the three methods support each other. During one circle of DLC,the force of brachial triceps muscle is the maximal,the time of ectopectoralis and musculus biceps brachii taking effect are all longer than others,left ectopectoralis works longer than the right one.Conclusions:1.It is suggested that gymnasts should have overtime during BHS.CM, each ankle and each shoulder should follow a nearly horizontal circular path.The height of CM should be as higher as better.There should be an angle of about 180°at the hips. 2.Brachial triceps muscle,deltoid,ectopectoralis,latissimus dorsi and musculus biceps brachii play an important role in DLC.They all show clear rhythmicity.Left ectopectoralis works much more than the right one.3.During DLC,latissimus dorsi is the main motion muscle.Musculus biceps brachii works with brachial triceps muscle to support the torso while ectopectoralis is fastening the torso.Deltoid fixes the shoulder joint.