The Experimental Study On Technique And EMG Of Freestyle In Swimming Flume

Object：Taking the important of freestyle technique and EMG and the lack of reseachabout them to account, the aims of this study is to further study the characteristics offreestyle technique of national elite athletes and novice athletes; and in order tounderstand the condition of muscle activity during swimming in these athletes.Meanwhile, to master the training effect of the most advanced training and scientificresearch facilities in the wold—swimming flum; and also to investigate the trainningbasic of swimming flume for all kinds of althelets.In this study, surface EMG system synchronized with video cameras andswimming speed measurement systems were used to measure and analysis freestyletechnique and muscle activity of elite athletes and novice athletes in the swimmingflume, swimming pool and the stroke and EMG of activity muscles of these athletesduring training on swimming bench. The aims are to understand the characteristicsand discipline of stroke technique and muscles activity in different water speed ordifferent environment, and to understand the difference of the technique and musclesactivity in different training environment, and to provide a reliable foundation fordifferent levels of Freestyle swimmers to improvement and optimization theirtechnique, and provide a guide for the coach to draw up training program.Methods:Subject: twelve freestyle swimmers of xxx swimming team. They were dividedinto elite group and novice group according to their100m performance.Instrument: swimming flume, sEMG acquisition system,3-line swimming speedanalyzing system, swimming bench, underwater video camera, synchronized signal.Experimental program：The test was divided into testing in swimming flume, testingin swimming pool and testing on swimming bench. And it was divided into two parts when to carry out the test. The first test is in swimming flume and in swimming pool.The speed of testing was determined in1.20m/s, in1.40m/s and in1.55m/s. Thesecond test is on the swimming bench. The action frequency is the stroke frequency inswimming flume..The muscles: Ten muscles of left body side was selected in the first test. They are:1tibialis anterior,2gastrocnemius laterally,3rectus femoris,4biceps femoris,5latissimus dorsi,6pectoralis major,7biceps brachii,8triceps brachii,9flexor carpi,10extensor carpi. Six muscles of left body side was selected in the second test. Theyare:1latissimus dorsi,2pectoralis major,3biceps brachii,4triceps brachii,5flexorcarpi,6extensor carpi.Waterproof processing: The waterproofing material was used in the experimentto cover a10×12cm~2water-resisting layer on the surface electrode. The muscle ofgathering point and electrode were seal completely in the waterproof layer.Furthermore, the pre-amplifier was waterproof processing, and then put on the wholeswimming clothing.Results:(1) During test in swimming flume and swimming pool, the stoke frequency offreestyle of elite group and novice group show very significant differencesbetween1.20m/s and1.40m/s,1.20m/s and1.55m/s and show significantdifferences between the speed of1.40m/s and1.55m/s.(2) During test in swimming flume and swimming pool, the joint angular velocityof elbow, shoulder and knee in elite group was increases along with the speedincrease. In swimming flume testing, there are no significant differences ofshoulder extension, elbow flexion and extension among three speeds in elitegroup. There is a significant difference of knee extention between1.20m/s and1.55m/s in elite group. There is a significant difference of shoulder extension,elbow flexion, the second and the third knee extension between1.20m/s and1.55m/s. There is a significant difference of all joint anguiar velocity amongthree flows.(3) During test in swimming flume and swimming pool, the RMS of EMG in elitegroup was increases along with the speed increase. During swimming flumetesting, there is a extremely significantthe of RMS of all of testing muclsesbetween1.55and1.20m/s,1.40m/s respectively, and no significant differencebetween1.20m/s and1.40m/s is found.. However, there is a extremely significantof the of RMS of all of testing muclses between1.55and1.20m/s,1.40m/s respectively, and a significant sifference between1.20m/s and1.40m/s。Duringswimming poor testing, the RMS is a little small bigger than that testing in theswimming flume, but has no significant difference, and the statistical analysisof results and statistical analysis of flume test ing is consistent.(4) During test in swimming flume and swimming pool, the latissimus dorsi,pectoralis major, biceps brachii, triceps brachii and flexor carpi are highlyactivated during swimming in both elite group and novice group, they arechief muscles to produce the propelling forces, and the pectoralis major andbiceps brachii are highly actived in insweep phase, the latissimus dorsi andtriceps brachii are highly actived in outsweep phase, the flexor carpi is highlyactivated in both phases. However the contribution of the test muscles is quiteeven in the elite group, the latissimus dorsi is highly activated in novice group,the other muscles are smaller than elite group.(5) During test in swimming flume and swimming pool, a coactivatedphenomenon between biceps brachii and triceps brachii appeared in insweepand outsweep. However the coactivaed degree is increase along with theswimming speed increased in elite group, especially increases under1.55m/s.however it is decreased along with swimming speed increases in novice group.(6) During test in swimming bench, the joint anglar velocity and RMS of EMGare all smaller than which in swimming flume test. there is a extremelysignificant of the anglar velocity of shoulder extension, elbow flexion andextension between1.20m/s and1.55m/s. There is a extremely significant of the ofRMS of all of testing muclses between1.55and1.20m/s, and there issignificant difference between1.20m/sand1.40m/s, meanwhile, the coactivateddegree between biceps brachii and triceps brachii is decrease along with thestroke frequency increase.Conclusions:1This study is the first time of studying swimming technique with sEMG, theresult proved that the application of submarine EMG can carries on theeffective diagnosis to the swimming movement technology and the swimmingtraining.2The pectoralis major and biceps brachii are highly actived in insweep phase, thelatissimus dorsi and triceps brachii are highly actived in outsweep phase, theflexor carpi is highly activated in both phases. It can provide theoretical basisfor the special strength training. 3The swimming flume is a comprehensive platform for swimmers’ training, testand monitoring. It can adjust swimmers’ stroke frequency and stroke amplitudethrough change the water velocity. However it is not suitable to training eliteathlete in low speed flow, it would cause the technique changing and do notachieve the effect while athlete training in low flow. So it is recommended thatusing80%of best performance.of100m.4High elbow is one of technique of freestyle, Biceps brachii and triceps brachiiwill present EMG activity when conduct the high elbow. Calculating the degreeof coactivity between biceps brachii and triceps brachii can estimate the qualityof high elbow and stroke technique.5The swimming bench is a common special strength training instrument forfreestyle. However it must pay attention to the main point when use it, andcauses the training effect.