|
Objective: Elastic band or tubing is widely used in athlete training,human exercise,patients and handicapped peoples in-homer ehabilitation and other fields.It is not only low cost,simplicity portability,versatility,but also can provid variable resistance without reliance on gravity comparing with other traditional sports equipment.Its,value has been proved by the foreign scholars.However,the reasearch of this field was rare in chhina,especially in its mechanical quantitative characteristics until this paper finished.For the value of its application,though some scholars are going to pay more attention on the value of its application,few publications could be found.In this paper,the author made some experimental studies in static and dynamic material properties of four different elastic bands and their training application value.The porpose of this study was to provide some references for readers and fill the domestic gap.Content:By use of barballs,millimeter scales,sony video camera,video analysis system,kistler force platform and so on,this paper researches and analysis the static and dynamic material properties of four different elastic bands and their applications to sports training. Researching variables include 1)static experiment:tension,deformation,strain percent,creep value,creep time,creep recovery value and time etc.2)dynamic experiment:tension,deformation rate,deformation acceleration etc.3)application experiment:motion cycle,velocity,acceleration in the whole motion time;max velocity,average velocity,acceleration,max angle,average angle,elongation,varying tension in flexion and extension time.Results:1)In static material mechanical properties experiment,the relationship between the tension and the deformation in blue and white elastic bands are non-linear when they are stretched within the threshold of 50% of their initial length,while linear when they are stretched beyond the threshold. However,to yellow and red elastic bands,the stretching threshold is 100% of their initial length.2)Static experiment results showed that different initial lengths of blue,white elastic rope tension - strain% curves do not coincide.10cm,20cm,30cm initial length curves show significant difference,while 40cm,50cm,60cm,70cm,80cm initial length curves are overlap. However,to yellow and red elastic bands,no matter how much of the initial lengths,their tension - strain% curves are full overlap with constant strain% .3) According to the specific initial length four different static elastic bands of tension - strain, tension - strain% curves,reached one linear regression equations over blue and white ropes stretching length of 50% initial length and yellow and red tubing stretching length of 100% initial length. The equations show the relationship between the deformation and the stress which could probably provide the basis of elastic bands static quantitative resistance.4) After 30 min with 5 kg loading, yellow contrast with red tubing ,the results indicate that their creep characteristics show significant difference(p<0.01),in this conditions,red tubing creep value is less than yellow.And after 15min unloading,the red recovery value is also less than yellow.5)Dynamic experiment show that under the 5kg,10kg,15kg loading,yellow elastic tubing time—deformation,time- tvelocity,time-acceleration curves is overlap,but red and white show differences with yellow tubing.6)Dynamic experiments of the four different types of elastic bands,the velocity of deformation curves show asymmetrical U-shaped according the time,at the curves beginning,they have a larger change value,when reaching max speed the change value will gradually decreas .The time from zero velocity to the max velocity is much shorter than from max speed to zero velocity.Under the same loading,the one with the much smaller elasticity has a long time to reach the max speed,a cycle of velocity is much longer,the max speed is smaller than the larger elasticity one.7)Dynamic experiments of the four different types of elastic bands,the acceleration of deformation show S-shaped with the opposite direction according the time.At the beginning ,the acceleration increasing then decreasing to zero,this is a threshold in direction.Then in the opposite direction gradually increasing ,decreasing to zero.The red one with a smaller loading will have a shorter time of this threshold.But white have a longer time compare with the red one.8 ) Under the 5kg , 10kg , 15kg loading,the yellow one deformation-tension curves coincide.But the red one no,it will have a shorter time to appear the max tension if the loading much smaller,and the deformation value is shorter than the yellow one.Compare with the red one,the white one under the 10kg,15kg loading appear max tension with different deformation value,but it correspond the time is shorter,the max tension is also smaller than them under the same condition.At the same loading,if the one with a much elasticity,it appear max tension at a shorter deformation,shorter time,and the max tension is smaller than the less elasticility one.9) Did the experiment of leg flexion-extension on standing position and thigh flexion-extension on prostration position by using 1m red elastic tubing.The result show that,after loading,the cycle of flexion,extension and the whole motion is longer than unloading.The extension cycle period reduce much amount than flexion cycle period.10)The results of leg flexion-extension on standing position by using red elastic tubing loading show that the max angle,max angle velocity,average angle velocity in the flexion and extension cycle period and the average angle velocity in the whole period were significantly increased.The extension scope is much full with loading.11)The results of leg flexion-extension on standing position by using red elastic tubing loading show that with loading the max velocity of flexion,the max and average velocity of extension have a slight decreasing compare with unloading.Average velocity during flexion time and the whole period have a slight increasing.During the extension period on prostration position,the max and average velocity all significant increasing,the max velocity,average velocity and the whole motion period average velocity is less but not significant.12)Compare standing position with supine position,the latter peak force is much larger.If use red elastic band to train leg force on standing position,during the extension period,antagonist muscles were extended much more completely.On standing period the whole cycle period,average velocity is larger than supine.But trainer can tie up elastic bands on their two legs to train force by turn to increase work efficiency. 13)Did flexion-extension motion on prostration position,the whole cycle period was shortage,average speed is increasing,especially in the period of flexion,the max speed and average speed increasing significantly.Conclusions : 1)In static material mechanical properties experiment conditions , the tension—deformation curves of the four different elastic bands does not fully conform to Hook Law (F=Kx).They have different linear thresholds.2) In static material mechanical properties experiment conditions,at the different initial lengths and the same stress,the percent of strain of the yellow and red tubes are a constant.3) In static material mechanical properties experiment conditions,we can use the linear part of strain—deformation value to gain regression equations,the eauqtions can describe strain and deformation accurately.4) Yellow and red tubes have different creep characteristics and recovery properties. 5) In dynamic material mechanical properties experiment conditions, at the specific download,they have the same deformations speed and deformations acceleration at the same time.6) In dynamic material mechanical properties experiment conditions, all of the yellow,red,white bands deformations speed and deformations acceleration have the change trend are first increase ,then decrease,but the thresholds are different.7) In the same dynamic material mechanical properties experiment conditions,the max srrain time of the white is earlier than yellow and red tube.8) In application of the experiments, compare with no loading , after loading the lower limbs maximum speed, the average speed, maximum angle, the average rate of the indicators reduced amount is not apparent, some indicators are even greater ,use the red elastic tube to training strength and speed training is practical.9)Compare the standing leg flexion-extension action with the supine position leg flexion-extension action ,the latter force peak is much bigger,but the former can make hip and leg extension muscles extension training fully.
|