Restrict The Movement Of The Lower Limb Flexion And Extension Movements Of The Trunk Flexibility And Bending At The Waist To Relax Characteristic

Background: With the rapid development of economy, people pressure gradually increasingin work and life. The pressure low back pain brings to the society is more and more prominent,such as the economic loss, medical burden and the Unemployment cause by low back pain.An epidemiological investigation shows, more than85%respondent had low back painhistory over their lifetime, which10%of people had to give up the original work because ofback pain. Although in our country, there were very few large-scale census about low backpain, and relevant statistics are lacking, but lumbar muscles strain is the recognised epidemicby the medical field in our country. The waist is located in the middle of the human body,because of the importance of its location, once its lesions occur will indeed affect the wholebody, affecting people’s normal work and life, so it got more attention in clinical andexperimental study. This study is to explore the working principle of low back of human bodyduring trunk flexion-extension process and the influence of the astrict of lower limbmovement and the flexion degree on low back by experimental methods.Research purposes:1) By measuring the body flexion-extension movements to know theregular of biomechanical indexes,such as the changes of flexion kinematics,the low backmuscles mechanics,dynamics during the process of trunk flexion-extension,so as to analyzethe kinematics characteristics of the low back part.2) Maintain the stability of the humanbody by securing lower limb during trunk flexion-extension,to observe the change ofmechanical index of low back part,and analysis of the principle of low back part.3) Bychanging the motion range of lumbar flexion during the test,to understand the influence of thechange of motion range on the EMG signal on and off of FRP （flexion-relaxationphenomenon）.4) to understand the working principle of low back part and the impact of thebiomechanical index on it,so that we can make a scientific explanation in mechanics field forthe various injury of the low back part from sports or working in our living,and providetheoretical basis for the treatment of lumbar injury.Methods:20Shandong Normal Universitystudents without low back pain nearly a year were selected in this study：10male subjects,average age is24.9±0.74,average height is176.7±5.01and average weight is68.9±6.49;10female subjects,average age is25.1±1.2,average height is165.7±5.87and average weight is56.1±6.98.Experimental instruments:Germany Biovision multi-channel surfaceelectromyograph,digital video camera,a light emitting diode,metronome,tape.Put on theprepared clothing,accurately stick the electrode and the mark points on the body ofsubjects,all the electrode through a wire is connected to the surface electromyograph,and detection if the connection is normal.The test action including free-standing mediumflexion-extension (FM) and deep flexion-extension(FD),lower limb secured mediumflexion-extension(SM) and deep flexion-extension(SD).Collect EMG datum,videos andflexibility datum,each of flexion-extension movements do three times.Comparison ofFM,FD,SM and SD test action,investigation during the process of trunk flexion andextension,the changes of EMG of erector spinae（ES）and biceps femoris muscle（H）and theirmutual coordination when the muscles are working; the changes of torque of upperbody;effects of lower limb movement restrictions on the changs of muscle work and torqueduring the flexion-extension,flexion degree.Mean data processing methods:Using Excel forstandardization of EMG signal and digital experimental video,and use SPSS11.5toanalyze,significant level is set to P=0.05Conclusion:1)The effects of lower limb movement restrictions on flexibility index mainlymake hip flexion angle decreases and waist flexion angle increases.Differences in flexibilityindex of male and female is hip flexion angle female’s is bigger than male’s and waist flexionangle male’s is bigger than female’s.2)The EMG signals of ES and H are all haveflexion-relaxation phenomenon(FRP),the flexion-relaxation time ES is longer than H,and thetime EMG turn off ES is earlier than H,the time EMG turn on ES is later than H.Lower limbmovement restrictions can reduce ES,H flexion-relaxation time,increase the degree of flexioncan prolong ES,H flexion-relaxation time.3)Flexion degree increasing and Lower limbmovement restrictions can increase ES EMG signal intensity.EMG signal intensity of ES andH in male than female,there was no significant difference in EMG signal intensity incomparison of male subjects and female subjects.4)Flexion degree increasing and Lower limbmovement restrictions have no significant on the torque of male when ES EMG off,but theycan make the torque of female increase when ES EMG off and the torque of male and femaledecrease when ES EMG on.The torque in male than female when ES EMG off and on.Therehas significant differences when ES EMG off.When ES EMG on,deep flexion has significantdifferences,medium flexion no significant difference.5)Flexion degree increasing and Lowerlimb movement restriction have no significant difference on the alpha angle and beta angle ofmale and female subjects when ES EMG on or off.Lower limb movement restriction andFlexion degree increasing can increase the alpha angle of male and female subjects when ESEMG on.