Research Under Heavy Influence Of Mechanical Indexes Waist Trunk Extensors During Different Mention

Objective：Low back pain and the daily life has a very close relationship.Long-termrepeated excessive waist movement and overload,such as prolonged sitting, prolongedstanding or bent over position to the upright position from a hand-held weights canmake the lower lumbar erector spinae in a high state of tension,over time will leadlower back pain.In sport,especially in the large heavy strength training,compared withother athletes,the lower incidence of low back pain of weightlifting,athletics,gymnastics is higher. By using the surface electromyography,video and other systems,this article intends to provide a large range of load (0~30kg), study the human trunkflexion and extension movement,to explore flexion relaxation phenomenoncharacteristics, moment and other mechanical indicators during various load condions.Subjects：20graduate students (male) were selected from the Institute of PhysicalEducation, Shandong Normal University as subjects, subjects age25±0.82years,height176.4±4.1cm, weight65.9±4.9kg.20subjects were healthy, without lowerback pain and other back disorders.Methods：Using the German Biovision multi-channel surface EMG acquisition rightand left erector spinae,gluteus maximus,biceps femoris EMG signals,signalamplification1000,setting bandwidth frequency10-500Hz,1μV noise,CMRRis120dB,input impedance109K,the sampling frequency is1000Hz.Use digitalcameras (Sony-DCR-TRV17E) to acquire sports motion, the camera were placedthree meters away from the subjects,shooting frequency is50Hz;EMG and videosynchronization method,using an LED flashlight, lights on or off the LED flashlightwhen EMG signals is open or closed.Through different combinations of special box(5kg) and a dumbbell to configure seven different weight.Use JDP-2electronicmetronome (1time/second) to control the movement of the subjects rhythm, subjectswere asked to stand naturally, feet shoulder width, relax the body, at the startingposition the body is upright,eyes parallel with the horizon,double hands lift load(except0kg) to beat maximum bending from upringht(5s) and extension from themaximum bending back to the starting position(5s). Results：1) There are no significant difference between αmax and βmax underdifferent load(P>0.05).2) The torque of the L4-L5lumbar when erector spinae EMGon and off and the maximum torque value has an significant correlation (P<0.001)under different load.3)The flexion relaxation phenomenon parameter (inclinationangle of trunk and lumbar bending angle)under different load do not exist significantdifferences (P>0.05).4) under different load,the IEMG of the erector spinae,gluteusmaximus,biceps femoris between the two-stage of flexion and extension havestatistical significance;The τ values between0KG and5KG,10KG,15KG,20KG,25KG,30KG of erector spinae-gluteus maximus,erector spinae-biceps femoris,gluteusmaximus-biceps femoris have no significant difference (P>0.05) in the flexion phaseand stretch phase.5) With the increasing of load, at the beginning and the end ofmovement,the EMG amplitude is constantly increasing.In the phase of trunk flexionand extension, left and right erector spinae under different load showing a similarEMG;with the load increasing,left and right sides which share two triceps EMGamplitude has a tendency to increase and appear muscle discharge characteristics, theleft and right sides of the biceps femoris also show a similar flexion relaxationphenomenon,but as the load increases, the flexion relaxation phenomenon graduallydisappear and appear the increase of muscle discharge occurs burr disorderphenomena;compared with the erector spinae and the biceps femoris,gluteus maximusexhibit no similar flexion relaxation phenomenon.As the load increases, the right andleft gluteus maximus discharges also appeared irregular burr phenomena and muscledisorder.Conclusions：1)Various loads has no effect on the maximum inclination angle α andthe maximum lumbar flexion angle β.2) Based on the findings we can speculated thatthe torque when the erector spinae EMG on and off during trunk flexion andextension process possible is the maximum torque of the lower back.3) under differentload,the erector spinae EMG on and off corresponing inclination angle α and theflexion angle β are not affected. In load-sharing relationship, the increasing load onthe lower back make ligaments and other passive tissues on a higher tension that thelosing of the erector spinae work has not been compensated,which makes passive tissue in a very dangerous situation, Too large heavy load will lead to ligament (orpassive tissue) micro-damage.4) Different lifting load effect on the posterior part ofthe body muscle coordination mainly in:Along with the increase of load, on bothsides of the erector spinae,gluteus maximus,biceps femoris muscle EMG amplitudeappeared increasing trend;the IEMG of the erector spinae,gluteus maximus,bicepsfemoris between the flexion and extension have statistical significance duringdifferent loads;with different loads,the activity of the erector spinae-gluteusmaximus,gluteus maximus-biceps femoris muscle sequence patterns is fixed in theflexion and extension phase;under different loads,erector spinae-biceps femorismuscle electrical activity sequence has no fixed pattern.