| Objective: Lumbar are always under great gravity, also in daily life, we often are like turning, bending, stretching movements, adding to the lumbar(especially L4-L5) burden. Therefore, the waist is very prone to injury, disease. According to statistics, the incidence of low back pain in people over 40 years of age is higher than 60%, while the flexion relaxation phenomenon of the erector spinal muscle is often used as an evaluation of low back pain. Because of the low back pain and healthy compared to in the trunk forward flexion extension of the erector spinae muscle surface electromyography has significantly different, LBP paraspinal muscle flexion relaxation phenomenon is not obviously. Currently research on flexion relaxation phenomenon, mainly concentrated on the effects of weight and external load and body position on the, in the daily toil and movement, the muscle force improper or excessive fatigue and other factors will cause the waist injury. In this paper, we study the effect of the flexion relaxation of the vertical spinal muscle when the posterior muscle group of the thigh with the stability of the lumbar spine was in the state of fatigue,to provide a reference for further exploring the mechanism of low back pain, low back injury.Subiects: The selection of Physical Education College of Shandong Normal University(Changqing campus) 15(male) subjects, age 22 ± 1 years old, the height 180.3± 6.9cm weight 71.7 ± 11.4kg. The subjects were healthy, without disease and low back muscle fatigue condition.Methods: Thigh muscles before and after fatigue about erector spinae, around both sides of femoral biceps muscle EMG signals were collected by German biovision multichannel surface electromyography(EMG); of subjects of flexion and extension movements were filmed using digital camera(sony-dcr-trv17e); EMG signal and video synchronization method, using a shine a flashlight, flexion and extension movements begin and end, the synchronous light alloy closed shine a flashlight..Use JDP-2electronic metronome(1time/second) to control subjects at a uniform speed to do flexion and extension movement.Use the CON-TREX TP500 muscle test system made in Swiss to test the fatigue of the posterior femoral muscle group. Test of knee flexion by setting the mode of motion of passive- concentric contraction. First, the maximum peak torque of the muscle contraction of the posterior group was tested(the subjects performed a 3 passive- concentric contraction of angular velocity is 120 degrees /s,and take the maximum peak torque). Then, the subjects performed a certain time(time set of values greater than 30 minutes) of the knee joint passive- concentric contraction. When the peak torque is 30% smaller than the maximum peak torque of three times,so identified the posterior thigh muscle fatigue. Requirements: in the course of the experiment, the subjects crossed his arms across the chest, and the test process must be carried out with full strength.Results : 1)There was no significant change in the maximum inclination angle and maximum flexion angle of the trunk of the body before and after the fatigue of the right leg or left leg(P>0.05). 2) before and after the right leg muscle fatigue femoral biceps muscle in a frequency MF(median frequency) values were95.70±12.96、77.22±6.32; the left leg muscles before and after fatigue femoral biceps muscle bit frequency MF(median frequency) values were107.28±36.69 、 84.05±8.79. The results showed that there was a significant fatigue phenomenon in the posterior group of the leg,and no fatigue in the no test leg and vertical spinal muscle. 3) After the muscle fatigue of the right leg, the value of the turn off angle was 87.91±2.43、63.5±2.73, respectively. The value of the turn off angle was 51.65±4.26、36.46±5.41, respectively; after the muscle fatigue of the left leg, the value of the turn off angle was 90.76±3.33、73.02±4.07, respectively. The value of the turn off angle was 55.83±7.24、46.09±4.98, respectively. Experiments show that: in the left leg or right leg after the thigh muscle fatigue, the work time of the vertical spinal muscle becomes shorter, that is, the time of bending relaxation becomes longer.4) Femoral biceps and erector spinae muscle also bending relaxation phenomenon, but biceps muscle showed different EMG: some subjects left and right femoral biceps muscle appear bending relaxation phenomenon, some only unilateral leg bending relaxation phenomenon, some did not appear flexion relaxation phenomenon.Conclusions:1)There was a significant decrease in the MF of biceps femoris,and no significant difference in erector spinal muscle and non fatigue leg after fatigue test.2) There was no significant effect of fatigue on the maximum bending angle(trunk inclination angle and flexion angle) of the trunk of the left Hamstring Muscle or right Hanstring Muscle.3) When the left leg or right leg muscle fatigue, the EMG off time, the trunk inclination angleα and flexor lumbar angle β is small and there is very significant difference; the time of the vertical ridge muscle activity decreases, the time of bending relaxation increases. When the erector spinae stop working, for the completion of the bending action and maintain their weight torque and back non muscle tissues, such as lumbar fascia and ligament may share bear with much force, will increase the ligament injury risk. The incidence of low back pain may be increased if the exercise of the muscle fatigue in the posterior group is often associated with the bending.4)Left or right leg muscle fatigue has no produced significant influence on erector spinae and femoral biceps EMG and muscle coordination(correlation coefficient Rxy and phase difference τ). |
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