Patterns Of Electromyography Activity Of Trunk During Symmetric And Asymmetric Lifting And Lowering Task

ObjectiveStudy torso muscles electrical activity, center of pressure and change of trunk angle during the human body perform Symmetric and Asymmetric Lifting and Lowering task, revealing waist hip muscle activity and the center of pressure features and analysis torso motion control regular.Materials and MethodsStudy subjects:10healthy young male subjects. Laboratory equipment:Vicon3D trajectories of the infrared camera system, surface EMG instrument, KISTLER force platform. Perform two parts task(total of eight tasks):body before/behind Symmetric Lifting and Lowering(0kg,20kg); body before/behind Asymmetric Lifting and Lowering(0kg,20kg). Research parameters:EMG signal detection parameters:ten muscles’(erector spina, multifidus muscle,rectus abdominous,external oblique,gluteus medius,) AEMG.and percentage of muscle contribution, center of pressure (COP) in before-after (COPX) and left-right (COPY) direction of displacement curve; sagittal plane angle of trunk as the EMG activity staging reference.Each trial lasted4s, repeated three times, the obtained data do conventional statistical analysis and processing.Results:1、Symmetric lifting and lowering the object front of the body:Unload Situation,erector spinae and multifidus muscles in the torso movement between flexion and upright when activities (13.2%～37.1%), and abdominal muscles in the upright position with the extension bit between activities (5.8%～11%), gluteal muscle active low amplitude (4.7%～11.3%) in the four stages.Load Situation, back muscle activity increased (17.5%～56%), and have activities in four stages, the abdominal activity decreased (2.8%～6.2%), the gluteal muscle activities increase (9.1%～17.4%).2、Symmetric lifting and lowering the object behind of the body:Unload Situation, the abdominal muscles in the trunk movement to the upright position between the extension bit rectus abdominis (12.1%～19.9%) than the external oblique (7.5%～13.9%) significantly. Back muscles in the torso movement between flexion and upright when activities (13.2%～24.5%), the gluteal muscle activities in four stages have lower amplitude (3.8%～11.5%). Weight, increased abdominal muscle activity, the rectus abdominis increased more significantly (29.8%～38.9%). Back of four muscle activity in upright flexion increased (from15.2%～24.1%), the flexion back the upright stage, decline (12.1%～17.5%).3、Asymmetric lifting and lowering the object front of the body Unload Situation, the back muscles in flexion to the upright position and upright position to a period of flexion activities significantly (10.4%～31.7%), and abdominal muscles in the upright position to the extension bit and after stretching one-handed body premise put:activities significantly (8.2%～14.6%) is located to the upright position during the four periods of the gluteal muscle activity is consistent (5.9%～13%). Weight case, the back muscles activities in the four periods (10.4%～53.5%), and the performance of the left side of the erector spinae (16.5%～53.5%)(10.4%～30.9%) higher than the right side. The increase in the left side of the gluteal muscle (12.8%～23.3%), and little change in the right side.4、Asymmetric lifting and lowering the object behind of the body:Unload Situation, the back muscles in the upright position to flexion and flexion to the upright position during the activities significantly (10.4%～31.7%), abdominal extension position to the upright position in the post and upright with one hand and let the body:bit extension to the bit period activities significantly (from8.2%～14.6%), the gluteal muscle activities are basically the same four periods (5.7%～12.8%). Load case, the back muscles are still upright flexion and flexion position to the upright position during the activities is obvious, but the left (20.3%～27%), the right side is reduced (6.5%～11.2%). Abdominal muscles in four periods has increased, obviously the left (4.3%～47.1%) than the right (3.3%～19%).5、Performing four different mentioning place tasks, Unload Situation, the fore-aft displacement of the center of pressure variation89.3～103.1mm, left-right change is40.5～41.8mm; load case the fore-aft displacement of the center of pressure change110.6～115.1mm, left-right changes to40.5～53.9mm.Conclusion:Load and Unload task in the implementation of the uniform conditions, the size of the load is not the same position, neuromuscular control of the trunk will be different.1、Lifting and lowering the object front of the body task:back muscle activity increased significantly with weight increase, to a certain extent that the knee upright case and let go the objects easily lead to back muscle fatigue.2、During asymmetric lifting and lowering tasks,with weight increase, the active muscle at the same time increase the non-weight-bearing side increased significantly, the side of the antagonistic muscles increases, decreases on one side. Synergistic contraction of the external oblique against axial rotation of the more obvious.3、Gluteus medius dynamic task to maintain a certain activity rate, suggesting that the gluteus medius stable hip joint role in this process, to provide a basis for trunk flexion extension movement.