Effects Of Different Support Stiffness And Intra-abdominal Pressure On The Function Of Abdominal Support

Objective: Low back pain is one of the main diseases affecting the quality of life of middle-aged and elderly people.It has the characteristics of high prevalence and high recurrence rate.One of the common causes is the lack of abdominal muscle strength.Novel abdominal support has been shown to reduce the activation of lumbar muscles and affect posture control in abdominal obese groups during exercise.The purpose of this study is to explore the influence of the changes of support stiffness and intra-abdominal pressure on abdominal support function,so as to provide an experimental research basis for optimizing the design of abdominal support and promoting the application of abdominal support.Methods: Eighteen subjects with insufficient abdominal muscle strength were recruited.Subjects were required to perform the task of lifting and lowering heavy objects.The root mean square amplitudes of thoracic erector spinalis,lumbar erector spinalis and lumbar multifidus muscles,the flexion range of motion of trunk and pelvis,and the plantar pressure center velocity were collected by the Noraxon Surface EMG Acquisition System,Qualysis motion capture system and Kistler three-dimensional force platform under the four support stiffness conditions(AT,PVC,PP,PVC-1)and two inhalation levels during wearing abdominal support(normal breath and deep breath).Subjects were asked to rate wearing comfort after each acquisition completed.The Surface Electromyography data were divided into four phases to deal with: from the standing posture to get the dumbbell tablet(phase1);return upright position with dumbbell tablet(phase 2);flexion the trunk to put it back on the stool(phase 3);then return to the start position(phase 4).Two-way repeated measures ANOVA are used to compare the effects of abdominal support stiffness and intra-abdominal pressure changes on human electromyography,kinematics and wearing comfort.All data were analyzed by SPSS 21.0 statistical analysis software,and the significance level was p < 0.05.Results:(1)Surface Electromyography: In the four stages,different support stiffness and inspiratory level had no significant interaction effect on the RMS of thoracic erector spinae muscle,lumbar erector spinae muscle and lumbar multifidus muscle(P > 0.05).Thoracic erector spinalis muscle: Wearing abdominal support under deep inhalation can significantly reduce the EMG activity of thoracic erector spinalis muscle(P = 0.038)in phase 3.AT support significantly increased the EMG activity of thoracic erector spinalis muscle than PVC support(P = 0.023)and PP support(P = 0.038)in phase 3.Lumbar erector spinalis muscle: Wearing abdominal support under deep inhalation can significantly reduce the EMG activity of lumbar erector spinalis muscle(P = 0.003)in the phase 3.In phase 1,AT support significantly increased the EMG activity of lumbar erector spinalis muscle than PVC support(P = 0.019)and PVC-1 support(P = 0.005).In phase 2,AT support significantly increased the EMG activity of lumbar erector spinalis muscle than PP support(P = 0.039),PVC support(P = 0.001)and PVC-1 support(P = 0.003).In phase 3,AT support significantly increased the EMG activity of lumbar erector spinalis muscle than PP support(P = 0.012),PVC support(P = 0.001)and PVC-1 support(P = 0.002);PVC support significantly decreased the EMG activity of lumbar erector spinalis muscle than PP support(P = 0.035)and PVC support(P = 0.015).In phase 4,AT support significantly increased the EMG activity of lumbar erector spinalis muscle than PVC support(P = 0.018)and PVC-1 support(P = 0.043).Lumbar multifidus muscle: In the four phases,the changes of support stiffness and inspiratory level had no significant effect on the lumbar multifidus muscle activity(P > 0.05).(2)Kinematics: Support stiffness and inspiratory level had no significant interaction effect on trunk and pelvic flexion range of motion and plantar pressure center velocity(P > 0.05).The pelvic flexion mobility during deep inhalation was significantly greater than that during calm inhalation(P < 0.001),but there was no significant effect on the trunk flexion mobility(P > 0.05).Compared with AT support(P = 0.018)and PVC-1 support(P = 0.003),PVC support significantly decreased the range of motion of trunk flexion.Compared with AT support,PVC support,PP support and PVC-1 support significantly increased pelvic flexion mobility(P < 0.001).PVC support significantly increased the medial-lateral velocity of plantar pressure center(P = 0.008)than AT support.The changes of support stiffness and inspiratory level had no significant effect on the anterior-posterior velocity of plantar pressure center(P > 0.05).(3)Comfort: Support stiffness and inspiratory level had no significant interaction effect on wearing comfort(P > 0.05).The four kinds of support stiffness had no significant effect on the wearing comfort(P > 0.05),The VAS score during calm inhalation was significantly lower than that during deep inhalation(P = 0.001).Conclusion: Increasing the stiffness of abdominal support can reduce the activation of back muscles.Although the increase of intra-abdominal pressure reduced the lumbar muscle activity during putting down heavy objects,it reduced the comfort of abdominal support.Increasing the support stiffness and intra-abdominal pressure can reduce the trunk flexion activity during flexion and extension,which is compensated by the increase of pelvic flexion activity.People with insufficient abdominal muscle strength can apply two support conditions to weight-bearing tasks according to the difficulty and complexity of tasks in life.