Experimental Study On Evaluation Of The Function Of Lumbar Paraspinal And Glutenu Maximus By Surface Electromyography

Purpose: To study the function of lumber paraspinal muscle and Glutenu maximus by surface electromyography in the healthy subject with and without acute low back pain .Method: 7 healthy subjects without history of low back pain are recruited. All subjects performed a set of movement on Cybex 330: 1. Isometric contraction at different position (flexion 15,30,45,60,90 degree) with different effort (50%, 75% and 100% of maximal voluntary contraction). Every movement last 30 seconds followed by 60 seconds rest..2. Isokinetic contraction with different velocity (90 and 60 and 30 and 12 degree/s). 3. After 24 hour, low back pain (LBP) was induced by 1 ml subcutaneous injection of distilled water to the L4-L5 interspinous space 5 minutes prior to the measurement. Then the movements were repeated as what were did the day before.Torque was measured with Cybex 330. Surface EMG were taken with the electrode placed over glutenu maximus and the paraspinal muscles at L3L4 and L5S1 level.Result: 1.The MPF was influenced by n%MVC and angular velocity. The MPFslope wasn't influenced by n%MVC and flexion angle and angular velocity. The RMS is influenced by n%MVC. The flexion angle and angular velocity influence the RMS on different degree. 2.The MPF and MPFslope of L5S1 paraspinal are higher than that of L3L4 paraspinal. But the RMS of L5S1 paraspinal is lower than that of L3L4 paraspinal. 3. In isometric movement, theMPF of LBP is higher than those without LBP. The RMS is lower in LBP than without LBP. The RMS decreased only on L5S1 and glutenu maximus. In isokinetic movement, the increasing of MPF happened on lumber paraspinal and the decreasing of RMS happened on glutenu maximus only.Conclusion: 1. MPF and RMS are influenced by contraction strength and initial position of the muscle. 2. To subcutaneously inject 1 ml distilled water to interspinous is available for setting up the acute low back pain model. 3. In the early period of muscle contraction, the MPF of LBP is higher than that of normal and the RMS is lower. It may be the result that acute pain recruited fiber I more. 4. The function of glutenu maximus is important for low back extension.