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I've been having some back pain that won't go away. I notice it seems worse after sitting for more than 30 minutes. Why would sitting cause it to hurt more? I would think taking the weight off my back by sitting would help, not hurt.

Many people with low back pain (LBP) report similar symptoms. Prolonged postures, especially sitting, increases the pain or discomfort. To find out why, scientists are using EMG studies to record the electrical activity of muscles in different positions. They are comparing the results from normal, healthy adults with no back pain to adults with chronic LBP.

So far they've discovered that the trunk and abdominal muscles should normally be in a relaxed phase during slumped or slouched sitting. When sitting upright on a stool with no back support, these same muscles are active and contracting to hold the posture.

People with chronic LBP don't seem to have a difference in muscle activity from one position to the next. They lack the relaxation phase. This altered pattern of motor control may be what sets them up for strain and pain. It's also possible that this impaired movement pattern started after the back pain came on.

Researchers will continue to try and sort this all out. EMG studies and real time ultrasound are very useful tools in measuring muscle activity. The goal is to develop a rehab program to normalize muscle activity.

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