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The Pressure of Handling Sudden, Heavy Loads

Nurses are at high risk for low back disorders because of handling patients. What happens when a nurse or nurse's assistant has to respond to a sudden load shift like a falling patient? Do the abdominal muscles all contract together at the same time? Ten well-trained judo and jujitsu fighters were put to the test to find out.

When the abdominal muscles contract, there is an increase in the pressure inside the abdomen. This is called intra-abdominal pressure (IAP). IAP helps stabilize the spine. It's an important part of protecting the spine when lifting or responding to sudden, heavy loads.

The 10 subjects were given various lifting trials with a healthy male acting as a patient. A device inside the abdomen recorded IAP during each movement. Muscle activity was measured on the outside using electromyography (EMG). A special computer program calculated the twisting (torque) and compression forces in the low back.

The results support the idea that IAP helps unload the spine by using an extensor torque. This is possible because one of the abdominal muscles, the rectus abdominis (RA), doesn't contract. The RA flexes the spine. If it contracted, it would be more difficult to handle a falling patient or heavy load.

The authors found that well-trained men and women don't make full use of the IAP when the trunk is exposed to sudden loads. Women have to use a higher IAP to handle the same load compared to men.

References: Morten Essendrop, PhD, and Bente Schibye, PhD. Intra-Abdominal Pressure and Activation of Abdominal Muscles in Highly Trained Participants During Sudden Heavy Trunk Loadings. In Spine. November 1, 2004. Vol. 29. No. 21. Pp. 2445-2451.

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