Narrator: This is Science Today. For the first time, researchers have been able to observe how discs in the back react to heavy lifting. Jeffrey Lotz of the University of California, San Francisco says they studied these effects by observing the tail of a mouse, which is actually quite similar to the discs of a human spine.
Lotz: There's a number of factors, not just loading, which cause a disc to degenerate and that's why it's been so complicated and so difficult to study. Even though it's been a problem for obviously a long time, there hasn't been a real definitive answer to why it happens. So this experimental model that we've developed is a way for us to try to separate one aspect of what might cause disc degeneration, which is physical activity.
Narrator: Lotz found if there's not enough recovery time after periods of heavy lifting, cell death occurs and alters the physiology of the disc.
Lotz: So ultimately we might be able to say that you need to have a certain amount of physical activity intermixed with certain periods of rest. Or inactivity in order to optimize your back - the biology of your back. And that's ultimately what we hope to try to define.
Narrator: For Science Today, I'm Larissa Branin.