In a surprising study, researchers say regular lifting is not necessarily bad for your back, and they argue that not taking it so easy on the spine might help to ward off back pain.

Disc degeneration is one of the most common causes of low back pain, but little is known about why discs fail. One theory is that having a physically demanding job that requires regular lifting may be a primary risk factor.

An international team of researchers set out to test that theory by gathering information on 44 sets of male twins. They were identical twins, so they shared exactly the same genes, but they were included in the study because one weighed significantly more than the other, an average of 17 pounds more. 

Their theory was that, all genes being equal, having to carry around more body weight each day might damage spinal discs, which were measured by magnetic resonance imaging (MRI) scans.

What they found, however, was the opposite. The heavier twins had healthier spines, with about 6 percent higher bone density and less disc degeneration than their lighter sibling.

“Physical loading is beneficial for the muscular skeletal system. It’s good for bones, it’s good to make muscles and ligaments stronger,” says study author Tapio Videman, MD, PhD, a professor in the University of Alberta's Faculty of Rehabilitation Medicine in Edmonton, Canada.

Dr. Videman and his team say they hope their study results change the minds of people who think disc degeneration is caused by moderate lifting since they say they’ve discovered this type of routine activity actually does the opposite – slightly slows disc degeneration.

“If you have gradually increased your [lifting] levels, your body has probably adapted to those loads in a reasonable way and our findings don’t find that type of lifting or increased weight will increase disc degeneration,” explains Michele Crites Battié, PhD, another study author and professor in the University of Alberta's Faculty of Rehabilitation Medicine.

Battié says their findings only hold true with physical loading up to a certain limit. They say it is an entirely different situation when it comes to unusual or extreme heavy lifting.

“If you are not trained for a certain activity and you do something that is very demanding, that may have a very different effect,” Battié says. “I would guess that if your repetitions are too great and if the load is too great, there is likely a point when that becomes a negative thing for your skeletal system.”