Am I more likely to hurt my back while lifting if the weight shifts or if it’s a sudden, unexpected load?

A recent study from the Netherlands reviews previous reports on back injuries from lifting unexpected weights. They go on to complete their own study of loads that shift during lifting.

So far, there’s no proof that lifting an unexpectedly heavy load is linked to back injuries. Lifting a load that shifts can increase the risk for injury. The reason for this is within the muscles, not the spine.

While lifting a load that shifts, the muscles may not respond quickly enough. This decreases the overall muscle force. But uneven muscle contraction (more muscle contraction on one side compared to the other) causes the vertebrae to rotate or twist. Rotation combined with increased pressure through the spine may injure ligaments or the disc.