Anyone who regularly uses an over-the-shoulder bag should make sure that it weighs no more than five percent of the carrier's weight, says a leading German orthopaedist. Otherwise there's the risk of muscle pain on the side of the body where the shoulder bag is usually carried,
"Books in a shoulder bag are the curse of every orthopaedist," says Reinhard Schneiderhan, president of the German Spinal Association.
He notes that everyone has a side they favour when they carry a bag.
"The one-sided burden can lead to muscle tension," he says, noting special problems in the shoulder and neck on the carrying side, and the lower back on the other side.
Adhering to the 5-per-cent rule, he says people just carrying a phone and some keys can stick to over-the-shoulder bags. Anyone carrying more should consider a backpack.