Another medieval gear conundrum

[Rider of scaled wing]

I posted my first post like this in the workshop, and somehow i don't think it was really ment to be there, so this one goes out here.

There's an odd little fantasy idea that has warriors storing their shields on their backs when they're not in use, and reaching behind tehm and quickly pulling them off and into a ready position. Is this even realistically possible? I honestly don't see how it could really work, so if there's any experts on these forums, please step forward.

 

[The Ace]

Shields were often carried in this position over long distances, but carried in the hand or strapped to the arm if battle was likely. The Romans had a broad strap over the left shoulder and through the grip of the scutum, a narrower strap went around the wearer's chest and held the shield high, above the left shoulder. Modern experimentation has shown that, with the shield in this position, a practiced soldier can easily tug free the buckle and allow the shield to drop into the hand.

 

[Commonmind]

It's not very realistic to have them doing it quickly. Someone once asked me this same question while watching Troy, where during the beach invasion Achilles literally throws his shield onto his back. Look up shields in different time periods throughout history, the general makeup and constructions are similar throughout; I think you'll find your answer by doing some research. If you have plans to do this in a particular story, at least you'll have some reference for creating a realistic means of taking the shield on or off in hasty fashion.