It's historical facts, lol. Jean II Le Meingre aka Boucicaut, according to the chronicle "Acts of Marshal Busiko," he could climb a vertical ladder in full armor, using only arm strength, without the help of legs, and also do somersaults in full armament.
Not so much as you think possible. Experiments with modern accurate replicas of medieval combat armor showed a decrease in mobility of no more than 20%.
I personally saw with my own eyes how a man in full armor with plate gloves unscrewed the covers of soda bottles and played the guitar.