In 1408, the anonymous book, “Livre des faits de Jean le Meingre, dit Boucicaut” spoke of knighthood, deeds, and the training of one of the most famous and successful knights in history, Jean le Meingre II. Among the training he did were mounting a horse without using the stirrups, climbing the underside of a ladder, chimneying up between two walls, running, chopping wood, and somersaults…. all while wearing a full suit of armor.
In 2016, Daniel Jaquet did some myth busting about the false narrative that knights couldn’t move well in armor. He used the early 15th century account as a basis for trying these things himself. In full armor. The full article he published is here but the following video of him doing many of these things is a great summary: