The Red Viper vs. Mountain, sporting two different kinds of armor.

Medieval armor has a bad reputation when it comes to how much movement is possible for a fully-armored and outfitted knight. Chances are you’ve bought into the notion that it resulted in clunky, slow, and awkward battles.


Daniel Jaquet of the University of Geneva and several colleagues aim to bust that myth with a new study examining the range of motion and energy cost while fighting in medieval armor. They published their findings in a recent paper in Historical Methods: A Journal of Quantitative and Interdisciplinary History.

Medieval scholars have long known that armor worn by knights of that era allowed for far more mobility than most people realize. There’s even a 1924 educational film created by the Metropolitan Museum of New York to address the popular misconception. But until quite recently, little quantitative data was available to support that stance.


Jaquet et al. made their own educational video five years ago to highlight some preliminary findings of their research into this question:

This time around, the Swiss researchers recreated the training regimen of a famous French medieval knight named Jean le Maingre, a.k.a. Boucicaut, who racked up a number of military victories until he was captured by the English at the Battle of Agincourt in 1415. There is a written record of his training regimen, which included jumping onto a horse, running, swinging an ax or hammer, climbing a ladder from the underside using just his arms, and scaling walls—all while wearing his full-plated armor. Apparently few of his contemporaries could match him in sheer strength and stamina.

Jacquet and his colleagues had their test subject perform modern versions of Boucicaut’s regimen in comparable replica armor: jumping onto a pommel horse, running through town (to the delight of the locals), chopping wood, rock climbing, and performing the ladder climbing stunt. In the video below, the armor-wearing subject also demonstrates somersaults, cartwheels, flips, and even a bit of dancing:

That’s pretty convincing visual proof that medieval knights had a pretty impressive range of movement in their armor. But that doesn’t mean there isn’t a cost. There’s a reason Boucicaut had such a strict regimen: the extra weight of the armor means it takes a lot more energy to perform those biomechanical tasks.


While the Swiss team was conducting their experiments, British researchers led by Graham Askew of the University of Leeds were doing the same, culminating in a 2011 study on the energy expenditure of armored knights in action. The Leeds team recruited fight reinterpreters from the nearby Royal Armouries museum, and outfitted them in replica armor based on what was worn by a 15th century London Sheriff named William Martyn. Then the subjects hopped on treadmills while wearing respirometers to measure how much oxygen they used. From that, the scientists could calculate energy expenditure.

(Left) Fight interpreter on a treadmill wearing respirometry mask. Image: Graham Askew. (Right) Effigy of William Martyn (ca 1470-1480), whose armor served as the model for the replica used in this 2011 study. Image: Joy White.


The results: the volunteers used 1.9 times more energy while running and 2.3 times more energy while walking. “Some of it, I’m afraid, is really sort of stating the obvious,” Thom Richardson, keeper of armour at the Royal Armouries, told Popular Mechanics at the time. “It is harder to walk around wearing armor than if you’re not, but it is interesting to get figures for that.”

In particular, despite affording good protection and impressive mobility, it was the distribution of all that plated weight that was responsible for the increased energy expenditure—specifically on the arms, feet, and legs. The legs alone were carrying an extra 15 to 18 pounds, so the muscles had to work that much harder to overcome inertia to set the legs in motion. There is also evidence that the thin slits in the face mask, and tight chest plate, restricted oxygen flow even further.


The new study by the Swiss team reinforces those findings. So Boucicaut needed all that extra training to be the prime specimen of knighthood he was said to be.

Jacquet et al. insist their latest study is still just proof of concept, given that it featured a single test subject wearing one specific type of replica armor. They’d like to repeat the experiment with more subjects and different kinds of armor, to compile a more comprehensive data set. There is also the question of whether garments worn under the armor may further limit motion—perhaps even more than the armor itself.


That means we’ll likely have more fun videos ahead of re-enactors performing amusing stunts in full armor.

[Historical Methods: A Journal of Quantitative and Interdisciplinary History, via Medievalists.net]