Heavy Armor Gave Knights a Workout

Thursday, July 28th, 2011

It should come as no surprise that heavy armor gave knights a workout:

Researchers have found that the steel plate-mail armor worn during the 15th century, which weighed 30 to 50 kilograms, required its wearers to expend more than twice the usual amount of energy when they walked or ran.

Four historical interpreters at the Royal Armouries — who could perform cartwheels in the armor — ran on treadmills for the study, which monitored their oxygen consumption, heart and respiration rates, and stride length:

The interpreters expended about 2.3 times the amount of energy usually required to walk and 1.9 times the energy usually required to run while wearing armor than when they weren’t, the team reports today in the Proceedings of the Royal Society B. This energy expenditure is much greater than the energy that a person wearing a backpack of an equivalent weight would use.

The problem is the legs. The pseudo-knights wore heavy leg protection: cuisses on their thighs, greaves on their calves, and pointed shoes called sabatons on their feet. Together, these weighed 7 or 8 kilograms, Askew says, and having to swing that weight with each step really weighed them down. The farther the weight was from the center of the body, the more energetically expensive it was.

The researchers also measured the interpreters’ breathing patterns, which normally increase in both rate and volume when a person works out. But the volume of oxygen consumed by the armored runners stayed the same — presumably, Askew says, because the torso was compressed by a chest plate — so they were forced to take many rapid, shallow breaths.

Throughout history, soldiers have armored first their heads, then their torsos, then their arms, and then their legs, because armoring the arms and legs hurts mobility.

Doubling the energy expenditure from walking would roughly halve daily march distances, which would prove terribly limiting for foot soldiers.


  1. Ben says:

    The test was run using ceremonial armor. Combat armor for horsemen would weigh less. Foot soldier armor would weigh even less. The researchers should have contacted a historian, or even an SCA enthusiast, before running this test.

  2. Isegoria says:

    I didn’t see any reference to the armor being ceremonial, and it certainly doesn’t appear to be the extra-heavy specialized jousting armor that led to all the myths about medieval armor being so heavy that a knight needed a crane to climb into the saddle, etc.

  3. Goober says:

    The funny thing about medieval armor (or at least the armor shown here) was that to me at least, it seemed very overdone and not very effective. I’m not saying that I am an expert, but it seems to me that lamellar armor, the much lighter, cheaper, and more flexible armor favored in times past, fell out of style more than it fell out of usefulness. I think that a lot of medieval armor was all about bling — and the psychological aspect of going up against a steel-encrusted foe in battle.

    Not that the armor of the ancient Greeks was without criticism, but it seems to me that at least when it comes to the lamellar breastplates, they had the medieval folks beat.

    I am still of the opinion that the armaments of the Roman legions, with large interlocking shield walls, lamellar breastplates, metal shoulder and arm protection, helmet that protected the face and neck to a certain extent, javelins that could be thrown but not thrown back, and short swords made for thrusting up front, and long spears in the ranks behind, was pretty darned good for an infantry unit. The guys with the big, long medieval swords might have had an advantage in single combat, but the Romans didn’t typically fight in single combat. I would argue that a bunch of medieval knights fighting in their typical manner (in force but not necessarily as a unit) wouldn’t stand a chance against a Roman centurion and his men, even mounted.

  4. Isegoria says:

    I’m not sure why you would think late-medieval plate armor was overdone and ineffective. From what I’ve seen, it was less encumbering than earlier styles of armor, like chain mail, and offered better protection. Articulated plates allow more freedom of movement than flexible chain mail, and the weight is better distributed across the body; it doesn’t all hang off the shoulders and tightened belt. Also, I don’t believe that earlier forms of armor were necessarily lighter than late-medieval plate armor, unless we’re comparing a partial suit (like Roman lorica segmentata) to a full suit.

    I fully agree that medieval armor was meant to be impressive — but so was ancient Greek and Roman armor. Everyone likes shiny metal and tall plumed helmets.

    Lastly, the Romans did not have a great track record against cavalry, and they obviously had never had to deal with the shock of a lance charge from late-medieval heavy cavalry with stirrups. They had all kinds of strategic advantages — large numbers of professional troops, experienced generals and centurions, siege engineers, etc. — but their heavy infantry might find itself mauled by a first encounter with mounted knights.

  5. The Roman eunuch general Narses successfully cracked the code of beating calvary at the battle of Taginae against the Ostrogoths in July 552. It was forgotten in the West until the Scottish victory over the English at Stirling Bridge in 1297 and the Flemish victory over the French in the Battle of the Golden Spurs in 1302.

  6. Isegoria says:

    We haven’t had a good eunuch general in a while.

  7. Buckethead says:

    It’s not too late to start getting one ready.

  8. Must be a market incentive problem. We have plenty of eunuch politicians.

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