Knights in shining armour: not so ideal?

20 July 2011

Suits of armour may have made medieval soldiers feel safe, but modern scientists have found that they were so heavy and constricting they were likely to have limited performance and even influenced the outcome of battles.

The research, by scientists at The University of Auckland, University of Leeds, and University of Milan, has been published in the Proceedings of the Royal Society of London, Biological Sciences.

“The steel plate armour worn by soldiers in medieval Europe weighed 30 to 50 kg, and there was a real trade-off between increased protection and reduced mobility,” says Dr Federico Formenti from the Department of Sport and Exercise Science at The University of Auckland.

“Our research showed that wearing a suit of armour doubled the amount of energy that a soldier used to walk or run, and substantially reduced their speed.”

For instance, a 38-year old man who could normally walk at up to 10 km/h would have been limited to 6 km/h in armour, while an older man of 55 years could only manage 5 km/h.

The effect was greater than could be accounted for by the extra weight alone, and reflected the distribution of armour around the body.

“Carrying a load of 30kg spread around the body requires more energy than carrying the same load in a backpack,” explains Dr Graham Askew from Leeds University. “This is because, in a suit of armour, the limbs are loaded with weight, which means it takes more effort to swing them with each stride. If you’re wearing a backpack, the weight is all in one place and swinging the limbs is easier.”

“In nature the fastest-running animals, such as cheetahs or ostriches, have relatively light and thin limbs,” says Dr Formenti. “Weighing down the limbs is clearly unhelpful in situations where quick movement is required.”

As if that wasn’t enough, suits of armour also appear to have constricted breathing. Armour limits the amount of air that can be taken in at each breath and increases the amount of energy required to breathe.

“Being wrapped up in a tight shell of thick steel makes one feel invincible but also unable to take a deep breath,” says Dr Formenti. “You feel breathless as soon as you move around in medieval armour, and this would most likely limit a soldiers’ ability to fight.”

The research was undertaken with a team of highly skilled volunteers accustomed to wearing armour for shows at the Royal Armouries Museum in Leeds. The amount of energy that the volunteers expended, while walking or running in exact replicas of four types of European armour, was calculated by measuring the amount of oxygen they used.

The results have implications for understanding the outcomes of historic battles. For instance the findings lends weight to the idea that exhaustion contributed to the defeat of heavily-armoured French soldiers against their lighter English enemy on the muddy battlefield at Agincourt (1415) and following the long march to the Battle of Crécy (1346).