Armor reduces performance - its science

A study published July 19 in Proceedings of the Royal Society B shows that soldiers carrying armour in Medieval times would have been using more than twice the amount of energy had they not been wearing it. This is the first clear experimental evidence of the limitations of wearing Medieval armour on a soldier's performance.

 Heavy Metal Hardens Battle: Body Armor Hindered Medieval Warriors

This is a whole lot of armor.

This is not