Great strength was a requirement for all of the soldiers/warriors of this age not just those in armor. It is unlikely that today 1% of men could even draw an English longbow never mind shoot it from full draw hundreds of times in a battle. This strength made the difference between life and death in battle.

As a Marine, I did some of this stuff in modern armor and 782 gear. The weight is probably comparable. Different types of obstacle courses and very, very long marches with a ton of gear.