My office is three miles from my house. If I walk at a slow, I-don't-want-to-go-to-this-meeting pace, I get to work in forty minutes. Same time for getting home. I did this for five years and I wasn't even in shape.
I'm not arguing that the Romans were slackers. Given the effort it takes to setup a Roman castra, the marching might be the least strenuous part of the soldier's day. Also, my daily walk is on paved sidewalk across mostly level ground, while the Romans often didn't have such advantages.
For an able bodied person walking through a shopping mall, three miles an hour is perfectly healthy and reasonable.
I'm not arguing that the Romans were slackers. Given the effort it takes to setup a Roman castra, the marching might be the least strenuous part of the soldier's day. Also, my daily walk is on paved sidewalk across mostly level ground, while the Romans often didn't have such advantages.
For an able bodied person walking through a shopping mall, three miles an hour is perfectly healthy and reasonable.