Load the ruck with something else. Concrete blocks are effective.
For those curious why - goes to only 1 in 100 having served in the military. Road marches with packs are the #1 option on the battlefield to get someplace, we don't have a motorcycle for every soldier in the force. You navigate cross country with 85 pounds of field gear and it's not a casual walk around the block.
For someone who's trying to keep up to combat reality, a ruck march is the preferred method. It's just going to look menacing to the public - they don't have a clue about what the job entails and can't see the point. I would pick what pack you choose with care, as anything military frightens the local fobbits. Even around Fayette.
Those who do hike - like, for days at a time, or even take the Appalachian Trail, it's a no brainer. Same as running a minimum of 6 miles daily and a marathon every weekend to run Boston.
At one time I was healthy enough to run the 12 mile EIB road march under the clock with the required ruck and rubber rifle. That was 32 years ago. Nobody thought much about practicing for it to stay in shape at 5k runs locally - but back then, 1 in 10 had served, so you got a wave every now and then, with a thumbs up.
Now? 8 shots to the face and a stern talking to? This isn't the country I planned to grow old in.