From The Bend Bulletin:

“Walking with a weighted backpack is called rucking. The activity has its origins in the military, where soldiers still use it to prepare for drills or combat roles. But some personal trainers say it can be useful for civilians, too — especially people who are preparing for a long backpacking or hunting trip or who need to take a break from running. They say the exercise builds muscle strength and burns more calories than regular walking, but there are important points to be aware of before setting out on your inaugural ruck up Pilot Butte.

…

Aside from being a relatively low-impact alternative to running, trainers say rucking provides a full-body workout and targets more muscle groups than walking alone.” 

Read more here.