Do I have to carry a backpack on foot? Can't you carry a big bag?

You must carry a backpack when hiking. The shoulder strap with a large bag on the side will squeeze the chest, which is not conducive to breathing. Moreover, one shoulder is unevenly loaded and prone to fatigue. The stressed shoulder is constantly stressed and prone to soreness and numbness. There are many shortcomings in slung a large bag, so this method is not feasible. The use of shoulder bags can solve these disadvantages, so military backpacks are backpack-type.

As for short-distance movements, it doesn't matter what kind of bag you bring.