The first time we get the backpack, we first carry the backpack on our body and feel it, and then adjust the strap to a comfortable length. Bent over to jam the waist card, and try to tighten it as far as possible without affecting your breathing. Then shook the backpack upwards, tucked the shoulder straps back with both hands, not too tight, and finally straightened up.
The adjusted bag should have the bottom of the bag at the lower edge of the usual waistband, covering the small half of your buttocks. It feels like the bag is seated on your waist and hip, and the shoulder strap is mainly for stabilization, not the main stress point. Jump up and down, whether the center of gravity is swaying, whether the center of gravity is moving backward, if the rearward feeling is obvious, except for packing reasons, the adjustment belt between the upper part of the shoulder strap and the back of the bag may be too loose and tightened, generally at an angle of 45-60 degrees. Repeat this adjustment until there is no problem with backpacks.
