shoulder strap
A well-designed backpack, with thick shoulder straps and ventilating effect, will not feel uncomfortable when the general load does not exceed 1/3 of the body weight. Once adjusted, there won't be much space between the bag and your shoulder blades (except for people with hunched backs). A good bag can adjust the weight distribution on the shoulders at will, and you can adjust it at any time according to physical strength and environment.

chest strap
It is used to adjust the distance between the two shoulder straps. When using it, it should be adjusted so that the backpack can be close to the body without being oppressive. The chest strap is noticeable in reducing the weight-bearing effect of the shoulders.
backpack compression straps
The main function is to adjust the backpack capacity, external equipment and keep the center of gravity from moving.
  center of gravity adjustment belt
The connecting belt between the upper part of the strap and the backpack is the center of gravity adjustment belt, which is usually kept at a 45-degree angle. Tightening can move the center of gravity to the shoulders, loosening it can move the center of gravity to the hips, and by adjusting between the shoulders and hips, you can Reduce fatigue. On flat roads, you can adjust the center of gravity a little higher, and on the downhill, lower the center of gravity.