Backpacks, tote bags, purses: all of them can cause strain if they're carried incorrectly. Sometimes, though, we have no choice about the things we have to take with us on our backs. In this case, how do you arrange heavy objects inside the backpack to do the least damage to your muscles? There are ways to place the objects inside so they collectively pose less of a problem.
First of all, it helps to look at the backpack itself. How is it designed, and how are the straps positioned? It's important to consider this before packing since it could affect how the weight feels and the way tension is distributed.
Next, you should try to limit the amount of weight in the pack if you can. Again, this isn't always negotiable, but if possible it should not exceed 15 percent of the weight of the person carrying the bag. Even then, the objects should be organized to minimize heaviness, in an orderly stack inside the pack to keep everything even.
The more consistently all the weight is distributed, the better you may feel, especially if you have to carry the backpack for a long time. Your goal is to stay as aligned and balanced as possible.
Finally, don't forget external factors. Your body strength will help make heavy backpacks less difficult, so work on developing your core if possible. There's also nothing wrong with using an alternative, such as a rolling suitcase, if the backpack is too painful.
Above all else, make sure you take recurring pain seriously. Visiting a professional chiropractor will give you the professional advice you need to plan ahead. An experienced doctor can let you know what behaviors will make your pain worse.