Many people carry their handbags, backpacks or laptop bags on one shoulder and they tend to have a favourite side to carry it on. Even if the bag is empty and light, the natural slope of the shoulder means that they have to elevate the shoulder blade to prevent the bag from sliding off. This constant contraction of the shoulder and neck muscles can cause overuse and pain. When the bag is full and heavy, the situation becomes much worse. This is because more muscles become involved and the strap can dig into the shoulder muscles causing irritation and cutting off local blood supply.
These overused muscles will become tense and cause pain in the upper back, shoulders and neck. This can sometimes lead to tension headaches and pain when turning the head.
To avoid these problems always try to evenly distribute the weight across both shoulders by wearing your handbag across the body or using both straps on a backpack. When shopping, spread the weight between two bags and carry one in each hand to even the load.
If you need any help or advice with your posture, please feel free to contact me.