Carrying extra weight around can put a strain on the spine’s support mechanisms. This is especially true for the daypack or handbag that hangs limply over your shoulder for the bulk of your journey. The average commuter’s bag might weigh more than 15 pounds, and all of that weight puts an imbalance on both shoulders and back muscles. In order to help reduce the risk of back pain try keeping the weight of your bag or purse at less than 10% of your body weight.