In our modern world there are many activities we do that are hard on our bodies. A common activity for students is carrying backpacks. Backpacks present many of the problems that sitting and slouching does. The pectoral muscles are active and shortened to carry the backpack, and often the shoulders roll forward to place the pectorals into a stronger position. Frequently, the head comes forward as well to counterbalance the weight of the backpack. This position compresses the rib cage and limits lung capacity.
The weight of a backpack leverages against the back. This combines with the additional muscle force required to keep the body upright in this position and increases wear on the body. Muscle tightness with backpacks is especially prominent in the neck, upper back, shoulders, and chest, but extends throughout the rest of the back as well.
We often don’t feel the weight and strain backpacks place on our bodies at the time. Like with sitting and slouching, much of the weight and strain on the body when wearing backpack is placed on the ligaments. The muscles are like motors and take energy and effort to contract and function. The ligaments are like ropes, and are passive. Like bones, force can be placed on ligaments without requiring additional energy or effort, and thus it feels like it’s easier to lean on the bones and ligaments that it does to actively use the muscles to maintain a position. However, the ligaments are located at the joints, which are the leverage point of movement. This means that the ligaments can be under much more strain than the bones. Additionally, the ligaments are subject to hysteresis, where repeated loading and unloading cycles as well as constant prolonged strain can lead to the ligaments permanently stretching. These multiple factors combined can lead to ligament injuries.
Sometimes it can take years for symptoms to build up. This is especially the case for young and healthy people, such as children in school. Younger people typically have healthier ligaments as they have not had the time and years to build up wear. While ligaments stretch and weaken with prolonged stress, symptoms often occur suddenly. For instance, while you may have picked up and thrown on a heavy backpack, or bent down with a backpack on for years without problems, suddenly one day you may do this and have pain appear. This is especially problematic for children, as the weight of backpacks can result in postural changes as they are growing that can be difficult to overcome in later years.
Heavy backpack use can potentially damage soft tissues, including a group of nerves that comes out of the neck and upper back called the brachial plexus. This group of nerves provides sensory and motor function to the arms, and injury can produce symptoms including numbness and weakness in the arms and hands. The straps of a backpack press into the soft tissues at the upper back and anterior shoulders where the nerves of the brachial plexus pass. Over time and with enough force, this can injure these nerves. When severe, this can lead to a condition called backpack palsy or rucksack palsy.
Backpacks are especially problematic after injuries such as an auto accident. In an auto accident, multiple ligaments are injured throughout your body, but especially those in the neck and back. Due to injury, these ligaments are unable to properly manage shearing, or side-to-side translation forces placed on the spine. Leverage from backpacks further stretches and irritates already injured ligaments, aggravating pain, discomfort, and loss of function. Placing excessive shear force on the ligaments healing after an injury can lead to reinjury of the ligaments and prolong healing. Excessive joint slack from elongated ligaments that have not healed well increases wear on the joint and can lead to breakdown of joint cartilage and future arthritis.
Rolling bags and rolling backpacks avoid placing the weight of the bag on your body as well as avoid the leverage this would create. These bags require much less force and effort to move as the bulk of the weight is supported by the ground instead of your body.
Exercises can help manage and counteract some of the straining effects of backpack use. However, it is best to avoid this type of strain when possible, and rolling bags are a good option. Some postural exercises that can be helpful include Brugger’s stretches and wall angels.
Postural changes from backpack use that have become established can be difficult to change on your own despite improvements such as switching to a rolling bag and postural exercises. Your Chiropractor will be able to advise and instruct you on exercises and stretches that can help improve your posture as well as provide treatment for symptoms. Chiropractic manipulation can be very helpful to restore motion and realign joints that have become malpositioned with prolonged backpack use. Contact your Chiropractor if you are suffering from poor posture or symptoms associated with backpack use or an auto accident.