How Do You Injure Your Back at Work?
As a small-framed female chiropractor, I’m often asked, “do you injure yourself at work a lot?” Between the physical nature of my job and my size compared to many of the people I treat, I can understand why this question comes up so frequently. My chances of disability due to practicing chiropractic are quite remote, though. From the very beginning of my education, the importance of ergonomics in practice were infused into my methods, which, by the way, are different from those of my six-foot-four, 200 pound, male counterparts. This is not to say that I never hurt myself. There are times when I let down my focus and, if the conditions are right, might “tweak” a shoulder or wrist, just like any athlete would when caught off guard. However, the majority of damage I cause to my musculoskeletal structures comes about just like it does for anyone else – from the repetitive motion and chronic postures of computer-ing. I can’t imagine life without these useful machines but, as a chiropractor, it is imperative, for my own peace of mind, that I learn from these workstation mishaps, and use any insights gained to prevent such injuries in anyone who will listen. There are so many different ways to injure yourself while working on your computer, but, in this article, I will focus on those that occur in the low back with too much sitting and slouching.
Before starting into the mechanisms of these injuries and prevention, let’s look at some definitions and statistics. The general term for injuries that occur while serving some function to the world are termed “ergonomic” in nature. Ergonomics are literally the laws (normos) of work (ergos), and are defined as the science of adapting the job and/or equipment to the human for the purpose of maximal safety and productivity. Today, computer workstations are the major area of relevance for ergonomic applications, though the principles apply with equal importance to cars, cockpits and factories [1]. Humans were not designed to sit at a desk, hovering over a computer for hours at a time. For this reason, the workstation and behaviors must be adapted to fit the human if we are to prevent injury.
To get an idea of the impact these injuries have on the livelihood of our population, consider the following statistics taken from a report on Ergonomic Injuries in California by the US House of Representatives Committee for Government Reform in March, 2001 [2]. “Ergonomic injuries account for 1/3 of all occupational injuries and illnesses and constitute the single largest job-related injury and illness problem in the US.” “The National Academy of Sciences has estimated that the costs of ergonomic injuries to employees, employers and society as a whole can be conservatively estimated at $50 billion annually.” “Ergonomic injuries cost California’s economy over $4 billion each year.” Additionally, mechanical low back pain (that means back pain related to musculoskeletal injury, without any underlying disease) is the second most common symptom related reason for seeing a physician in the United States, and 85% of the population will experience at least one episode at some point during their lifetime [3]. This is not new information, and many employers are well aware of the benefits, from a business perspective, of providing furniture, computing tools, and employee programs that support good ergonomics. Even so, there are still many companies and individuals who have not yet been informed.
So, how do these injuries of the low back occur? In general, back injuries result from one or more excessive load(s) placed on the supporting structures of the spine. These include the vertebral joints – or facets, intervertebral discs - or discs, ligaments, the layers upon layers of muscles, and nerve roots (two at each vertebral level). The purpose of the spine is to provide stability for protection of the spinal cord, while allowing enough mobility for the moving around that is necessary for our continued survival. This trade-off for mobility compromises stability, which, while necessary, means there are inherent weak spots. Fortunately for us, we have nice big brains that are capable of learning how to outwit nature and make up for these slight imperfections.
With long periods of sitting, it is the discs that are most commonly compromised and, eventually, injured. Why? As the major shock absorbing structures of the spine, the fibers of the outer ring of the disc are subject to continuous stresses, which sometimes cause small tears to develop. If one of these tears is large enough, and the stresses inside the disc are strong enough, some of the inner nuclear material (the gel-like, shock absorbing substance located within the center of the disc) can leak through the tear. The disc is most vulnerable to injury postero-laterally, at the weakest parts of the outer ring, which also happens to be where nerves pass from the spinal canal and exit toward the legs (not the best design, in my opinion). If disc material compresses one of these nerves, there can be pain both in the back and down the leg, as well as deficits in neurological function [4]. Under a flexion load, the majority of the stress goes right to these postero-lateral weak spots. Flexion loads occur when we bend forward, lift something from the ground or a low shelf, or sit for long periods, especially if we sit without lumbar support. Rotation, or twisting, of the spine adds additional stress to the disc, such that turning to access file cabinets and/or pick things up further increases your chances of injuring a disc.
Slumped posture alone, though, over a long period of time, day after day, places tremendous stress on the disc. Furthermore, the constant strain that this chronic posture places on surrounding muscles and ligaments causes temporary deformity in the tissues, which lasts for a couple hours. As a result, instability in the region occurs for a time, forcing the disc to pick up the slack (remember, it’s the major shock absorber), and placing additional stress on it. This repetitive and sustained loading of the disc causes an accumulation of minor damage that, over the years, adds up. Finally, a single unguarded and seemingly innocuous movement, such as bending over to move a sprinkler in your yard, can result in sudden intense pain and disability; the type that lands some in the emergency room. Did I mention that painful spasms of the large back muscles accompany this type of damage to the underlying tissues? Both protective and painful, these muscle spasms are the most memorable part of throwing one’s back out.
Now that we know where things go wrong for the supporting structures of the spine, how can we prevent playing this scenario all the way through? First and foremost, we start paying attention to our postures and motions. All movement of the body is performed against a background of subtle postural adjustments. For this reason, good control of posture is important for spinal stability. Neutral posture is what you have when your spine has that nice S-shaped curve seen in all of the books and magazines. This is the posture that requires the least amount of energy for your body to maintain, and is also the position of which the least amount of strain is put into the supporting structures of the spine. The body is balanced and efficient when neutral posture is utilized, and, whether still or in motion, the supporting structures are afforded additional protection.
Next, we reinforce our stability. Remember? It’s a major function of your spine. The core muscles lie deep within the trunk of the body. They attach to the spine, pelvis and muscles that support the scapula, and stabilize these areas to create a firm foundation for coordinated movement of the legs and arms. The human spine was not intended to be the primary mover. That function was intended of the arms and legs. Every time we move, we depend on core muscles to hold us steady, and muscles of the arms and legs to actually move us. Core stabilization is the general term for how the muscles of your trunk keep your spine and body stable, which helps you stay balanced when you move. If your core muscles are strong and they contract when the arms and legs start initiate motion, your body is balanced and less likely to be injured.
The next issues are muscle flexibility and joint mobility. Short tight muscles perform less than optimally, add additional compressive load to the joints they surround, and decrease range of movement in the joints. Flexible muscles, on the other hand, allow reduced muscle tension, increased range of movement in the joints, enhanced muscular coordination, and increased circulation of the blood to various parts of the body. To maintain mobility and flexibility, muscles must be stretched and joints must be taken through their full range of motion daily.
The last component is activity and exercise. Aerobic activity builds stamina, which is important for maintaining postural control. It also promotes strength and flexibility, and supports a healthy circulatory system. Lastly, it stimulates and reinforces motor patterns. The complex neurological paths between the brain and moving body part involve an assembly of muscles, with subtle adjustments at the core and opposite side of the body to maintain balance, relaxation of antagonistic muscles to allow movement across the joint, and finally movement of all muscles along the kinetic chain to achieve a single action. Imagine how quickly this all must occur, one firing after another, to produce meaningful motion. Every one of the pathways involved becomes stronger, more hard-wired, each time a motion is performed, which is why attention to posture during activities is critical. Our brains remember the position of every joint involved during the motion and will replay it that way, unless there is conscious override. If we consistently perform sloppy and unfocused movements, which put stress into one or more of our tissues and/or joints, this will become our natural way of moving and will likely contribute to an overuse injury down the road. Conversely, the simple act of repeatedly focusing on how we move creates a subconscious ready position for the brain, such that unexpected external forces, like accidentally stepping off the side of the curb, will be easily compensated through motor coordination. Without this involuntary level of control, we might, instead, take a dive off the curb. I imagine that most people will prefer to stay on their feet if they can help it.
This is a lot of information to process, but it is fundamental to good musculoskeletal health and well being. Please refer back as often as you need. Now that you have this knowledge and the power that comes with it, please get back to work and save your back!
References:
1. Answers.com, Definition of Ergonomics, 07.22.09, www.answers.com/topic/ergonomics
2. Ergonomic Injuries in California, oversight.house.gov/documents/20040624115434-95141.pdf
3. eMedicine, emedicine.medscape.com/article/310353-overview, Mechanical Low Back Pain, 2006
4. Steadman, R., Lumbar Disc Herniation Overview. 2005, www.steadman-hawkins.com/spine_lumbarDisc/overview.asp
