CHAPTER 4 The Back and Why It Hurts CONTENTS 1 The Spine 2 The Back in Distress 3 Risk Factors 4 Lifting and Other Forceful Movements 5 Work Postures and Conditions 6 Tool Belts and Back Belts 7 Ergonomics and Other Safety Measures 50 INTRODUCTION The construction industry has the highest rate of back injuries of any indus- try except the transportation industry. Every year, these injuries causes 1 OBJECTIVES in 100 construction workers to miss anywhere from 7 to 30 days of work. Upon successful completion Most of the back problems occur in the lower back. There is a direct link of this chapter, the between injury claims for lower-back pain and physical activities such as participant should be lifting, bending, twisting, pushing, pulling, etc. Repeated back injuries can able to: cause permanent damage and end a career. Back pain can subside quickly, linger, or can reoccur at any time. The goal of this chapter is to expose risks 1. Identify the parts of the and to prevent back injuries. spinal column. 2. Explain the function of the parts of the spinal KEY TERMS column. compressive forces forces, such as gravity or the body’s own weight, 3. Define a slipped disc. that press the vertebrae together 4. Discuss risks of exposure disc tough, fibrous tissue with a jelly-like tissue center, separates the vertebrae to back injuries. horizontal distance how far out from the body an object is held 5. Select safe lifting procedures. spinal cord nerve tissue that extends from the base of the brain to the tailbone with branches that carry messages throughout the body vertebrae series of 33 cylindrical bones, stacked vertically together and separated by discs, that enclose the spinal cord to form the vertebral column or spine vertical distance starting and ending points of a lifting movement 51 1 The Spine Vertebrae The spine is what keeps the body upright. The spine’s basic functions include providing support to other body parts, protecting the spinal cord, and providing flexibility to allow bending and rotating. The spinal column, from the base of the skull to the end of the tailbone, is made up of 33 bones Discs called vertebrae. See Figure 1. The 33 vertebrae of the spine are divided into four sections, as shown in Figure 2. 1. The neck is composed of 7 vertebrae. The neck has quite a FIGURE 1 Vertebra and discs wide range of movement: up, down, and side to side. A broken neck occurs in this part of the spine. 2. The upper back is composed of 12 vertebrae. The upper back is much more rigid than the neck. It supports the upper body. 3. The lower back is composed of 5 vertebrae. The lower back supports most of the body weight. It has a good range of motion and bears most of the compressive forces. Compressive forces squeeze or press the spine together. 4. The tailbone is composed of 9 bones. In adults, these last bones of the spine have fused together to make the tailbone rigid. Neck Each vertebra is separated from the next by a disc. Discs are rings of tough fibrous tissue, or cartilage, with jelly-like center tissue. See Figure 3. Cartilage is the tissue at the ends of bones. It is capable of resisting a lot of pressure and reduces friction between bones. Compression of the spine can Upper Back damage the shock-absorbing discs between the vertebrae. A disc serves several important functions: ■ provides padding between vertebrae ■ acts like a shock absorber to protect the vertebrae Lower back ■ gives strength and flexibility to the spine ■ allows for movement between vertebrae ■ cushions the compressive forces that press the vertebrae Tailbone together Ligaments and muscles hold together the spinal column of vertebrae sepa- rated by discs. The spinal cord is made of nerve tissue and extends from the base of the brain to the tailbone with branches that carry messages throughout the body. See Figure 4. The spinal cord comes from the base of the brain and runs through the channel created by the vertebrae. Smaller FIGURE 2 nerves branch out between each vertebra to carry messages around the Four sections of the spine body. The spinal column ends at the tailbone. 52 Ergonomics Spinal cord Vertebra Vertabrae Nerve Disc Disc Muscle FIGURE 3 FIGURE 4 Disc function Spinal cord and nerves SELF CHECK 1. The spinal column is made up of bones, called vertebrae. 2 In adults, the last nine bones of the spine fuse together to form the . 3. act like shock absorbers to protect the vertebrae and give strength and flexibility to the spine. 4. The is made of nerve tissue and runs through the channel created by the vertebrae. When normally aligned, the spine forms 3 natural curves, sometimes called the S-curves. These occur at the neck (cervical), upper back (thoracic), and lower back (lumbar). Maintaining these natural curves keeps the spine in balance. Human bodies are designed to move, bend and flex. Body posture changes to fit the task. Static posture leads to discomfort and lower pro- ductivity. Just as there is a neutral position for wrists, keeping wrists straight and not THE BACK bent or twisted, so also the spine has a neutral posture. When in a neutral posture, the body will find its natural balance. Neutral postures include the following: ■ sitting posture ■ head balances naturally over shoulders instead of protrud- ing in front of body ■ shoulders relaxed rather than hunched up ■ forearms and thighs parallel the floor ■ body sits back in the chair for support, not on the front edge ■ chair back adjusted for support ■ feet set on the floor or footrest The Back and Why It Hurts 53 SAFETY TIP ■ standing posture ■ spinal column aligned in its natural S-curves Maintaining a neutral body ■ posture while working can help one foot propped on a stool to reduce stress in lower back prevent an injury. ■ change or shift posture often ■ stretch frequently throughout the day ■ body kept flexible, not rigid or fixed Maintaining the body in a static posture becomes uncomfortable and decreases productivity. Do not force the body to conform to its work- space. Adjust the work site to fit before beginning the task. Habitually poor posture will cause increased aches and pains. Feeling discomfort or pain is an indication that something is wrong. Heed the signs. Com- binations of awkward posture, force, repetitions, and insufficient rest periods are a set-up for injury. Combat this risk by taking more frequent “micro-breaks” before becoming fatigued. Also, become aware of mount- ing stresses, aches, and pains. 2 The Back in Distress The Center to Protect Workers’ Rights reports that 1 in 4 construc- tion injuries are back injuries, mostly from manual materials handling. According to the Bureau of Labor Statistics (BLS), back injuries account for 1 of every 5 injuries and illnesses in the workplace. Of these injuries, 80% occur to the lower back and are associated with manual materials handling. According to the BLS, the back was the body part most fre- quently affected by injuries involving days away from work in 2001. These injuries accounted for over 24% of the total 1,537,567 injuries in private industry. Re-aggravation of a previous injury almost always results from a new inci- dent, such as a slip, twist, trip, or extended reach. Lifting-related injuries include sprains, strains, and other injuries that can affect any part of the body, but the majority occur to the lower back. Most people will, at some time, feel muscle soreness and fatigue in the lower back. Often, it is impossible to pinpoint a specific cause. Back prob- lems that seem to “appear overnight” may have been building up slowly over a period of time. Sprains and Strains and Chronic Back Pain Ligaments attach one vertebra to another and help support the spine. A sprain is an injury or tear to a ligament. A strain occurs in muscles that have been stretched or used too much. Strained muscles and sprained ligaments both irritate the muscles around them. This adds to the pain and discomfort. When muscles, tendons, and ligaments in the lower back are stressed and stretched, a lot of chronic back pain can result. If exposed to risk factors 54 Ergonomics at work while experiencing chronic back pain, the body may not be able to recover. Pain, stiffness, and muscle weakness, even permanent damage, may result. Disc Disease The discs are the gel-like shock absorbers between the vertebrae of the spine. In degenerative disc disease, the discs break down. This usually happens in the lower back where the compressive forces are greatest. Over time, high stress on the back can cause tiny tears in the discs. If the stress continues, the gel gets pushed out of its regular position in the spinal column. This glob of disc gel then presses against one of the nerves that branch off from the spinal column. The nerves that branch off from the lower spine extend down the legs. That’s why pain from a “slipped” disc is often felt in the legs, below the pinch point. The symptoms of a pinched nerve include numbness, pain, and weakness. The symptoms are similar to those in the hand when the nerve in the wrist’s carpal tunnel is compressed. Degenerative disc disease develops slowly over time. A UBC member won’t know it is happening until the disc begins to shift. Repetitive awkward pos- tures and lifting, even light loads, can cause the problem. Slipped Disc A slipped disc is a disc that ruptures or bulges out of place.