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. See Figure 5. The rupture frequently occurs during a slip, trip, fall or while lifting. But the underlying problem is usually that the disc has already been damaged by degenerative disc disease.

Spinal cord figure 5 Slipped disc THE BACK

Disc gel slipped and presses on nerve

Disc Nerves

Vertebrae

The Back and Why It Hurts 55 3 Risk Factors Back care is very important. Back pain is the largest cause of pain in the United States and the major reason people go to their doctors. According to the U.S. Public Health Service, one in five workers reported back pain last- ing at least a week. After experiencing a back problem, the chances of hav- ing it happen again are three times higher than someone who has never had a back problem. Using ergonomics and other techniques to prevent injuries are discussed elsewhere in Ergonomics.

The lower back takes most of the compressive forces, which act on the back during most of a person’s waking hours. Changing position from lying down to standing up doubles the compressive forces on the lower back! Sta- bility is provided by the two cords of back muscles on each side of the spine. They work as guy lines to keep the upper body centered above the hips. As a side note, medical studies have shown that without the support of back muscles, the spines of cadavers buckled under just 5 pounds of pressure.

Standing up is twice as stressful for the spine as lying down. But there’s more to life than sleeping. When standing, about 50 to 60 pounds of com- pressive force press on the spine. The force comes from the effects of gravity and the weight of the upper body. Standing most of the day compresses the spine about an inch. When sleeping, the pressure reduces and the com- pressed inch returns.

Some work activities can lead to back problems. Actions and activities that PRODUCTIVITY TIP can increase the risk of developing back problems are risk factors. Aware- Fewer injuries mean better ness of the risk factors helps to change some practices or equipment, reduces productivity and lower risks, and extends the ability to work and play free from pain. project costs.

Work-related risk factors include the following: ■ lifting and forceful movements ■ bending, twisting, and unequal lifting ■ repetitive movements ■ work postures ■ workplace conditions ■ strength, size and fitness ■ tool belts and back belts

Notice that forceful movements, static work postures, repetitive work, and poor workplace conditions are also risk factors for CTDs of the upper extremities. “I’m 39 years old, and I’ve had both knees operated on, both hands, and severe back pain. I’ve seen a lot of jobs with a fork- lift or crane sitting right there, and the old timers will want you to lift something by hand.” B. G., 39 years old, 20 years as pile driver, carpenter, millwright

56 Ergonomics SELF CHECK

1. is the effect of gravity on the body. . 2 When normally aligned, the spine forms 3 natural -curves. 3. When seated, keep forearms and thighs to the floor.

4 Lifting and Other Forceful Movements Lifting is a forceful movement requiring energy and muscle effort. It stresses muscles, tendons, and ligaments and increases the compressive forces on the spine. This is true even when a UBC member is lifting properly. Bend- ing from the waist at the same time as lifting an object increases compres- sive forces on the spine even more. See Figure 6. This is also true when reaching, twisting, or holding the object away from the body while lifting. One arm lifting or lifting and carrying using one shoulder or one hip also places extra and uneven stress on the spine. PRODUCTIVITY TIP The load on the spine is a combination of the weight of the object being Have materials delivered close lifted and the weight of the upper body. About 70 percent of body weight to where they will be used to is in the upper body. Bending over from the waist instead of lifting with a minimize manual material handling and save time. straight back adds the weight of the upper body to the lift, along with the object being lifted.

figure 6 Working bent over THE BACK

The Back and Why It Hurts 57 Factors Affecting the Stress of Lifting Back injuries from overexertion are rarely the result of a single event or accident. In some cases, an accident may have resulted in a pulled muscle. But the muscle really didn’t become bothersome until after several weeks or months of repetitive lifting or awkward work postures. In other cases, months or years of repetitive lifting, pushing, pulling, and carrying didn’t become noticeable until a single lift produced significant pain from a bulg- ing or ruptured disc. See Figure 7. Several factors could influence stress from lifting: ■ the weight, shape, and size of the object ■ horizontal distance, how far away from the body the object is held with the arms extended ■ vertical distance, where the lift starts and where it ends ■ lifting and twisting or bending at the same time ■ how much lifting is performed

Heavy objects require more energy to lift than lighter ones. However, the shape of the object greatly influences how difficult it will be to lift. For example, a box of nails weighs more than a bundle of insulation. The com- pact size of the box makes it easier to lift and carry. A squat lift can be used (bent legs, straight back). The box fits between the knees and can be held close to the body. Because of the shape, the insulation is large, cumbersome, difficult to grasp and because it itches, it is not pleasant to hold close to the body.

Lifting an object that has to be held away from the body (horizontal dis- tance) can increase the compressive forces on the back substantially. If the object is too big or bulky, the squat lift won’t work. The stress on the lower back increases by three times when bending from the waist to lift an object compared to lifting with a straight back.

figure 7 Spinal cord Bulging/ruptured disc

Disc gel slipped and presses on nerve

Disc Nerves

Vertebrae

58 Ergonomics The lower back is especially susceptible to injury due to the mechanics of the human body and the type of tissue and structures that make up the spine. The upper body can be thought of as a lever arm and the low back as the fulcrum, or pivot, point around which the trunk rotates. See Figure 8. For this reason, the compressive forces on the spine are the greatest at the fulcrum point and consequently can cause the most damage to the discs that sit between each vertebra.

For instance, lifting a 20-pound bag of flour 20˝ away from the body pro- duces approximately 400 pounds. of compressive force on the discs at the fulcrum point. This is 20 times the weight of the actual object lifted! In this example, it is not only the distance of the sack of flour from the body that contributes to the large compressive force, but also the weight of the body’s trunk as it bends forward. The muscles in the back have to work to support the weight of both the flour sack and the upper body. For this reason, even if a person is not lifting an object, large compressive forces are produced just to maintain the trunk in a forward bent posture.

Try to keep the vertical distance of lifts between knuckle and shoulder height. See Figure 9. The lift should not start below knuckle height nor end above shoulder height. Lifting from below knuckle height puts stress on the legs and knees as well as on the back. Lifting above shoulder height puts stress on the upper back, shoulders, and arms.

figure 8 Upper body mechanics

400 lbs of compressive force 20 lbs THE BACK

Fulcrum

20 in lever arm 2 in

Resistance arm (distance from back muscles to fulcrum)

The Back and Why It Hurts 59 figure 9 Storing lumber

SAFETY TIP Frequent lifting of even light loads can cause localized muscle fatigue or whole body fatigue. Fatigue increases the risk of accident and injury. Store materials so the verti- Frequent lifting also puts stress on the discs, tendons, and ligaments of cal distance of lifts is between knuckle and shoulder height. the back.

Other Forceful Movements Pushing, pulling, tugging, and sliding objects are examples of other force- ful movements. These movements require a lot of effort. They put strain on the lower back. They also stress the muscles, tendons and joints of the shoulders, arms, upper back and legs. How much force these movements require depends on the amount of force used to pull or push the object. Pulling, which stresses shoulders and arms, is worse than pushing. Pushing allows the use of the entire body weight.

Body posture while pushing or pulling is also a factor. In an awkward pos- ture, more force must be exerted to move the object. Friction between an object and the surface also requires more force to move the object. Using a screw gun or pneumatic nailer are examples of pushing. Stress on the back can be reduced by supporting the upper body with your other hand as shown in Figure 10.

Pushing or pulling an object above shoulder height or below waist height is very stressful on the body. The awkward posture requires more force. See Figure 11. The problems encountered by the upper extremities are also transferred to the back. Lifting an object vertically is difficult because it’s

figure 10 Supported upper body

60 Ergonomics figure 11 figure 12 Pushing above Arching backward shoulder height

moving against gravity. Objects that shift or fall cause the body to jerk, and in response to the sudden change in weight and resistance, that movement can cause injury.

Bending sideways or twisting the trunk also puts stress on the lower back. PRODUCTIVITY TIP Reaching backward usually causes the back to arch. See Figure 12. This Using mechanical means, increases the amount of force on the lower spine. It also puts stress on the such as a forklift or board upper back, shoulders, and arms. Avoiding these awkward body positions cart, reduces the material may be as simple as moving the ladder, working surface, or repositioning handling done and increases your body. productivity.

Forward reaches that are longer than arm’s length and require bending or stretching put stress on both lower back and legs. See Figure 13. Applying force with arms out in front of the body increases the stress on the lower back. An example is reaching forward while using a portable power saw. One way to reduce the stress is to support the upper body with one hand. Avoid bending the wrist backwards. THE BACK

figure 13 Reaching forward

The Back and Why It Hurts 61 Carrying an object using only one shoulder, arm, hand, or hip puts unequal stress on the spine. See Figure 14. The more reaching, twisting, sideways bending, and unequal lifting or carrying a UBC member does, the greater the risk of back injury. Alternating the load between shoul- ders or dividing the load for a two-arm carry is better for the body. Even simply balancing the load reduces stress.

The more a UBC member is required to bend, lift, twist, or reach, the greater the chances of developing back prob- lems. It is like the tires on a car—the more driving done, the faster the tires wear out. Repeated stresses on the back can also speed up normal wear and tear.

figure 14 Carrying lumber on SELF CHECK one shoulder 1. Standing up is as stressful for the spine as lying down. . 2 How far away from the body the object is held is the distance. 3. Keep the distance of lifts between knuckle and shoulder height.

5 Work Postures and Conditions If much of the daily work involves bending over, leaning forward, and working with the arms above shoulder height, it is likely that the body may be in one posture for long periods of time. These postures put stress on the lower back and shoulders. Static work activities are extremely tiring. See Figure 15. When one posture is maintained without moving or chang- ing position, muscles remain contracted. Blood flow to the contracted mus- cles is reduced; so muscles tire quickly.

For the UBC member currently experiencing low back pain, constant standing can be very painful. Putting inserts in boots and standing on pad- ding rather than hard ground or concrete may help. It is important to move around, change positions, and rest muscles as often as possible.

When the weather is hot, fatigue can set in quickly. Heavy physical work raises body temperature, making the UBC member feel even hotter. Work- ing in hot environments can lead to carelessness, lack of concentration, dehydration, heat exhaustion, and, in extreme cases, heat stroke.

Cold can also increase the risk of muscle strain. During cold weather, muscles tend to tense, which makes strains more likely. On the other hand

62 Ergonomics figure 15 Static work activities

when it is cold, heavy physical work helps to warm the muscles. Fatigue is less of a problem in cold weather.

Mud, wet, oily floor surfaces and poor housekeeping are serious slip-or-trip hazards. See Figure 16. Materials, wires, power cords, and tools on the ground are also common causes of slips and trips, which in turn can cause back injuries. The sudden stop either from a fall or as bal- ance is regained can whip the back out of alignment and cause damage.

figure 16 Poor housekeeping THE BACK

The Back and Why It Hurts 63 figure 17 Reaching over an object

Reaching over, under, or around an object or barrier increases the stress on the lower back. See Figure 17.

6 Tool Belts and Back Belts Wearing a tool belt, which can weigh anywhere from 25 to 60 pounds, puts stress on the lower back and hips. See Figure 18. Adding suspenders

figure 18 Wearing a tool belt

64 Ergonomics to the tool belt can help redistribute the weight, but it requires adjustment until the shoulder-waist-hip distribution best suits the individual. Other- wise, suspenders can also cause shoulder discomfort. The best strategy is to reduce the weight of the tool belt. If it’s not needed, don’t carry it.

Using a back belt to prevent injuries does not fall within recommendations by the National Institute for Occupational Safety and Health (NIOSH). The Institute concluded that, although back belts are being bought and sold under the premise that they reduce the risk of back injury, insufficient scientific evidence has been accumulated that they actually deliver what is promised.

Wearing a back belt increases pressure in the abdomen. See Figure 19. In the past, it was thought that this increased pressure made it easier for back muscles to lift a given weight. Evidence shows that increased abdominal pressure does not help back muscles in this way. One study found that back belts raise blood pressure and may present a problem to wearers who suffer from high blood pressure or other cardiovascular problems.

There is evidence that the risk of back injury actually increases when UBC members, accustomed to wearing back belts, stop using them. Wearing back belts for a period of time can cause the muscles of the trunk to weaken. Weakened muscles contribute to increased risk of back injury. Back belts

figure 19 Wearing a back belt THE BACK

The Back and Why It Hurts 65 also give a false sense of security. Lifting heavier loads may be attempted. Thinking that the belt will support the back, warning signs of pain or dis- comfort may be ignored.

7 Ergonomics and Other Safety Measures Size, Strength, Fitness Bigger isn’t always better. The advantage or disadvantage of size depends more on the work and workplace conditions and layout than on a UBC member’s physical size. If the work area is not designed so that both tall and short people can work comfortably, then both may need to bend over or stretch to do certain jobs. For example, a tall person may need to bend to reach materials stored for an average person at waist height or lower. A shorter person may need to reach overhead to do certain work. In either case, the stress on the lower spine and muscles increases.

Regular exercise that strengthens both back and abdominal muscles can help reduce back pain and discomfort. Being fit helps the heart pump more efficiently. People who regularly exercise aerobically can usually improve the efficiency with which their bodies use oxygen and the capacity of their cardiovascular systems to deal with vigorous exercise or work. A fit person that does not get winded as easily as a less fit person, and an aerobically fit person whose muscles are in good condition will be less fatigued at the end of the workday. However, everyone has limits. Working beyond those lim- its, no matter how fit, will result in fatigue and possible injury.

Apprentices are assigned some of the hardest work. Being young and strong, they sometimes carry more weight than they should. Apprentices should be protected against back injuries, so they can eliminate back inju- ries . Working safely means using common sense in the workplace, staying physically fit, and making injury prevention a top priority. Apprentices as well as all UBC members need to taught ergonomics and other safety precautions.

Strong leg, arm, and back muscles make it easier to lift or hold heavy objects. Muscle strain is decreased by being in good condition and warm- ing-up muscles before starting work is also recommended. Warm-up exercises bring blood to muscles. Attempting lifts beyond physical limits or capacity increases the risk of injury. Lifting affects the discs no mat- ter how fit or strong a person is. Each lift adds to the compression forces on the discs. Repeated bending, twisting, and lifting, especially of heavy loads, can cause tiny tears in the discs. Over time this cumulative damage may result in a ruptured, either herniated or slipped, disc.

66 Ergonomics Lift Techniques

Most people have been taught that the proper lift technique is the squat lift, SAFETY TIP with knees bent and back straight. In fact, the proper lift depends more on the size and shape of the object being lifted than on any set technique. Avoid lifting loads weighing more than one third to one half It may not be possible to hold big or bulky item against the body while of your body weight. lifting. Holding an object away from the body increases the compression on the spine. Compression on the spine happens no matter what lift tech- nique used. Some think holding your breath while lifing is good. Holding the breath means that the muscles are not getting the energy and nutrient needed to work.

Lifting involves many different muscles. Most lifts from the ground to waist level use muscles from the leg and thigh. Lifts between waist and shoulder use the back muscles. Lifting above shoulder height uses muscles from the upper back and shoulder.

A squat lift puts stress on the leg and thigh. It also requires a lot of energy from the leg muscles. Most freestyle lift rather than squat lift. Freestyle lift- ing is where the legs are almost straight and the back bent. Freestyle lifting puts more stress on the back but requires less energy than squat lifting. See Figure 20.

Things UBC members should avoid doing: figure 20 ■ lifting from the floor Lifting a box correctly ■ twisting with the lift and incorrectly ■ lifting with one hand ■ lifting loads across obstacles ■ lifting while reaching or stretching ■ lifting from an uncomfortable posture ■ trying to recover a dropped object ■ holding the breath while lifting

Guidelines to follow when lifting include: ■ planting feet firmly, with one foot slightly in front of the other, to get a stable base Correct THE BACK ■ bending the knees, not the waist ■ tightening abdominal muscles to support the spine ■ getting a good grip by using both hands ■ keeping the load close to the body ■ using leg muscles while lifting ■ keeping the back upright and in its natural posture ■ lifting steadily and smoothly without jerking ■ breathing

It is important to be careful about the way items are lifted. The best way to prevent back problems is to eliminate or reduce the need for heavy lifting. Incorrect

The Back and Why It Hurts 67 Summary The construction industry has been identified as having an exces- sive number of back pain sufferers because of the heavy physical demands required to complete many tasks. Lower back pain is the most common reason in the industry for missed work. Worksite conditions, work practices, exposure to risks, and job tasks all contribute to injuries. Because the work day is only one-third of the total day, UBC members should plan tasks carefully to avoid a painful back injury so the remaining two-thirds of the day can be enjoyed. Ergonomics and other safety measures can help UBC members avoid back injuries.

68 Ergonomics chapter Review

The Back and Why It Hurts questions

Show an understanding of the information in this chapter by answering the questions and filling in the blanks below. 1. The five vertebrae of the lower back support most of our body weight. (True; False) 2. Bending from the waist to lift an object puts three times more stress on the back than lifting with a straight back. (True; False) 3. The stronger and fit a person is, the less lifting affects the discs in the back. (True; False) 4. Damage to the spine can occur when the body lifts and twists at the same time. (True; False) 5. Carrying a load on one shoulder may reduce pressure on the spine. (True; False) 6. Muscle fatigue tends to set in more quickly in cold weather. (True; False) 7. When lifting an object, it is better to keep the object close to the body. (True; False) 8. Holding an object at arm’s length as opposed to waist-high and close to the body doubles the stress on the back. (True; False) 9. Changing body position often is one way to reduce the stress caused by awkward and static postures. (True; False) 10. Lifting materials with arms fully extended in front of the body is a risk factor for lower back problems. (True; False) 11. Most back injuries occur in the . 12. separate the vertebrae in the spinal column. THE BACK 13. The part of the spinal column that is fused together is called the . 14. A(n) is tissue that has ruptured or that bulges out of place.

15. Because they are usually young and strong, how often should apprentices carry loads? a. always b. when the loads are safely balanced c. never d. only in the morning

The Back and Why It Hurts 69 16. If working below knee level for long periods of time, which of the following would help reduce stress on the body? a. kneeling all the time b. bending at the waist all the time c. squatting all the time d. changing position often and taking micro-breaks 17. Which type of lifting is better for the back? a. twisting b. reaching c. bending d. squatting 18. What part of the spinal column is most susceptible to injury? a. discs b. spinal cord c. vertebrae d. nerves 19. Why is lifting a large bulky object riskier than lifting a compact one of equal weight? a. A bulky object has a lower center of gravity. b. A bulky object may fall apart easily. c. Bulky objects must be held further from the body than compact ones. d. Bulky objects force the UBC member into a bent back position. 20. Why is pushing an object safer than pulling an object? a. Pushing lets the UBC member use body weight to best advantage. b. Pulling can weaken the blood vessels in the arms. c. Pulling causes very serious knee problems. d. Pushing allows the use of the powerful muscles in the hands and fingers.

70 Ergonomics worksheet 1 Small Group Activity

Instructions Work in groups to complete the demonstration and answer the questions.

Activity description ■ Use proper lifting techniques.

Materials ■ A plastic milk crate ■ Several 5-pound weights

Tools ■ None

Safety Precautions ■ No preexisting upper extremity and back injuries ■ Remind each volunteer not to overexert

Procedure 1. Place milk crate on a stable surface about waist high, such as a desktop. 2. Put 3 weights (15 pounds) in the crate. 3. Have a volunteer lift and set down the crate several times. 4. Place the same milk crate with weights on the floor. 5. Have another volunteer lift and set down the crate several times.

Evaluation ■ Observe volunteers during this activity ■ Note when they begin to tire and stop the activity

Questions 1. Which level provided an easier lift? THE BACK 2. Why?

3. Explain how the two positions of the milk crate affected the volunteers?

4. Based on this activity, what changes could be made at the jobsite to reduce the possibility of injury?

The Back and Why It Hurts 71