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NIOSH Publication No. 2007-122:Simple Solutions: Ergonomics for Construction Workers |
April 2007 |
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Simple Solutions for Overhead Work:The ProblemOn some construction jobs you need to work overhead, reaching up with one or both arms raised above your shoulders. Your head may be tilted back, looking up to see what you are doing. Whether you are drilling, driving fasteners, or finishing drywall, overhead work puts stress on your shoulders and neck. Eventually it may lead to serious muscle and joint injuries. You are at risk of injury if you do this work often or for long periods of time. The risk is increased if you frequently hold tools, equipment, or materials above the height of your shoulders, or if you twist your body while your arms are in an awkward, raised position. When you work with your arms raised, injuries are even more likely if you have to use repetitive movements or a lot of force. For example, using some hand tools overhead requires you to repeat the same motions over and over, as well as apply force, while you are reaching up. Lifting, holding, and positioning heavy or awkward objects while your arm is raised can also require force. Working overhead also may reduce your ability to do the job safely and productively. For example, you are at risk of many types of injury if your vision is obstructed, if you have an unstable footing, or if you have trouble holding or positioning a tool. Injuries & DisordersBelow are some of the injuries you may develop when you work overhead. Shoulder. Shoulder pains and injuries are usually the result of overworking the shoulder. When you keep your arm raised above your shoulder (or keep your arm stretched out), your shoulder begins to ache after a short time. It tires easily. The muscles in your shoulder are connected to your arm by tendons. Between the tendons and bones are small sacs of fluid called bursa. They lubricate the shoulder so it moves easily. Continual stress on your shoulder can cause the bursa to get squeezed, swollen, stiff, and inflamed (bursitis). Bursitis can make it painful, or even impossible, to raise your arm. Continual stress on the shoulder can also cause the shoulder tendons to become inflamed, resulting in pain (tendinitis). Another shoulder injury is the rotator cuff tear. The rotator cuff is a group of four muscles and their tendons that wrap around the front, back, and top of the shoulder joint. These let the shoulder function through a wide range of motions. Stress on the shoulder may cause them to tear, which can make routine activities difficult and painful. A NIOSH review of studies found that the risk of developing shoulder pain or a shoulder muscle or joint disorder is increased by the combination of frequently working with raised shoulders (60° or more), using repetitive arm or shoulder movements while in this position, and applying force while in this position. Neck. The neck is a complicated structure composed of seven bones called cervical vertebrae, one below another. It also has cartilage, nerves, muscles, and ligaments (long fibers supporting the muscles). When you keep your neck bent forward or backward, or bend it frequently, the muscles work harder and the ligaments flex and stretch. Eventually the ligaments can partially tear, resulting in a neck sprain. Another common condition is tension neck syndrome. This is muscle strain that results from long periods of looking up. It can cause neck stiffness, muscle spasms, and pain in the neck or radiating from the neck. It is also possible to develop arthritis in the neck. The risk of arthritis increases for workers who already have had a neck injury and still do overhead work. According to a 1997 NIOSH study, your risk of developing neck pain or a neck musculoskeletal disorder is increased by the combination of frequently working with your neck flexed (15° or more), using repetitive movements, and applying force while in this position. Some SolutionsOverhead work cannot be eliminated from construction, but it is possible to change how you do it so it is easier on your body. Solutions are available that can reduce the level of stress on your shoulders, neck, and arms. They may also reduce how often and how long the body is subjected to this stress. Many of the solutions can also eliminate other potential safety hazards and increase productivity. The type of task and the site conditions will determine which solutions are best for you. A few possible solutions for specific overhead tasks are explained in Tip Sheets #6-9. General solutions for doing overhead work with less risk of injury include: Change materials or work processes. One of the most effective solutions may be to use materials, building components, or work methods that are less labor-intensive, so the task takes less time and you reach overhead for a shorter period. For example, installing embedded concrete inserts into ceiling forms would eliminate the prolonged overhead drilling needed to place all-thread rods for ceiling systems. An individual construction worker or subcontractor usually cannot make a decision like this. Certain changes may require the approval of the building owner, architect, engineer, or general contractor. Change tools and/or equipment. For example, use bit extensions for drills and screw guns that allow you to hold the tool at waist or shoulder level rather than above your head. Use mechanical lifts or hoists to raise and position building materials rather than lifting them manually. Or use a lift to raise yourself so you are closer to the work. In a few cases, cost and site conditions may restrict the use of such equipment. Change work rules and provide training. Contractors can encourage the use of equipment like extensions, lifts, and hoists that reduce the need for workers to raise their arms. Site rules can limit the amount of time that workers do overhead work without a break. Also, a policy of providing ergonomics training may help workers more quickly identify potential problems and find effective solutions. Page Content:TIP SHEET #6 Bit Extension Shafts for Drills and Screw Guns TIP SHEET #7 Extension Poles for Powder-Actuated Tools TIP SHEET #8 Spring-Assisted Drywall Finishing Tools TIP SHEET #9 Pneumatic Drywall Finishing Systems TIP SHEET #6 Bit Extension Shafts for Drills and Screw GunsThe Problem If you use a drill or screw gun for overhead work, you are forced to keep your arms and neck in fixed, awkward, hard-to-hold positions. You have to push upward with a heavy tool above your shoulders, using your shoulder muscles instead of your biceps. One SolutionUse a bit extension shaft for the drill or screw gun, so you can hold the tool below your shoulder and closer to your waist. You strain your arms, neck, shoulders, and back less because you don't have to hold the tool above your shoulders or work in an awkward position. You work with your upper arms held close to your sides, and your hands in front of your body. You are pushing with your biceps muscles instead of your shoulders. How It Works The extension is like a normal socket, but longer. It can be made from carbon steel tube stock. One end of the tube is welded to a piece that fits into the drill or screw gun chuck. An impact socket is welded onto the other end of the tube. A bit can then be Extensions are available from several manufacturers in many different lengths and diameters. Lengths generally run from 12 to 40 inches. It is also possible to make your own extension. Before using an extension for drilling or fastening, you should determine whether it is appropriate for the job. Benefits for the Worker and EmployerBit extensions should reduce a worker's chance of developing muscle and joint injuries. Workers benefit from not having to hold a heavy tool above their shoulders for long periods. The extension itself weighs less than two pounds. Using the extension is easy after a little practice. One company that uses the extensions says that their workers like the way the extension prevents shoulder strain. However, an extension does not solve the problems caused by holding your neck tilted back to look up at your work. To cut down on neck strain, avoid looking up when you don't have to. To be safe, make sure you push the extension onto the drill chuck tightly, efore you turn on the power. In a screw gun, the screw must also be tight in the bit. Approximate CostYou can make your own bit extension, which will cost $1-2 for materials plus labor. Manufactured bit extensions cost from approximately $12 for a 12-inch model to $45 for a 24-inch model. 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TIP SHEET #7 Extension Poles for Powder-Actuated ToolsThe ProblemUsing powder-actuated fastening tools (PATs) for overhead work may lead to serious shoulder, arm, and hand injuries. You work with your arms above your shoulders, an awkward position that may cause sore muscles and joints. Sometimes you have to hold this difficult position for a long time, or repeat the position over and over during your shift. This can cause fatigue and eventually lead to arm and shoulder problems like bursitis or rotator cuff tendinitis.
One SolutionUse an extension pole for overhead work. This is a fixed height or modular pole attached to the powder-actuated tool. Using the extension, the tool is entirely out of your hand. All you have to do is squeeze the trigger. You no longer need to raise your arms above your shoulders and hold them there to work on the ceiling. The extension does it for you. The extension lets you keep a more neutral body posture. Your arms are closer to your body and below your shoulders. This cuts down on the risk of injury to your shoulders, arms, and hands. There is also less recoil shock directed to your shoulders and neck. In addition, you can work on the ground rather than using a ladder, scaffold, or lift.
How It WorksThe powder-actuated tool attaches to the top of the pole. A hand trigger (like a motorcycle brake) is attached to the bottom of the pole. You need only squeeze the trigger to operate the tool. The extension pole can be either fixed height or adjustable. Lengths of available extensions range from 3 to 18 feet, though poles longer than 8 feet may be too difficult to position and control. The gun must be held tight to the substrate at a 90-degree angle until the firing is complete. Benefits for the Worker and EmployerWorkers have less chance of developing a shoulder, arm, and hand injury. With the tool attached to the pole, you can keep your arms below your shoulders. You will also feel less recoil shock at your shoulder. Moreover, with the gun further from your head, the noise exposure will be lower. Using the pole will also keep your eyes and face further from the concrete dust and debris. You do still need to look up to position the shot, which puts some strain on your neck. Productivity may improve when there is less setup time using the tool extension, because there are no are no ladders, scaffolds, or lifts needed. Approximate CostA modular pole assembly costs from $300-400. However, if ladders, scaffolds, or lifts were rented for this work in the past, you will no longer have this cost. For More Information
TIP SHEET #8 Spring-Assisted Drywall Finishing ToolsThe Problem If you use typical flat and corner "mudboxes" for drywall finishing, you With a flat box, you often have to push
hard while bending your wrist and back. When you bend like this while pushing forcefully, you increase your chance of developing a muscle or joint injury. Your risk is higher when you do the same job Finishers say that corner boxes require them to push even harder than flat boxes, because you have to squeeze the compound into a tighter space. One SolutionUse a spring-assisted finishing tool. This does most of the pushing for you. Spring-assisted flat boxes and corner tools are available that cut down significantly on the strain caused by pushing. With spring-assisted flat boxes, the springs provide up to 75% of the force needed to push the compound onto the wall. Spring-assisted corner tools provide 100% of the force needed to finish corners. How It WorksSpring-assisted flat boxes look and work just like regular boxes. The box wheels activate the power assist feature. Springs on the outside of the box pull on levers. The levers then push on a pressure plate, and the compound squirts out when the wheels touch the wall. The boxes come in several different widths and with different handle lengths. Spring-assisted corner finishers have hydraulically damped springs. When you turn a handle, the spring pushes the compound through a normal corner-finishing head. All you need to do is guide the tool down the corner. You use a regular pump to fill both types of spring-assisted tools with compound. Benefits for the Worker and EmployerA spring-assisted mudbox should reduce a worker's chance of developing a muscle or joint injury. More than 80% of the workers involved in one study liked using the new tools much better than the older ones. After using both new tools, all workers in the study said they were not as tired as when using the regular tools. Most said they had less pain. The same study suggested that there were gains in productivity. Spring-assisted flat boxes gave the same results and were just as fast as regular boxes. However, they led to less worker fatigue and pain, and workers said they got more done because they were less tired. They also were able to use the new boxes for a longer time without becoming fatigued. In addition, most workers said that the new spring-assisted corner tool was faster and easier to use, compared to the older corner boxes. Approximate CostYou can rent or purchase these tools. Rentals cost about the same as for regular boxes. One manufacturer sells a set of three spring-assisted flat boxes for about $1,300 and a spring-assisted corner finisher for about $1,400. For More Information
TIP SHEET #9 Pneumatic Drywall Finishing SystemsThe Problem Finishing drywall by hand requires lots of effort and repetition. Your body is forced into awkward positions that can lead to serious wrist, shoulder, arm, and back injuries. The combination of pushing and working in an awkward position causes fatigue as well as tired and sore muscles. Eventually it can increase your chance of developing a muscle or joint injury. One SolutionUse a pneumatic drywall finishing system. You can avoid hand finishing, and you won't have to use flat and corner boxes. Although the work will still require some awkward positions and motions, you will not be exerting high forces at the same time or for as long a time. An air compressor gives enough pressure to force the drywall compound through the flat- and corner-finishing heads of the pneumatic system. The pneumatic system requires much less physical effort than hand finishing, and it cuts down on the repeated wrist, arm, and and back movements. It also takes less effort to use than the automatic tools. You do not need to push with the same strong force used with boxes. You only have to guide the powered tool down the corner. How It WorksAn air compressor forces the drywall compound from the hopper into a tube. You do not need to hand pump the compound. Air forces the compound through the head of the tool when you pull the trigger. The heads give the same quality of finish that boxes do. The tool requires an airline from the hopper to the applicator. You also need electrical power for the air compressor. Benefits for the Worker and EmployerThese systems should reduce a worker's chance of developing muscle and joint injuries. In one study, most workers who tried the pneumatic system liked it better than the regular tools. Workers reported that their muscles were not as tired, and they did not have as much pain after using the pneumatic system. There can also be an improvement in productivity. Workers in the study said the pneumatic system is faster than the older finishing boxes. Some workers said that it took a while to learn the new system. Although using the system was slow at first, it became faster within two months. There are some drawbacks to the pneumatic system. The air and electrical lines may restrict your movement while you work. The new system also takes longer to move, set up, and clean than hand finishing equipment. Therefore, it may not be as practical for small finishing jobs. Approximate CostPneumatic finishers start around $3,500 and cost more depending on features. For More Information
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