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Course 711 - Introduction to Ergonomics

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Controlling Risk Factors

Eliminating Risk Factors

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The Advantages of Ergonomics - OR-OSHA
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Ergonomic improvements are changes made to improve the "fit" between a job and the capabilities of the employees performing it. Analyzing jobs to identify factors associated with risks for MSDs lays the groundwork for developing ways to reduce or eliminate ergonomic risk factors for MSDs.

Ergonomic Hazard Control Strategies

To control ergonomic hazards, a hierarchy of controls has been used as a means of determining how to implement feasible and effective controls. ANSI Z10-2005, Occupational Health and Safety Management Systems, encourages employers to use the hierarchy of hazard control strategies listed below.

  1. Elimination
  2. Substitution
  3. Engineering controls
  4. Administrative controls
  5. Personal protective equipment

The idea behind this hierarchy is that the control methods at the top of the list are potentially more effective and protective than those at the bottom for controlling ergonomic hazards. Following the hierarchy normally leads to the implementation of inherently safer systems, ones where the risk of illness or injury has been substantially reduced. Let's take a closer look at the hierarchy of control strategies.

Elimination and Substitution

Elimination and substitution, while most effective at reducing hazards, also tend to be the most difficult to implement in an existing process. If the process is still at the design or development stage, elimination and substitution of hazards may be inexpensive and simple to implement.

For an existing process, major changes in equipment and procedures may be required to eliminate or substitute for a hazard. For example, if you have to work in a space that requires poor work postures, you might eliminate the need to perform the work within that space. If you have to lift a heavy object, you might substitute the heavy object with an object of less weight.

Engineering Controls

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Engineering controls involve making changes to workstations, tools, or equipment used on the job. These controls are preferred over all others because they make permanent changes that can totally eliminate hazards at the source. Although they may be more expensive to implement than other controls, their effect is often more significant.

Let's take a look at some of the various engineering control strategies that may be effectively used to eliminate hazards.

Workstation Design

Aspects of workstations you can change with engineering controls include:

  • Workspace layout;
  • 711fix
    Different workstation ideas
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  • Work surfaces;
  • Standing and walking surfaces;
  • Seating;
  • Storage;
  • Work fixtures; and
  • Work environment.

Check out this short audio clip by Dan Clark of the theSafetyBrief.com that discusses four detailed reasons why forklifts, conveyors and hoists so workers can avoid sprains, fractures and musculoskeletal injuries.

Computer Workstations

Computer workstations have special considerations you should be aware of. The monitor and keyboard positions, lighting, and seating are especially important in preventing work-related MSDs and eye discomfort. Shared workstations should be easily adjustable so the screen and keyboard can be at the proper level. Take a look at some specific workstation design considerations and problems/solutions for computer workstations.

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Note: We also recommend arm rests for proper support.

There are five components of proper computer workstation design that you must address to maintain proper posture: the work surface; the keyboard; the pointing device or trackball; the monitor; and the chair.

1. Work Surfaces

  • Surface needs to be deep enough to allow proper keyboard positioning and to accommodate a monitor viewing distance of 18-24″.
  • Surface needs to be wide enough to accommodate keyboard, mouse, and reference material.
  • Surface height (or keyboard height independent of the main surface) should be adjusted for the user or adjustable for multiple users.
  • Avoid resting your wrists on a hard or sharp surface (use a wrist rest if necessary).
  • Leave enough leg room to allow your legs to move freely.

2. Keyboards
  • Keyboards should be thin and detachable.
  • Must be positioned low enough to keep wrists straight, shoulders relaxed, and elbows angled between 90 and 120 degrees. (A wrist rest can help you maintain straight wrists.)
  • Alternative keyboards now on the market provide additional options which may alleviate discomfort.

3. Mouse or Trackball

  • Should be within easy reach and at the same height as the keyboard.
  • Trackballs may be a better alternative because they eliminate some arm movement required by the mouse.

4. Monitors

  • Should be positioned so that the top of the screen is slightly below eye level, for a viewing angle of about 30 degrees.
  • The viewing distance should be 18-24″.

5. Chairs

  • Should have adjustable back support that presses firmly against your lower back and extends at least up to mid-back.
  • Should have an easily adjustable seat height to permit your feet to rest flat on the ground with a knee angle of roughly 90 degrees. (some people might need a foot rest to achieve this angle.)
  • Should have a rolling, five-pronged base for stability and to prevent unnecessary twisting.
  • Should have adjustable padded arm rests to support the weight of the shoulders and the arm.
  • Should have an adjustable seat pan to allow the computer user to work comfortably in a forward or reclined position.

Workspace Layout

Workspace layout and arrangement should be carefully designed so that it meets the requirements listed below.

  • The workspace should be adjustable to fit each worker's size.
  • The worker should be able to maintain the neutral position and avoid awkward or extended reaches and jerky movements while performing the task.
  • A full range of motion with adequate leg room, as well as a variety of working positions to avoid static postures should be provided.
  • The worker should have adequate space for access to all necessary tools and equipment, and frequently used tools should be within easy reach.
standing

Work Surfaces

  • Work surfaces should be at the proper height and angle for the individual worker's size, tools, and equipment used.
  • They should permit neutral postures and be adjustable; especially where different kinds of tasks are performed or the workstation is shared.

For example, where workers inspect or assemble small parts, or perform other visually intensive tasks, work surfaces could be tilted to reduce neck, shoulder and arm strain.

Walking and Standing Surfaces

Surfaces on which people stand for long periods should be designed to prevent slipping and provide adequate traction and comfort. Anti-fatigue floor mats, sit-stand stools, and footrests can help make workers more comfortable.

Seating

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Seat-height adjustability and lower back support are important for work done for a long time while seated. Some workers may choose to sit part of the time and stand other times to reduce stress on the body from working in one position too long. Chairs or seating should:

  • adequately support the back and legs;
  • have padded seats;
  • have separately adjustable back and seat cushions;
  • permit feet to be supported either on the floor or with a foot rest;
  • be easily adjustable while seated;
  • be able to swivel for most tasks;
  • isolate the worker from whole-body vibration; and
  • have adjustable arm support when appropriate.

Storage

Storage areas should be organized so that workers maintain good body positions, reduce muscular forces, and avoid excessive reach. Store heavy items between knee and shoulder height. Frequently used items should be stored close to the worker.

Work Fixtures and Tools

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Workers should not have to use their hands or bodies as a vise to hold objects; mechanical devices do this much better. Tooling fixtures and jigs should be set up to avoid awkward postures and excessive forces.

Improper hand tool selection or improper use of tools can cause CTDs. Hand tools should fit the employee's hand; employees with small hands or who are left-handed may need tools designed specifically for these situations. Hand and wrist posture are important because they affect how much force the muscles must produce to hold objects. When selecting and purchasing hand tools, the guidelines listed below should be followed.

  • Select tools that allow the wrist to be held straight and that minimize twisting of the arm and wrist. Good working posture can be maintained when properly designed tools are used.
  • Select tools that allow the operator to use a power grip, not a pinch grip. Minimal muscle force is required to hold objects in a power grip posture. The pinch grip requires excessive fingertip pressure, and can lead to a CTD.
  • Avoid tools that put excessive pressure on any one spot of the hand (i.e., sides of fingers, palm of the hand).
  • For power or pneumatic tools, select tools with vibration dampening built in whenever possible. Provide personal protective equipment such as gel-padded gloves to reduce exposure to vibration.

Work Environment

Workplace environmental factors interact with those the worker and the task brings to the job, and they deserve careful consideration. Below is a list of methods to minimize work-environment hazards.

  • Isolating equipment or operations that produce loud or distracting noise.
  • Making lights bright enough without causing glare.
  • Isolating hands and feet from cold.
  • Reducing whole-body vibration while riding in vehicles or standing near equipment.
  • Isolating workers from excessive heat by providing adequate cooling and ventilation.

Administrative Controls

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Administrative controls are management-dictated procedural and scheduling changes designed to reduce or prevent exposures to ergonomic risk factors. Although engineering controls are preferred, administrative controls may be needed as well, especially when engineering controls can not totally eliminate a hazard or when engineering controls are not technically feasible. Since administrative controls do not eliminate hazards, managers must continually ensure safe procedures and policies are followed to make sure exposure to hazards is minimized.

Common Examples of Administrative Control Strategies

  • Safe procedures should maintain workers in neutral postures and reduce frequency, duration, and severity of exposure to risk factors. Lifting, carrying, pushing, or pulling objects can strain the back, arms, and shoulders. Strength and lifting limits should not be exceeded; extreme muscular exertion can cause injury. Effective lifting techniques should always be used.
  • Broadening or varying the job content to offset certain risk factors (e.g., repetitive motions, static and awkward postures).
  • Adjusting the work pace to relieve repetitive motion risks and give the worker more control of the work process.
  • Training in the recognition of risk factors for MSDs and instruction in work practices that can ease the task demands or burden.
  • Requiring the use of Personal Protective Equipment (PPE) while performing tasks.
  • Reducing shift length or curtailing the amount of overtime.
  • Rotating workers through several jobs with different physical demands to reduce the stress on limbs and body regions.
  • Scheduling more breaks to allow for rest and recovery.

Work Rates

The capacity of workers should be considered in establishing production goals. Increased work rates, excessive overtime, and incentive programs for piece work can cause fatigue, increasing the chance for injury.

Job Enrichment

Tasks involving repetitive motion are major contributors to CTDs. You can minimize repetition by:

  • Using automation, such as in stapling, sorting, labeling, or filling operations; and/or
  • Changing the job to include tasks that don't use the same muscle groups.

For example, in a check-sorting operation, instead of having one person open mail, another stamp them and yet another record the figures, each worker could do each of those tasks.

Personal Protective Equipment

One of the most controversial questions in the prevention of MSDs is whether the use of personal equipment worn or used by the employee (such as wrist supports, back belts, or vibration attenuation gloves) are effective. Some consider these devices to be personal protective equipment (PPE).

backbelt

In the field of occupational safety and health, PPE generally provides a barrier between the worker and the hazard source. Respirators, ear plugs, safety goggles, chemical aprons, safety shoes, and "hard hats" are all examples of PPE. Whether braces, wrist splints, back belts, and similar devices can be regarded as offering personal protection against ergonomic hazards remains open to debate.

Although these devices may, in some situations, reduce the duration, frequency, or intensity of exposure, evidence of their effectiveness in injury reduction is inconclusive. In some instances they may decrease one exposure but increase another because the worker has to "fight" the device to perform his or her work. An example is the use of wrist splints while engaged in work that requires wrist bending.

On the basis of a review of the scientific literature completed in 1994, NIOSH concluded that insufficient evidence existed to prove the effectiveness of back belts in preventing back injuries related to manually handling job tasks [NIOSH 1994]. A recent epidemiological study credits mandatory use of back belts in a chain of large retail hardware stores for substantially reducing the rate of low back injuries [Kraus 1996]. Although NIOSH believes this study provides evidence that back belts may be effective in some settings for preventing back injuries, NIOSH still believes that evidence for the effectiveness of back belts is inconclusive.

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More on backbelts

Still more!

Less controversial types of personal equipment are vibration attenuation gloves [NIOSH 1989] and knee pads for carpet layers [Bhattacharya et al. 1985]. But even here, there can be concerns. For example, do the design and fit of the gloves make it harder to grip tools?

Interim Measures

Interim measures are nothing more than temporary applications of engineering and/or management controls until more permanent solutions can be applied. For instance, if a computer monitor is too low, placing a phone book under the monitor might be an effective temporary solution. Having two people lift heavy objects until a pneumatic lift can be purchased is another example of a temporary fix to the problem.

Safety System Improvements

An effective ergonomics program operates within a larger safety management system that is composed of many interrelated programs. When hazardous conditions and unsafe behaviors exist, it's usually because the safety management system is failing somehow. These failures represent the root causes for accidents and may be categorized as shown below.

  • System Design Failures - Inadequate design of the safety management system. The development of written safety plans, policies, processes, procedures and practices is very important to make sure appropriate conditions, activities, behaviors, and practices occur.
  • System Implementation Failures - Failure to carry out the plan as designed. The ability to effectively implement the safety management system is critical to the success of the system. You can develop a wonderfully designed system, yet if it's not implemented correctly, it won't work.

A missing or inadequate component in any one of these subsystem processes might have a negative impact on ergonomics. Listed below are examples of safety subsystems.

  • Safety training
  • Safety accountability
  • Hazard identification and control
  • Employee involvement
  • Incident/Accident investigation
  • Safety communications
  • Evaluation and improvement

Missing or inadequate safety system components may represent the root causes for ergonomic injuries. Hazardous conditions and unsafe behaviors represent the outward symptoms that give clues about the underlying safety system weaknesses. Therefore, every effort should be made to improve system components to ensure long term workplace safety.

Listed below are some examples of safety system improvements.

  • Including "safety" in a mission statement.
  • Improving safety policy so that it clearly establishes responsibility and accountability.
  • Changing a work process so that checklists are used that include safety checks.
  • Revising purchasing policy to include safety considerations as well as cost.
  • Changing the safety inspection process to include all supervisors and employees.

Notice that in each example we are describing a missing or inadequate process, policy, procedure, plan, or program that may or may not be directly related to ergonomics.

Last Words

Controlling ergonomic hazards requires a balanced approach of both engineering and management control strategies. It's an ongoing effort that needs the help of everyone in the organization.

Back Your Back : Back and Muscle Injury Prevention

Watch this Washington State Dept. of Labor and Industries video that explains the potential causes of back injuries, and discusses ways to prevent back pain. Covers establishing load capabilities and proper positioning. Slides to Video format.

Instructions

Before beginning this quiz, we highly recommend you review the module material. This quiz is designed to allow you to self-check your comprehension of the module content, but only focuses on key concepts and ideas.

Read each question carefully. Select the best answer, even if more than one answer seems possible. When done, click on the "Get Quiz Answers" button. If you do not answer all the questions, you will receive an error message.

Good luck!

1. Which of the ergonomics control strategies is only temporary?

2. Which of the ergonomics control strategies is most effective?

3. Which of the ergonomics control strategies attempt to reduce exposure to an existing hazard through procedures and practices?

4. Which of the following is not listed as a component of proper computer workstation design you must address to maintain proper posture?

5. For proper work surface design, all of these factors should be considered, except _____.

6. Changing work schedules describe which of the three ergonomic control strategies?

7. Effective and safe procedures should incorporate each of the following ergonomics goals, except _____.

8. One of the most controversial questions in the prevention of MSDs is whether the use of interim measures are effective.

9. When hazardous conditions and unsafe behaviors exist, it's usually because _____.

10. Inadequately written safety plans and procedures is an example of a _____.


Have a great day!

Important! You will receive an "error" message unless all questions are answered.