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Course 722 - Ergonomics Program Management

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Controlling Risk Factors


Rid the Job of Risk Factors

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.

The Hierarchy of Hazard Control Strategies

Controlling exposures to occupational hazards is the fundamental method of protecting workers. Traditionally, 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 employer employ the following hierarchy of hazard control strategies:

  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. 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 an ergonomics hazard. Some obvious examples of elimination include eliminating the need to carry heavy containers by replacing them with smaller containers. You can substitute that old office chair with a new ergonomically designed chair.

These strategies are considered first because they have the potential of completely eliminate the hazard, thus greatly reducing the probability of an accident. Redesigning or replacing equipment or machinery may be expensive, but remember that, according to the National Safety Council, the average direct and indirect cost of a lost work time injury more than $38,000 and most injuries in the workplace are ergonomics-related.

Check out this short audio clip by Dan Clark of the Good workstation planning with effective ergonomics will also help guarantee worker safety.

Engineering Controls

The preferred approach to prevent and control MSDs is to design the job including:

  • the workstation layout
  • selection and use of tools
  • work methods to take account of the capabilities and limitations of the work force

A good match, meaning that the job demands pose no undue stress and strain to the person doing the job, helps ensure a safe work situation.

Engineering controls are preferred because they may completely eliminate the hazard. No hazard: No injury! They also do not rely on human behavior nor do they require continual oversight to work. Finally, engineering controls may save the company far more than the initial investment. Engineering control strategies to reduce ergonomic risk factors include the following:

  • Changing the way materials, parts, and products can be transported. For example, using mechanical assist devices to relieve heavy load lifting and carrying tasks or using handles or slotted hand holes in packages requiring manual handling.
  • Changing the process or product to reduce worker exposures to risk factors. Examples include maintaining the fit of plastic molds to reduce the need for manual removal of flashing or using easy-connect electrical terminals to reduce manual forces Modifying containers and parts presentation, such as height-adjustable material bins.
  • Changing workstation layout. Examples might include using height-adjustable workbenches or locating tools and materials within short reaching distances.
  • Changing the way parts, tools, machinery and materials are to be manipulated. Examples include using fixtures (clamps, vise-grips, etc.) to hold work pieces to relieve the need for awkward hand and arm positions or suspending tools to reduce weight and allow easier access.
  • Changing tool designs. For example, pistol handle grips for knives to reduce wrist bending postures required by straight-handle knives or squeeze-grip-actuated screwdrivers to replace finger-trigger-actuated screwdrivers.
  • Changes in materials and fasteners. For example, lighter-weight packaging materials to reduce lifting loads.
  • Changing assembly access and sequence. For example, removing physical and visual obstructions when assembling components to reduce awkward postures or static exertions.

Work Practice and Administrative Controls

Work practice and administrative controls are closely related attempts to change behaviors. They are management-dictated work practices and policies to reduce or prevent exposures to ergonomic risk factors. Work practice and administrative control strategies include:

  • Changes in job rules and procedures such as scheduling more rest breaks
  • Rotating workers through jobs that are physically tiring
  • Training workers to recognize ergonomic risk factors and to learn techniques for reducing the stress and strain while performing their work tasks

Although engineering controls are preferred, work practice and administrative controls can be helpful when engineering controls are not technically feasible. However, since work practice and administrative controls focus on eliminating or reducing exposure (not the hazard itself), they require diligent management, training, supervision, and enforcement to be effective. They work only as long as people behave!

Common examples of administrative control strategies for reducing the risk of MSDs are as follows:
  • 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
  • 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

Check out this short audio clip by Dan Clark of the Stretch breaks for employees have big benefits. You lose a little production time, but make bigger gains in productivity. In this podcast, Dan mentions many computer and mobile apps to schedule and time a stretch break.

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)is effective. Some consider these devices to be personal protective equipment (PPE).


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 question.

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 manual handling job tasks [NIOSH 1994]. A recent epidemiological study credits mandatory use of back belts in a chain of large retail hardware stores in 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. More on backbelts.


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?

There you have it! Almost everything you need to know about ergonomic control strategies, right? Well, not quite, but you do have a good introduction to them. Remember, ergonomics control strategies may not be immediately obvious. If you can't figure out an effective solution, don't forget to take advantage of an outside expert. Participating in the consultation process with an ergonomist is a real win-win for your company and an excellent education for you.

Time to take the module review quiz, so let's go. Answer each question as best you can. Scroll up the page to review if you like.


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. All of the following are ergonomics control strategies, except _____.

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

3. Which of the following is not an advantage of employing engineering controls?

4. Changing the tools, equipment, machinery, and materials used by an employee is an example of which control strategy?

5. Which of the following is not a characteristic of work practice and/or administrative controls?

Have a great day!

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