Analyzing jobs to identify factors associated with risks for WMSDs, as discussed in Step 4, lays the groundwork for developing ways to reduce or eliminate ergonomic risk factors for WMSDs. A variety of approaches can help to control these risk factors.

Types of Controls

A three-tier hierarchy of controls is widely accepted as an intervention strategy for controlling workplace hazards, including ergonomic hazards. The three tiers are as follows:

• Reducing or eliminating potentially hazardous conditions using engineering controls
  
  
• Changes in work practices and management policies, sometimes called administrative controls
  
  
• Use of personal equipment

Engineering Controls

The preferred approach to prevent and control WMSDs is to design the job including (1) the workstation layout, (2) selection and use of tools, and (3) work methods to take account of the capabilities and limitations of the workforce. A good match (meaning that the job demands pose no undue stress and strain to the working population as a whole) helps ensure a safe work situation. On the other hand, the presence of risk factors as described in Step 4 represents departures from this goal and would indicate the need for control measures. 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, which might include using height-adjustable workbenches or locating tools and materials within short reaching distances
  
  
• Changing the way parts, tools, 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 (e.g., removing physical and visual obstructions when assembling components to reduce awkward postures or static exertions)

Figure 2 applies a number of these options for controlling the risk factor situations illustrated earlier in Figure 1. Exhibits 15 and 16 illustrate NIOSH efforts to advise companies about engineering control strategies to reduce WMSDs.

Administrative Controls

Administrative controls are management-dictated work practices and policies to reduce or prevent exposures to ergonomic risk factors. Administrative control strategies include (1) changes in job rules and procedures such as scheduling more rest breaks, (2) rotating workers through jobs that are physically tiring, and (3) 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, administrative controls can be helpful as temporary measures until engineering controls can be implemented or when engineering controls are not technically feasible. Since administrative controls do not eliminate hazards, management must assure that the practices and policies are followed. Common examples of administrative control strategies for reducing the risk of WMSDs 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 WMSDs and instruction in work practices that can ease the task demands or burden

Two examples of administrative measures are described in Exhibits 17 and 18.

Personal Equipment: Is It Effective?

One of the most controversial questions in the prevention of WMSDs 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). 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. In the health care management section (Step 6), the use of wrist splints or immobilization devices is also briefly discussed.

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. This area is being researched, and the questions about the effectiveness of most personal equipment remain open. 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?

Implementing Controls

Ideas for controls can be derived from a variety of sources:

• Trade associations may have information about good control practices for addressing different problem operations within an industry
  
  
• Insurance companies that offer loss control services to their policyholders
  
  
• Consultants and vendors who deal in ergonomic specialty services and products
  
  
• Visits to other worksites known to have dealt with similar problem operations

Ideas from these sources are in addition to those ideas gained from brainstorming with employees who perform the jobs or from work teams engaged in such problem solving.

Implementing controls normally consists of

• trials or tests of the selected solutions,
  
  
• making modifications or revisions,
  
  
• full-scale implementation, and
  
  
• follow up on evaluating control effectiveness.

Testing and evaluation verify that the proposed solution actually works and identifies any additional enhancements or modifications that may be needed. Employees who perform the job can provide valuable input into the testing and evaluation process. Worker acceptance of the changes put into place is important to the success of the intervention.

After the initial testing period, the proposed solution may need to be modified. If so, further testing should be conducted to ensure that the correct changes have been made, followed by full-scale implementation. Designating the personnel responsible, creating a timetable, and considering the logistics necessary for implementation are elements of the planning needed to ensure the timely implementation of controls.

A good idea in general is that ergonomic control efforts start small, targeting those problem conditions which are clearly identified through safety and health data and job analysis information. Moreover, the control actions can be directed to those conditions which appear easy to fix. Early successes can build the confidence and experience needed in later attempts to resolve more complex problems.

Evaluating Control Effectiveness

A follow up evaluation is necessary to ensure that the controls reduced or eliminated the ergonomic risk factors and that new risk factors were not introduced. This follow up evaluation should use the same risk factor checklist or other method of job analysis that first documented the presence of ergonomic risk factors. If the hazards are not substantially reduced or eliminated, the problem-solving process is not finished.

The follow up may also include a symptom survey, which can be completed in conjunction with the risk-factor checklist or other job analysis method. The results of the follow up symptom survey can then be compared with the results of the initial symptom survey (if one was performed) to determine the effectiveness of the implemented solutions in reducing symptoms.

Because some changes in work methods (and the use of different muscle groups) may actually make employees feel sore or tired for a few days, follow up should occur no sooner than 1 to 2 weeks after implementation, and a month is preferable. Recognizing this fact may help avoid discarding an otherwise good solution.

In addition to the short-term evaluations using job analysis methods and symptom surveys, long-term indicators of the effectiveness of an ergonomics program can include

• reduction in the incidence rate of musculoskeletal disorders,
  
  
• reduction in the severity rate of musculoskeletal disorders,
  
  
• increase in productivity or the quality of products and services, or
  
  
• reduction in job turnover or absenteeism.

The above-mentioned indicators offer bottom-line results in evaluating interventions that have been put into place. Other indicators may also be used that represent in-process or interim accomplishments achieved on the path to building an ergonomic program for example, the extent of the ergonomic training given the workforce, the number of jobs analyzed for potential problems, and the number of workplace solutions being implemented. While bottom-line results are most telling in terms of defining a successful program, the interim measures allow the total development to be monitored.

Exhibit 19 describes evaluation techniques used in ergonomic programs at meat packing plants.