The Billion-Dollar Ergonomics Opportunity

The Liberty Mutual Workplace Safety Index identifies the leading causes of the most disabling U.S. workplace injuries based on workers’ compensation claims and cost. The 2010 Index reported the 10 most common injuries and illnesses that accounted for over $45 billion in direct workers’ comp costs. Overexertion injuries, defined as caused by excessive lifting, pushing, holding, pulling or throwing, represented the largest proportion of injuries and cost American companies over $1 billion a month.

Over the last 20 years or so, companies have focused on implementing ergonomics improvement processes with the most successful companies focusing on engineering controls. These efforts have paid off as the cost (and incidence) of repetitive motion injuries (RMI) have decreased 44 percent in the last 11 years. Unfortunately, the cost of overexertion injuries has decreased only 5 percent and actually is on the rise, with an increase of about $700 million a year.

Why the difference in impact between RMIs and overexertion injuries? While it is true that applying ergonomics principles in the workplace will solve both RMIs and overexertion injuries, the investment required often is quite different.

The risk factors for RMIs and overexertion injuries are similar; both result from job tasks that exceed the limits of human capability for posture, force and frequency. However, for RMIs, the risk level can be reduced by making changes to the geometry of the workstation and equipment (bench heights, reach distances or tool modifications).

Unfortunately, the primary problem contributing to many overexertion injuries is the force required to complete the task. Here on earth, there are only two ways to address this issue: provide a mechanical device to aid the person in handling the task or reduce the force required. Both options are more difficult than simple workstation geometry problems and usually more costly.

Our challenge is clear: We need to know where to spend our time and resources.

Analyzing the problem

Since the solution to most overexertion issues generally requires financial resources, which often are limited, the challenge is to invest in the right solutions to the right problems. Fortunately, there are tools to help analyze the issues, determine priorities and determine effective countermeasures. The two most widely used methods are the NIOSH Lifting Equation, to analyze lifting and lowering, and the Liberty Mutual Push/Pull Tables, to analyze pushing and pulling. Both are available in traditional paper versions, but a quick search within a mobile app store will give you access to auto-calculators of equations.

More advanced methods to assess material handling tasks use 3-D modeling within current digital engineering software. There are ergonomics- and human factors-centered CAD packages as well; these methods provide a lot more information regarding burden. If you are ready to take your ergonomics process beyond counter-measuring risk in your existing operations, these advanced methods are great. But a significant investment in training is required. To complete this type of analysis, the operator must have substantial educational background and experience in ergonomics/human factors.

The NIOSH Lifting Equation

Twenty or so years ago, the National Institute for Occupational Safety and Health (NIOSH) commissioned a panel of research experts to develop a model to determine if a lifting task was “safe” for the majority of the work force. This resulted in the development of the NIOSH Lifting Equation, and it has been widely used by safety professionals since its creation.

The primary NIOSH Lifting Equation outputs the recommended weight limit (RWL) for a particular task, which is defined as the weight that the majority of the work force is capable of lifting safely, given their specific job geometry, frequency and duration of lifting. It is the “not-to-exceed” number for a particular two-handed lifting task, or the highest weight at which the working population (99 percent of men and 75 percent of women) safely can perform the lift. The highest possible RWL is 51 pounds, given the ideal lifting scenario (working in the comfort zone with no twisting, load in close to the body, lifting once every 5 minutes for 1 hour out of the day).

The equation considers six factors – or multipliers – to determine the RWL: horizontal distance, vertical location, travel distance, angle of asymmetry, coupling and frequency, in addition to the amount of total time spent lifting (duration). Other criteria also must be met, but the equation is valid for most two-handed lifting scenarios encountered in industry. The NIOSH Lifting Equation can be used to:

➤ Evaluate existing and proposed lifting conditions to identify job hazards and indicate when people may be working outside of their capabilities.

➤ Prioritize hazardous jobs for ergonomic intervention. Existing lifting conditions that are not acceptable can be ranked and ordered by degree of burden based on the Lifting Index. ¹

➤ Highlight opportunities for reducing lifting hazards. Based on the multipliers, we can determine the easiest change with the highest impact. Understanding the multipliers can help you make decisions and answer that driving question: “How do I get the biggest bang for my buck?”

¹Lifting Index is a ratio of what is actually being lifted to what the equation says you can lift (RWL). An LI greater than 1.0 means you are lifting more than what NIOSH recommends for your task. The higher the Lifting Index, the higher the likelihood of injury. Ideally, LI should be below 1.0.