Two workers demonstrating proper lifting techniques when materials are too heavy/large for one person.  They are also utilizing the appropriate PPE.  (Photo courtesy of David Risner)  

According to EHS today, Tasks such as carrying boxes or lifting crates lead to hundreds of thousands of injuries a year.  Here are some steps you can take to assess the risks in your workplace and reduce this costly occupational hazard.

In the workplace, we can view manual materials handling (MMH) as any process in which the human operator is asked or required to lift, lower, push, pull, carry or perform any other similar task in which an object is moved through space solely under the power of the human operator.  Additionally, some assisted activities such as pushing a cart or using a mechanical assist still may be viewed as a manual materials handling task.

Many in the work force view materials handling tasks as only those tasks that involve weights that are perceived as heavy.  In truth, MMH involves any handling of a product, whether it is a pencil or a 70-pound piece of electronics equipment.  MMH is not relegated solely to heavy manufacturing environments; it includes jobs in a plant where a person has to lift a 1-pound component and jobs in an office where a person must lift a 55-pound computer monitor.

Is MMH a Health and Safety Risk?

Manual materials handling is a known risk in industry period.  There should be no argument.  More than enough data is readily available to prove this point.  When looking at injury and illness statistics, musculoskeletal disorders related to MMH seem to fall into several categories:

  • Accident Worker loses balance or control of the load and gets injured, often in the form of a muscle strain;
  • Overexertion Worker attempts to lift a heavy load or conditions of a lift have high physical demands (e.g., task requires awkward handling or extreme postures);
  • Fatigue induced High frequency handling of a load that is within a worker's capability begins to "wear down" the body and yields an injury (the cumulative trauma model).

Reducing the Risk of MMH

The first step in addressing MMH in a facility is to admit that there is a problem manual materials handling is a risk that requires a resolution.  The second step is to look at MMH from a slightly different perspective, as simply a part of the business that needs to be designed for safety, efficiency and productivity.  Instead of running straight to the NIOSH lifting equation or the Liberty Mutual tables, a common risk-based approach in ergonomics, adopt the goal to eliminate MMH whenever possible simply because it is a risk.

Does the load need to be moved at all?

The first question that should be addressed when evaluating a MMH process is whether the load needs to be moved at all.  Sometimes the most important question to ask is, "Why are we doing this?"  If there is no specific value to moving a load, then don't do it.  If unnecessary tasks can be eliminated, risk can be reduced and efficiency can be gained.

Is there unnecessary duplication in the movement of materials?

This second question can have the exact same impact on the process.  Unnecessary handling of loads, re-handling of loads and duplication of processes are clear signs of a wasteful system.  Achieving a direct line of flow for a load will reduce the number of times it is handled, resulting in reductions in damage to loads from frequent handling, reduction in risk to employees and, once again, improved efficiency in the process.

Therefore, if a process is simply evaluated to ensure there is a well-planned, efficient movement of loads, ergonomics benefits will already be realized.

Ergonomics Risk Assessment of MMH

It is at this point in the process that a risk assessment of the task will help to determine the level of need (i.e. cost) for the solution.  There are three main methods of risk assessment that are readily available for health and safety professionals to use: 

  • NIOSH Lifting Equation (NLE), 
  • Liberty Mutual Tables (LMT) and 
  • The University of Michigan Energy Expenditure Prediction (EEEP) model.  

Before using any of these tools, it is highly recommended that the analyst receive some training and be aware of the tools' strengths and weaknesses, and the type of information they can provide.

Depending on the outcome of the risk assessment, the type of control can be determined and justified.  Basically, the higher the risk, the greater the need for an engineering control. If the risk is severe enough (e.g., NIOSH lifting index >3; LMT population capable <10 percent), then a mechanical assist may be necessary.  If the risk assessment produces results that are moderate, then the decision becomes a little more challenging.

Controlling the Risk

Once the level of risk is determined for the MMH task, the next step is to determine the best method of controlling the risk.  The first two questions in the flowchart revolved primarily around engineering concerns and the efficiency of the system.  The question of controlling the risk is a choice between engineering, work practice and administrative controls, which revolves around health and safety concerns and the economic feasibility of the solution.

Choosing between these solution options can be fairly easy if one simple question is answered "Do you have any money?"  If the answer is NO, then engineering controls have to go.  If you have a little money, then all the options are possible with some creativity, and if you have a lot of money, anything is possible.  Of course, just because money is available does not mean that the most expensive solution should be chosen.

A good approach to use to help determine the best solution for the task is to perform "What if?" scenarios.  By predicting the potential impact of a solution, the risk assessment tools can be used to determine the effect on risk.  The key is to predict the type of changes that can be expected from the different solutions (e.g., lifting training vs. lift table).  The solution that produces the greatest reduction in risk could be a winner.

To read more on this article, please visit EHS: Reducing the Risk of Manual Materials Handling

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