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Variables in the NIOSH lift equation are the same task variables that can be affected by ergonomic intervention to reduce the risk of lifting injuries. The basic ergonomic principles related to these variables include:

• Weight: Reduce the weight of the materials handled by one person to as low as possible.
• Frequency: Reduce the number of times a material has to be handled. Allow sufficient time for recovery between lifting when repetitive lifting is required and cannot be avoided.
• Horizontal Distance: Reduce the horizontal distance to lift from the body to as small as possible. Remove any obstacles or work designs that force the person to reach and lift materials away from the body.
• Positioning: Position materials to be lifted on elevated pallets, tables, conveyors or shelves at a height as close to 30-33 inches as possible (in most cases). Minimize the need to lift from high (above shoulders) or low positions (below knuckles).

An anthropometric percentile chart as shown below can be used work design. If possible, for general work populations comprised of male and female workers, arrange the lowest position to be based on the 95th percentile for males and the highest position to be based on the 5th percentile female. For example, using the chart below, arrange the lowest hand placement for lifting at knuckle level for the 95th percentile male, 82.55 cm or 32.5 inches. Design the highest hand placement for lifting to shoulder level to be based on the 5th percentile female, 124.09 cm or 49 inches. Therefore the ideal range for hand placement during lifting would be 32.5 inches to 49 inches. This range would allow lifting in the safe work zone for the majority of the population, both female and male.

Dr. Richard Bunch, CEO of WorkSaver lectures each year at the National Ergonomics and Exposition Conference on the topics of aging and ergonomics.

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