The Lifting Guideline* incorporates a number of key variables in assessing the risk of injury associated with lifting. It provides a more useful approach than single-weight limits.
Review the task in question and measure the following variables, using a tape measure and a watch.
LI ≤ 1: Acceptable
LI ≥ 1: Some individuals at risk
LI ≥ 3: Most individuals at risk
See below for more information on understanding what the formula does.
Basic on-line calculator
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This guideline was developed by the National Institute for Occupational Safety and Health (NIOSH) and has become accepted internationally as the gold standard for lifting. The criteria used to establish this guideline included a review of biomechanics, physiology, and the most pertinent studies of back injuries. The first version of the guideline was published in 1981. A second version published in 1991 added more variables. Future versions are likely to be published with additional variables as sufficient data is gained to understand the effect on safe lifting.
For a complete downloadable guide see NIOSH Lifting Guide
NIOSH is part of the U.S. Department of Health and Human Services and is charged with research and education. In contrast, the Occupational Safety and Health Administration (OSHA) is part of the U.S. Department of Labor and is charged with enforcement.
(Hand-to-container coupling classification)
Good – Item has optimal handle/handhold, i.e. a comfortable grip in which the hand can be easily wrapped around the object:
Fair – Item has sub-optimal handle/handhold; or no handle but easily held, like a standard cardboard box.
Poor – Does not meet above requirements, rough or slippery surface, sharp edges, asymmetric center of mass, unstable contents, or require gloves
RWL: Recommended Weight Limit — the acceptable weight that can be lifted under the parameters that you input.
51: This is 51 lbs., an acceptable weight for most people when:
10/H: This factor takes into account the Horizontal distance the load is from the spinal column.
For example: If H is 20 inches, then 10/20 = 0.5
0.5 x 51 lbs = 25.5 lbs
Thus, 51 lbs. is acceptable when held against the body, but when the load is extended away from the body, the recommended weight limit drops to 25.5 lbs.
(10 inches is the thickness of the torso; it is not possible to hold the load closer. Holding the load an additional 10 inches away from the body creates an H of 20.)
V factor: This is the most complicated to explain.
30: This is 30 inches, knuckle height (or waist height – the difference is not meaningful here)
| V-30 |: The absolute value of V-30
For example, if V=10 (i.e. your hands holding the load are 10 inches above the floor), then 10 – 30 = –20. Then, the absolute value of –20 is simply 20.
0.0075 x 20 = 0.15
1 – 0.15 = 0.85
0.85 x 25.5 lbs. (from the example above) = 22.7 lbs.
Thus, 51 lbs. can be held against the body, but the recommended limit drops to 25.5 when held away from the body, and further drops to 22.7 lbs. when the load is close to the floor.
As another example, if V=50 (i.e. your hands 50 inches above the floor), then 50-30 = 20. The absolute value of 20 is still 20.
As above, following through with the math yields a factor of 0.85 and a recommended limit of 22.7 lbs.
In short, 30 inches above the floor is ideal (from this perspective). Any vertical distance above or below this level reduces the recommended limit. Using the absolute value is the mathematical way to make this work.
D: The vertical Distance moved. Anything more than 10 inches reduces the safe limit.
A and C: The pattern should now be evident — any factor that comes into play reduces the recommended limit.
F: Frequency of lift. Note that in the Frequency Table, starting at >9 lifts per minute (depending upon duration and the V factor), the factor drops to zero. Multiplying the zero in the formula yields a RWL of 0, i.e. above the maximum and the lift should not be performed at this rate. Also note that the frequency factor affects the RWL more than any other factor.