08th September, 2013
## Steps

## Interpretation

### *Background and more information

### Frequency Table

### Coupling Table

#### Definitions

## Understanding the formula

#### Related posts

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.

- Measure the
**Horizontal distance**between the hands and the midpoint between the ankles at the start and end of the lift. This distance is known as**H**.

(Restrictions: If**H**is less than 10, then set**H**equal to 10. If**H**is greater than 25, then the lift should be redesigned so that**H**is 25 or less.) - Measure the
**Vertical distance**of the hands from the floor at the start and end of the lift. This distance is known as**V**.

(Restrictions:**V**should be a value between 0 and 70 — the floor and the upper limit of vertical reach. If**V**is greater than 70, then the lift should be changed so that**V**is 70 or less.) - Measure the
**vertical travel Distance**from the start of the lift to the destination. This distance is known as**D**.

(Restrictions: If**D**is less than 10, then set**D**equal to 10. Since the upper limit of the lift is 70,**D**should also be less than 70.) - Estimate the
**Angle of twist**of the body in degrees measured at the beginning and end of the lift. This angle is known as**A**.

(Restrictions:**A**should be a value between 0° and 135°. If**A**is greater than 135°, then the lift should be redesigned so that**A**is 135° or less.) - Count the average
**Frequency of lifts**per minute. Additionally, determine the duration of lifting (<1 hrs/shift, < 2 hrs/shift, or < 8 hrs/shift). Refer to the Frequency Table to determine the frequency multiplier, known as**F**.

(Restrictions: If**F**is less frequent than once per 5 minutes (.2 lifts/min.), then set**F**equal to .2 lifts/min.) - Evaluate the hand-to-container
**Coupling**used during the lift. Refer to the Coupling Table to determine the coupling classification, known as**C**. - Enter the values into the following formula to calculate the
**Recommended Weight Limit (RWL)**.Note: If the lift requires controlling the load at the destination, then measure both origin and destination values for**H**,**D**, and**A**. Use the greater of the two values.

- Calculate the
**Lifting Index**:

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:

*Handle*: 0.75 – 1.5-inch diameter, >4.5-inch length, 2‑inch clearance, cylindrical shape, and a smooth, non-slip surface*Handhold*: >3-inch height (plus above length, clearance, and characteristics)*Container*: <16-inch frontal length, <12-inch height, and a smooth non-slip surface

*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:

- held directly against the body
- at about waist height
- no vertical movement
- infrequent
- no twisting
- easy to hold
- short duration of lift

**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.