A Guide to Safe Ergonomics: Manual Handling of Loads
How to use the NIOSH method to reduce back injuries in the workplace.
Why do we measure ergonomic risk?
Musculoskeletal disorders (most commonly lower back pain, herniated discs and joint damage) are a leading cause of sick leave and occupational diseases in industry, logistics and construction.
Workers often judge a load only by its weight (kg), but spinal damage is rarely caused by heavy weight alone. Frequently repeated lifting of lighter loads from awkward positions (from the floor, above the head) or with a twisting (rotating) torso is far more dangerous.
How does the NIOSH calculator work?
The calculator takes the actual weight of your load and divides it by the Recommended Weight Limit (RWL). The RWL is calculated using 6 multipliers, each of which lowers the ideal 23 kg (51 lb) when conditions are less than ideal:
- H (Horizontal): The distance of the load from the body (the farther away, the harder the lift).
- V (Vertical): The height of the hands at the start of the lift (lifting from the floor is bad).
- D (Distance): How far the load travels up or down.
- A (Asymmetry): The angle at which the body twists.
- F (Frequency): The number of lifts per minute.
- C (Coupling): How good the grip is (e.g. handles on a box).
What should you do when the lifting index (LI) is above 1.0?
If you get a high result, you don't necessarily need to buy expensive lifting equipment. Simple organizational measures are often enough: 1) raise the pallet onto a work table so the worker doesn't have to lift from the floor (improves the V factor), 2) move the load closer to the worker (improves the H factor), 3) reduce the package size, or 4) rearrange the workstation so the worker doesn't have to twist their spine (improves the A factor).