NIOSH Lifting Equation - Applicability Guidelines
As per WHO (World Health Organization), "low back pain" is single leading cause of disability in 160 countries (1).
National Institute for Occupational Safety and Health (NIOSH) recognized the growing problem of work-related back injuries and published the Work Practices Guide for Manual Lifting (NIOSH WPG, 1981). The 1991 revised lifting equation reflects new findings and provides methods for evaluating asymmetrical lifting tasks, lifts of objects with less than optimal hand-container couplings, and also provides guidelines for a larger range of work durations and lifting frequencies than the
1981 equation.
However, Revised NIOSH Lifting Equation (NLE) is not applicable for every lifting task in every condition. The limitations need to be considered while applying them.
Lifting Equation is not applicable in following conditions:
- Lifting/lowering with one hand
- Lifting/lowering for over 8 hours
- Lifting/lowering while seated or kneeling
- Lifting/lowering in a restricted work space
- Lifting/lowering unstable objects
- Lifting/lowering while carrying, pushing or pulling
- Lifting/lowering with wheelbarrows or shovels
- Lifting/lowering with high speed motion (faster than about 30 inches/second)
- Lifting/lowering with unreasonable foot/floor coupling (<0.4 coefficient of friction between the sole and the floor )
- Lifting/lowering in an unfavorable environment (i.e., temperature significantly out-side 66–79° F (19–26° C) range; relative humidity outside 35–50% range)
When the revised lifting equation is not suitable for lifting tasks, it may be necessary to conduct a more comprehensive ergonomic evaluation. This evaluation would aim to quantify other physical stressors, such as prolonged or frequent non-neutral back postures or seated postures, cyclic loading (such as whole body vibration), and unfavorable environmental factors like extreme heat, cold, or humidity. These factors can contribute to the overall risk of musculoskeletal disorders (MSDs) or other adverse health effects.
References:
- https://www.who.int/news-room/fact-sheets/detail/musculoskeletal-conditions
- Revised NIOSH Equation for the Design and Evaluation of Manual Lifting Tasks, by Waters, Putz-Anderson, Garg, and Fine, 1993
- Applications Manual for the REVISED NIOSH LIFTING EQUATION by Waters, Putz-Anderson, and Garg, 1993
