There are multiple tools which can be used to assess the manual handling of material. Some of the most common methods are discussed below in no particular order.
NIOSH lifting equation The U.S.
National Institute for Occupational Safety and Health (NIOSH) is a division of the
Centers for Disease Control and Prevention (CDC) under the United States Department of Health and Human Services. NIOSH first published the NIOSH lifting equation in 1991 and went into effect July 1994. NIOSH made changes to the NIOSH lifting equation manual in 2021 which included updated graphics and tables and identified errors were corrected. The NIOSH lifting equation is a tool (now application ) that can be used by health and safety professionals to assess employees who are exposed to manual lifting or handling of materials. The NIOSH lifting equation is a mathematical calculation which calculates the Recommended Weight Limit (RWL) using a series of tables, variables, and constants. The equation for the NIOSH lifting equation is shown below RWL= LC\times HM\times VM\times DM\times AM\times FM\times CM where: • LC is a load constant of 23 kg (~51 lb) • HM is the horizontal multiplier • VM is the vertical multiplier • DM is the distance multiplier • AM is the asymmetric multiplier • FM is the frequency multiplier • CM is the coupling multiplier Using the RWL, you can also find the lifting index (LI) using the following equation: LI=(load\,weight)/RWL The lifting index can be used to identify the stresses that each lift will expose the employees. The general understanding is that as the LI increased, the higher risk the worker is exposed to. As the LI decreases, the worker is less likely to develop back related injuries. Ideally, any lifting tasks should have a lifting index of 1.0 or less. The NIOSH Revised Lifting Equation Manual can be found on the CDC's website or by clicking here.
Liberty Mutual tables Liberty Mutual Insurance has studied tasks related to manual materials handling, resulting in a comprehensive set of tables which predicts the percentages of both the male and female population that can move the weight of the object. The Liberty Mutual Risk Control Team recommends that tasks should be designed so that 75% or more of the female work force population can safely complete the task. Key components that first must be collected before using the Liberty Mutual tables are: • Total weight of object • Hand distance (distance away from the body) • Initial hand height (hand height at start of lift) • Final hand height (hand height at end of lift) • Frequency (how often is this task completed) The complete Liberty Mutual tables and their guidelines can be found at their website. Liberty Mutual Insurance also has provided calculators that will manually calculate the percentage for both the male and female populations. If the percentage is less than 75% for the female population, a redesign of the lifting plan should be created so that 75% or more of the female population can conduct the materials handling. The link to the calculator can be found here.
Rapid Entire Body Assessment The Rapid Entire Body Assessment (REBA) is a tool developed by Dr. Sue Hignett and Dr. Lynn McAtamney which was published July 1998 in the
Applied Ergonomics journal. This measurement device was designed to be a tool that health and safety professionals could use in the field to assess posture techniques in the workplace. Rather than heavily reliant on the weight of the object being lifted, Dr. Hignett and Dr. McAtamney developed this tool based on the posture of the employee lifting the weight. Using a series of mathematical calculations and a series of tables, each activity is assigned a REBA score. To calculate the REBA score, the tool separates the body parts into the two groups group A and group B. The body parts assigned to Group A are: • Neck • Trunk The body parts assigned to group B are: • Upper arms • Lower arms • Wrists Using the score of each body part posture in group A, locate the score in table A to assign a group A posture score. This score is then added to the Load or force. This sum is the score A. Using the score of each body part posture in group B, locate the score in table B to assign a group B posture score. This score is then added to the coupling score. This sum is the score B. Using score A and score B, the correct score C is assigned using table C. The score C is then added to the activity score. This sum is the REBA score. The REBA score is a numerical value between 0 and 4. A REBA score of 0 has a negligible risk level, while a REBA score 4 has a very high-risk level. The REBA score can also provide how quickly action needs to be taken for each REBA score.
Rapid Upper Limb Assessment The Rapid Upper Limb Assessment (RULA) is a tool developed by Dr. Lynn McAtamney and Professor E. Nigel Corlett which was published in 1993 in the
Applied Ergonomics journal. Very similarly to the REBA tool, this tool was designed so that health and safety professionals could assess lifting in the field. The tool is mainly focused on posture. Using a series of mathematical calculations and a series of tables, each activity is assigned a RULA score. To calculate the RULA score, the tool separates the body parts into the two groups group A and group B. The body parts assigned to group A are: • Upper arm • Lower arm • Wrist position The body parts assigned to group B are: • Neck position • Trunk position • Legs Using the score of each body part posture in group A, locate the score in table A to assign a group A posture score. This score is then added to the muscle use score and the force/load score which assigns the wrist and arm Score. Using the score of each body part posture in group B, locate the score in table B to assign a group B posture score. This score is then added to the muscle use score and force/load score which equals the neck, trunk, leg score. Using table C, locate the wrist/arm score in the Y-axis and the neck, trunk, leg score on the X-axis to determine the RULA score. The RULA score is a numerical value between 1 and 7. If the RULA score returns a 1 or 2, the posture is acceptable but if the RULA score is a 7, changes are needed. == Equipment to reduce risk of injury ==