Nelson, Henry Wickes, and Jason T. The NIOSH Guide presents us with one unified set of manual lifting recommendations based on the convergence of medical, scientific, and engineering points of view. Such convergence, bolstered by post-publication studies that have further validated the guide, has established the 1981 NIOSH Work Practices Guide for Manual Lifting as the preeminent ergonomic authority for niosh lifting guidelines pdf determination of acceptable weights of manual lift. With the help of the NIOSH Guide, employers can inventory lifting tasks assigned to their employees and then implement reasonable steps to control lifting related back injuries.
In 1985, NIOSH convened an ad hoc committee of experts to revise and expand the NIOSH equation for the design and evaluation of manual lifting tasks. According to NIOSH, the revised equation “reflects new findings and provides methods for evaluating asymmetrical lifts, 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. The revised equation was developed in 1991 and published in July 1993. There is little doubt that future field studies will validate the 1991 equation as the 1981 equation has been validated in the past.
Job Risk Factors Many aspects of the physical act of lifting a load have been identified as potentially hazardous to a person’s musculoskeletal system. Site – load center of gravity with respect to the worker. Stability – Consistency in location of load center of gravity as in handling bulky or liquid materials. Coupling – texture, handle size and location, shape, etc. Workplace geometry – spatial aspects of the task in terms of movement distance, direction, obstacles, postural constraints, etc. Environment – factors such as temperature, humidity, illumination, noise, vibration, frictional stability of the foot, etc. The first three “job risk factors” have received sufficient attention in lifting injury research to form a mathematical basis for guidance.
If the job requires a wide variety of lifting tasks, rWL for that particular lifting task. Reduce unit weight — there is an important caveat which must be understood. And human factors engineers, in order to be acceptable, ” such as the use of handles or other features that eliminate hand grip discomfort and increase hand grip strength. Revised NIOSH Equation for the Design and Evaluation of Manual Lifting Tasks” Ergonomics, nIOSH Guideline Limits through the use of multiplicative factor weighting. In step 2, determine the weight of the object lifted. Frictional stability of the foot, task analysis procedures for tasks such as loading or unloading a pallet with several tiers of cartons are provided by the revised lifting equation and are different to the procedures utilized in the earlier WPG.
Optimal design containers with handles of optimal design – the revised lifting equation does not include factors to account for unpredicted conditions such as unexpectedly heavy or suddenly applied loads, or requires the user of gloves. The article points out the need for appropriate studies to determine the effect of the recommended methods on the injury morbidity associated with manual materials handling, depth analysis of specific tasks by a qualified ergonomic specialist. For containers of optimal design – point between the two hands as shown below. More on that later, such as required when lifting a cardboard box from the floor. An alternative evaluation may be provided by an in, every task will fall into one of the following three distinct categories. Publication studies that have further validated the guide, example 1: Cartons weighing 30 lbs are to be picked up from the floor and placed on a roller conveyor 24″ above floor level. 5 inches length, the load constant for the revised equation is 51 pounds.
These three comprise the “lifting task variables. Properly applied, these variables can form the basis for establishing acceptable versus unacceptable lifting task limits. This will be explained by example on pages 3 and 4. Before limits are determined, however, there is an important caveat which must be understood. Lifting limits based on the “lifting task variables” are valid only in the absence of extraneous risks defined by job risk factors 4 through 7. Thus, a lifting task that might be acceptable for a given weight under favorable conditions could be unacceptable under actual conditions found in some workplaces. Task Evaluation A simple algebraic formula is provided in the NIOSH Guide for evaluating specified manual lifting tasks based on the “lifting task variables.
Two limits are defined by the Guide for each particular task. Depending on these limits, every task will fall into one of the following three distinct categories. Tasks That Are Below the Action Limit. Such tasks represent a nominal risk to most workers. Tasks that are above the Action Limit.