Trades workers often complete many different tasks, at varying frequencies, and with differing postures and forces for each task during their day.  It is therefore difficult to use the typical ergonomic assessment tools to evaluate the risk of injury over the course of an 8-hour work day. 

Completing a physical demands analysis (PDA), or physical demands description (PDD) of the job (breaking down the individual tasks of the whole job), will help you to gain an understanding of tasks and frequencies completed by the worker.  You can then determine if a typical ergonomic assessment tool (NIOSH, Snook, Mital, etc.) is valid to use.  

If the overall job cannot be assessed using the typical Ergonomic assessment tools due to frequency, awkward postures or duration, there are other factors to investigate in order to reduce the risk of injury.  These include:

·         assess the individual tasks
·         assess the work tools being used
·         assess for acceptable clearance and/or access points to machinery
·         evaluate for a one time maximum exertion to determine risk of injury
·         develop guidelines for maximum weight of lifting
·         assess the need for personal protective equipment (PPE)
·         obtain feedback from the employees themselves 

Assess the individual tasks - Identify the specific tasks and the frequency at which they are completed.  From there, if the task is completed at a fairly frequent repetition, then use the appropriate analysis tools (NIOSH, Snook tables, Mital, etc).  If they are completed at low frequency but with high force, use a biomechanical assessment tool (i.e. Univeristy of Michigan 3D Static Strength Prediction Program (U of M product) or JACK 6.0 or 7.0 (UGS/Siemens product)). 

Assess the tools being used - Tools used by a trade worker can range from a simple screwdriver to a large jack hammer.  Ensuring the designs of tools are ergonomically acceptable will reduce the likelihood of injury.  Hand-arm vibration related injuries can be a common injury among Trades workers as well.  Quantifying the level of tool vibration is a good way to determine the potential risk of injury.  ACGIH has developed a Threshold limit value (TLV), see link below.  

Access clearance - Trades workers may be asked to enter very tight spaces, whether it is with the full body, or just hands and/or arms to complete tasks.  Humanscale has excellent information on clearances for all types of anthropometrics (see reference and link below).  JACK 7.0 (UGS/Siemens product) also has the ability to provide dimensions of human segment lengths and girths. 

One time maximum strength analysis using biomechanical models - Strength for infrequent tasks can be analyzed using biomechanical software such as JACK 7.0 or University of Michigan 3 Dimensional Static Strength Program. These software programs have the ability to move a three-dimensional manikin into any posture and then determine the maximum acceptable weight of the load in the hands.  It may be possible to use the revised NIOSH lifting equation, however this tool assumes a symmetrical lift, and trades workers are often lifting items requiring the use of an asymmetrical posture.  Also, the frequency of these lifts could be very low, which makes NIOSH not applicable.  Hence, biomechanical analyses could be used to assess the risk.   

Maximum lifting guidelines – Some companies have established a maximum acceptable weight limit for any manual lift.  For example, lifting guidelines for company X state, ‘no employee will manually lift more than 35lbs’.    

Personal Protective Equipment (PPE) - Depending on the awkward postures assumed by the employee, knee pads, kneeling mats, elbow pads, anti-vibration gloves, grip enhancing gloves, push carts, etc., could be used/classified as PPE to ensure an ergonomically safe task/operation can be completed by an employee. Ask employees - Which task(s) does the employee find the most physically demanding, leads to discomfort, etc.?  Analyze this particular task, identify the risk factors, and attempt to reduce/eliminate the risk factors. 

The seven points above provide opportunities to analyze and reduce the risk of injury for Trades workers. If you would like to read more about these methodologies you may wish to visit the links below.

.

References

Proper hand tool design and usage:http://www.ccohs.ca/oshanswers/ergonomics/handtools/tooldesign.html

American Conference of Governmental Industrial Hygienists – Human Response to Vibration: http://www.acgih.org/Store/ProductDetail.cfm?id=1802

Henry Dreyfuss Associates (1991). Humanscale. Cambridge, MA.  Massachusetts Institute of Technology Press. http://www.hda.net/