Jaideep Godara

Physical & Mental Workload Assessment (2006)

Organization: Human Factors engineering and ergonomics center, Virginia Tech
Duration: 3 months

Introduction:
This project was a part of another long-term project; my responsibilities included observing the routine tasks of various workers in a postal company, and then doing a series of mental and physical workload assessment. These assessment studies aimed to study these tasks to see if the workload is within safety measures and optimum for long-term efficiency and productivity.

Physical Workload assessment:
After initial work observation and task analysis for different routine tasks, I identified the potentially problem areas on the following aspects (NIOSH Work practices Guidelines):

• Postural stress
• Forceful exertions
• Repetitive exertions
• Sustained (static) exertions
• Localized mechanical (contact) stresses
• Vibration

Further, I evaluated all the sub-tasks for a given job on the afore-mentioned parameters and documented initial ratings to identify problematic sub-tasks.
Once a particular task identified as potential risk factor, I used a combination of static and dynamic testing to measure muscle fatigue, strength levels etc. The methods used for these measurements included Goniometers, EMG and psychophysical strength measurement.

Mental Workload assessment:
The mental workload assessment primarily focused on various monitoring and decision making tasks for example a task where worker simultaneously monitors interfaces on weighing, scanning instruments in company warehouse

I used the combination of modified Cooper-Harper workload scale and Sender's approach to evaluate the mental workload. The aspects that I included in workload assessment included:

• Number of instruments
• Bandwidths of the respective instruments
• Operators' information processing rates
• The graphs of pointer behavior of the instruments and transition times

The following is a graph showing pointer behaviors for the two instruments studied

The Graph of Instrument Pointer Behavior Used to Calculate Mental Workload

Deliverables:

• Documentation of identified risk factors and risk levels for the job positions
• Documentation of capable population percentage for the potentially risky tasks
• Guidelines for the improvement in the identified risk prone tasks

The following images show the parts of this job evaluation process to determine physical workload

Motion measurement during a box lowering task using Optoelectronic systems

Force distribution on hands for the box lowering task

A lower arm free-body diagram used for the Static exertion evaluation

Documentation table to show capable population percentage for a static exertion task