Q: What is the Strain Index?
A: The Strain Index is a tool used to evaluate a job’s level of risk for developing a disorder of the hand, wrist, forearm, or elbow. The analyst evaluates six task variables (intensity of exertion, duration of exertion, exertions per minute, hand/wrist posture, speed of work, and duration of task per day). The task variable is given a value called a multiplier. The product of the six task variable multipliers produces a number called the Strain Index score. This score is compared to a gradient that identifies level of task risk.
The original reference for the tool is: J. Steven Moore and Arun Garg, “The Strain Index: A Proposed Method To Analyze Jobs For Risk Of Distal Upper Extremity Disorders”, American Industrial Hygiene Association Journal, 56:443-458 (1995).
Q: When is this tool applicable?
A: The Strain Index is an appropriate tool to use when you need to evaluate the risk of developing a musculoskeletal disorder (MSD) in a hand intensive task. Many small assembly tasks will qualify for this.
Q: What are some limitations of the Strain Index?
A: The authors have outlined the following limitations of this tool:
Q: Has there been any additional research on the Strain Index since the original publication?
Q: What is the output of this tool?
A: Once the six task variables have been defined for the task being evaluated and the appropriate multiplier derived, the multipliers are multiplied to give the Strain Index score (SI score).
SI Score = (Intensity of Exertion Multiplier) * (Duration of Exertion Multiplier) * (Exertions per Minute Multiplier) * (Posture Multiplier) * (Speed of Work Multiplier) * (Duration per Day Multiplier).
It was found that jobs associated with distal upper extremity disorders had scores greater than 5.
For more information and assistance with the Strain Index, consider these Ergoweb resources, from which portions of this article were taken: