Strain Index — SI

Overview

The Strain Index is an ergonomic risk assessment method used to evaluate the risk of distal upper extremity musculoskeletal disorders from work requiring repetitive and forceful exertions of the hand and wrist. The tool assesses six task variables — intensity of exertion, duration of exertion per cycle, exertions per minute, hand and wrist posture, speed of work, and duration of task per day — each assigned a multiplier based on defined criteria, and combines the multipliers into a composite Strain Index score. A score below three is generally considered safe, three to five questionable, and above seven ha zardous — providing a clear risk classification that guides intervention. The Revised Strain Index — RSI — is an updated version with improved validity.