As International RSI Awareness Day approaches on February 29, we reflect on the need for quantitative exposure measurement when assessing work. While upper limb posture analysis tools like RULA are widely used for surveillance in industry, some practitioners may be less familiar with exposure assessment tools like the Revised Strain Index (Garg, Moore & Kapellusch, 2016).
Seeing as they share the same acronym, we invite you to consider 2020's International RSI Awareness Day as International Revised Strain Index Day.
The Revised Strain Index (RSI) is an exposure assessment methodology based on multiplicative interactions among five task variables. The measured variables used in the RSI include:
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Intensity of Exertion
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Duration per Exertion
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Frequency of Exertion
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Hand/Wrist Posture
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Duration of Task per Day
Multipliers for these variables are derived from the measurements, for use in the formula:
RSI = IM x EM x DM x PM x HM
Where:
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IM = Intensity Multiplier
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DM = Duration Multiplier
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EM = Frequency Multiplier
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PM = Posture Multiplier
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HM = Hours Multiplier
The Revised Strain Index is consistent with the 1995 Strain Index, but improves upon it by using continuous rather than categorical multipliers, and replacing duty cycle with duration per exertion.
And to address the age-old question of - what if the worker performs different types of tasks throughout the day? - Garg, Moore and Kapellusch (2017) have developed the Composite Strain Index (COSI) and the Cumulative Strain Index (CUSI), which quantity biomechanical stressors of complex tasks and quantify exposure over an entire work shift.
These tools should be a part of any ergonomist's toolkit and for this year's International RSI Awareness Day, we invite you to tell a friend and spread the word.