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A frequency-duty cycle equation for the ACGIH hand activity level
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  • Description:

    A new equation for predicting the hand activity level (HAL) used in the ACGIH threshold limit value® (TLV®), was based on exertion frequency (F) and percentage duty cycle (D).


    The TLV® includes a table for estimating HAL from F and D originating from data in Latko et al. (1997) and post-hoc adjustments that includes extrapolations outside of the data range.


    Multimedia video task analysis determined D for two additional jobs from Latko’s study not in the original data set, and a new non-linear regression equation was developed to better fit the data and create a more accurate table.


    The equation, HAL=6.56lnD[F1.311+3.18F1.31], generally matches the TLV® HAL lookup table, and is a substantial improvement over the linear model, particularly for F > 1.25 Hz and D > 60% jobs.


    The equation more closely fits the data and applies the TLV® using a continuous function.

    Practitioner Summary

    The original HAL lookup table is limited in resolution, omits values, and extrapolates values outside of the range of data. A new equation and table was developed to address these issues.

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  • Funding:
    R01OH007914/OH/NIOSH CDC HHS/United States
    R21OH010221/OH/NIOSH CDC HHS/United States
    UL1 TR000427/TR/NCATS NIH HHS/United States
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