A hand speed – duty cycle equation for estimating the ACGIH hand activity level rating

An equation was developed for estimating hand activity level (HAL) directly from tracked root mean square (RMS) hand speed (S) and duty cycle (D). Table lookup, equation or marker-less video tracking can estimate HAL from motion/exertion frequency (F) and D. Since automatically estimating F is sometimes complex, HAL may be more readily assessed using S. Hands from 33 videos originally used for the HAL rating were tracked to estimate S, scaled relative to hand breadth (HB), and single-frame analysis was used to measure D. Since HBs were unknown, a Monte Carlo method was employed for iteratively estimating the regression coefficients from US Army anthropometry survey data. The equation: , R2 = 0.97, had a residual range ± 0.5 HAL. The S equation superiorly fits the Latko et al. (1997) data and predicted independently observed HAL values (Harris 2011) better (MSE = 0.16) than the F equation (MSE = 1.28). Practitioner Summary: An equation was developed for estimating the HAL rating for the American Conference of Government Industrial Hygienists threshold limit value® based on hand RMS speed and duty cycle. Speed is more readily evaluated from videos using semi-automatic marker-less tracking, than frequency. The speed equation predicted observed HAL values much better than the F equation.

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