The effects of heat stress on operator perceived workload in tracking
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Eight male unacclimatized subjects were selected for the present investigation. The subjects were all in excellent health and ranged in age between 25 and 35 years. Subjects performed one-dimensional horizontal compensatory tracking, the Critical Instability Tracking Task (CITT), in each of eight environmental conditions for an hour. Two levels of ambient temperature were used: 22Â°C (72Â°F) and 35Â°C (95Â°F). Two levels of relative humidity were used: 45% RH and 80% RH. The resulting Wet-bulb Globe Temperatures were 18Â°C (64Â°F) WBGT, 21Â°C (70Â°F) WBGT, 29Â°C (85Â°F) WBGT, and 34Â°C (93Â°F) WBGT. Two levels of tracking difficulty were used: easy ()Î»low = 1.0 and Î»high = 2.0) and moderate (Î»low = 1.0 and Î»high = 5.0). Prior research has demonstrated that both ambient temperature and tracking difficulty affected significantly tracking performance (root-mean-square error) and perceived workload (SWAT rating). However, in this study, hu midity did not affect either measure significantly. This might be attributable to the upper bound of humidity (80% RH) used in this research. Therefore, research needs to be done above 80% RH to examine the effects of humidity in further detail. Results also indicated that the Subjective Workload Assessment Technique (SWAT) can be used as a good indicator of the actual changes in mental workload on tracking in heat. Finally, results showed that tracking performance decrement occurred at a lower temperature (29Â°C (85Â°F) WBGT) than did the perception of significant mental workload on tracking (which occurred at 34Â°C (93Â°F) W8GT).
- Masters Theses