2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
RESULTS
HOT study (n = 11): Three trials were conducted, one at 22°C (CONTROL) and two
at 29°C [hydrated (HYD) and dehydrated (DYD)], whereby subjects wore a vapourimpermeable
protective garment while walking on a treadmill at 3 km⋅h -1 every 25
min per half hour for up to 4 h. In addition, water at 42°C was circulated through a
tube suit worn underneath the clothing during the hot condition. Figure 1 shows the
resultant core temperature and heart rate responses, neither of which was different
between HYD and DYD.
Figure. 1. Mean ± SE of core temperature (a) and heart rate (b) against time.
Subjects engaged 24 foe and 12 friendly targets during 15 min every half hour.
Despite significant phsysiological strain, neither trial nor time on task degraded the
subjects’ performance. Target detection time, engagement time, and hit accuracy
consistently averaged about 1.2 s, 4.7 s, and 75%, respectively, across all trials.
COLD study (n = 12): Two trials were conducted, one at 22°C and the other at 0°C
(COLD). Water at 5°C, during COLD only, was circulated through a tube suit worn
on top of the t-shirt and shorts by the subjects. They were challenged by two separate
scenarios, one that involved engaging 60 frequently appearing targets in an urban
scene lasting 15 min and held at the beginning, mid-point, and end of the trial, and the
other involving two 1 h sentry duty sessions of detection and identification of 12
targets in a mountainous terrain conducted before and after the mid urban session.
Significant cold strain developed during COLD (core, finger, hand, forearm, and
upper arm temperatures reached 36.3 ± 0.7, 10.8 ± 1.9, 17.5 ± 3.8, 22.4 ± 2.3, and
23.0 ± 3.1ºC, respectively, by the end of the trial), yet without any degradation in
performance. Although core and skin temperatures evoked a noticeable shivering
response, marksmanship was largely unaffected, which can be attributed to a
conscious suppression of shivering tremor given that engagement times were brief (~
4 s), as previously found under milder conditions.
NOISE study (n = 20): The single trial described herein followed a familarization
trial, whereby subjects were exposed to alternating 30 min bouts of relative quiet (<
54 dBA) and battlefield noise of 87 dBA while walking and engaging targets as
described in the HOT study above. The detection of targets was unaffected by noise
and time, and averaged 96.3%. However, the detection times of friendly targets were
longer under noise (by 0.06 s) compared to the quiet condition. Time on task affected
target detection, identification, and engagement, whereby the detection of friendly
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