2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
measured every 5 minutes using a Thermal Sensation Scale (range 0 = unbearably cold to 10
= unbearably hot in 1 unit increments).
Following baseline, participants donned the cooling hood and rested quietly in a chair in a
thermoneutral environment (23°C, 40%RH) for 60 min. The cooling hood was then removed
and a further 10 min of data were collected to investigate the afterdrop of rectal temperature.
No Cooling: the hood was not turned on. True Cooling: the circulating cooling fluid was set at
10°C. Sham Cooling: the goal of the Sham Cooling condition was to give the perception of
cooling while minimal physiological changes occurred. To ensure that participants felt they
were receiving a cold stimulus, upon donning the cooling device the circulating cooling fluid
was set at ~10°C. After 5 min of cooling, the cooling fluid temperature was increased until it
reached ~24°C. After 30 min, the cooling fluid was briefly decreased to ~10°C and was then
increased to ~24°C. This cyclic change in the temperature of the cooling fluid was performed
again at 55 min so that participants felt a chill before they took the cooling hood off.
RESULTS
Upon donning the cooling hood, both the Sham and True Cooling groups experienced a slight
increase in core temperature (Figure 1). However after 5 min, core temperature steadily
decreased in the True Cooling condition, decreasing by 0.37 o C (p0.05). The magnitude
of cooling was significantly greater in True compared to either Sham or No Cooling (p=0.05).
Although core temperature in the True Cooling condition was significantly different from the
Sham and No Cooling conditions, there were no significant differences between the thermal
sensations that participants experienced between and within all conditions (Figure 2).
However, it is worth noting that there is a trend for both the Sham and True Cooling to elicit
lower ratings of thermal sensation than the No Cooling condition.
414
Delta T Rectal
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5
-0.6
0 10 20
Time (min)
30 40 50 60 70
True Cooling
Sham Cooling
No Cooling
Figure 1. Change in rectal temperature over 60 min with cooling hood (dashed vertical line) plus
10 min additional passive rest without hood. * = core temperature significantly different from
time 0 min to time 60 min and 70 min for True Cooling condition only (p