2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
Figure 1: Exercise protocol
The exercise protocol was 10 min sitting rest, followed by 30 min walking on a
treadmill at a speed of 5.8km/h, and then 30 min seated recovery. A whole procedure
lasted 70 min. The experiments were carried out in two time periods each day:
morning and afternoon. The six participants were thus divided into two groups: AM
group and PM group; and wore SC and C T-shirts respectively on different days. They
were asked to rest in the chamber for about 30 min to be adapted to the environment
before the experiment started. The temperature (Tcl) and the relative humidity (P) of
the microclimate under the T-shirt at the back, where more sweat glands exist, were
recorded each minute.
RESULTS
The results of fabric tests are shown in Figure 2. As expected, the SC fabric was
superior in moisture transfer (wicking), while the C fabric had better water absorbing
properties.
Mass of wat er
absor bed( g)
154
8
7.5
7
6.5
6
5.5
5
SC C
Samples
Hei ght of wat er
r i se( mm)
(a) Static immersion (b) Wicking
Figure 2: Fabric tests
50
40
30
20
10
0
SC C
Samples
Figure 3 shows the change of Tcl and P over time for the two groups of participants.
During the resting period, the P kept stable. When the participants started to walk (10
min), additional body heat was generated and the body temperature increased.
However, the P did not increase immediately. As the temperature exceeded a value of
the threshold temperature for the body to sweat, P began to increase. Therefore, there
was an obvious delay (>10 min) for the body to begin sweating. When the participants
stopped walking (40 min), P did not decrease immediately. During the recovering
period, as the accumulated sweat was being absorbed by the T-shirt and then
evaporated to the external environment, P decreased gradually to its initial values.
During the resting period, the Tcl of most participants did not show a big change. As
the participants began to sweat, and with sweat evaporation extracting heat, the Tcl
decreased significantly. Finally, as P recovered, the Tcl began to increase again.
The change of Tcl and P showed great variability among individuals in terms of time
starting to sweat, peak P reached (corresponding to total sweat loss), and the width of
wale
course