2007, Piran, Slovenia
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2007, Piran, Slovenia

2007, Piran, Slovenia 2007, Piran, Slovenia

lboro.ac.uk
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Environmental Ergonomics XII Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007 separately and altogether before and after the tests. Metabolic rate was determined by measuring VO2 for 5-9 minutes between 10 th and 20 th minutes of walking on the treadmill. Thermal responses were obtained at each 10 th minute. Weight (g) 170 500 400 300 200 100 0 -100 -200 -300 Weight loss through sweating Total accumulation Evaporative water loss All data are corrected for respiratory water loss IMP10D IMP10W IMP25D IMP25W PERM10D PERM10W PERM25D PERM25W Figure 1. Weight change through sweating, accumulation and evaporation. RESULTS AND DISCUSSION Energy production was 168±19 W/m 2 . In wet tests the metabolic rate was in average 8 W/m 2 higher than in dry tests. It may be related to higher friction in clothes, discomfort etc. Figure 1 shows weight loss through sweating, moisture gain/loss in and evaporation from the clothing system. Negative accumulation values correspond to higher evaporation than generated by sweating. As expected, accumulation was higher in impermeable coverall. Sweating was lower in cool environment and with wet underwear. In cool environment sweating was at about the same level for both permeable and impermeable clothing. Wet underwear lowered the sweat production at 10 °C. It reduced sweating considerably in warm environment in permeable, but not in impermeable overall coverall. All conditions with permeable overall coverall showed lower Tsk than corresponding conditions with impermeable one, and all wet conditions had lower Tsk than dry conditions. The lowest Tsk was observed in PERM10W and next lowest in IMP10W (Figure 2). Tsk in PERM10W was the lowest probably due to high evaporation, while in IMP10W mass loss was minimal (Figures 1 and 2). The highest Tsk was observed in IMP25D followed by PERM25D and IMP25W. In latter case the initial cooling power of moisture and later heat accumulation could be observed. Dry conditions at 10 °C behaved similarly. Trec kept growing in most conditions up to the end of the test. The rise (mean increase 0.3 °C/h for all conditions) just slowed down. In 2 wet conditions at +10 °C Trec stopped growing and even began decreasing in permeable overall coverall (PERM10W). However, the mean difference in ∆Trec by the end of the exposure was 0.15 °C between the warmest and the coolest condition. Thus, the observable differences in Tb were dominated by changes in Tsk. Tb kept increasing at 25 °C in impermeable overall coveralls (wet and dry). It kept only very slightly decreasing in 2 wet conditions at 10 °C. All conditions with permeable overall coverall showed lower Tb than those with impermeable one, and all wet conditions had lower Tb than dry conditions (Figure 3). The lowest Tb was observed in PERM10W and next lowest in IMP10W. The highest Tb was observed in IMP25D followed by IMP25W and PERM25D. Dry conditions at 10 °C behaved similarly. It can be seen that the evaporative cooling from wet

Clothing underwear at 25 °C in permeable clothing (PERM25W) had similar effect on heat balance/total heat losses as 15 °C lower ambient temperature of 10 °C (dry conditions, see also Tsk, Figure 2). Thermal sensation Figure 2. Thermal sensation versus mean skin temperature at the end of the exposure. Mean body temperature (°C) 4 3 2 1 0 -1 -2 -3 IMP10W PERM10W IMP10D PERM10D Figure 3. Mean body temperature. PERM25W IMP25W PERM25D IMP25D y = 0.4585x - 13.438 R 2 = 0.9836 -4 25 27 29 31 33 35 37 36 35 34 Mean skin temperature (°C) PERM10D PERM10W PERM25D PERM25W IMP10D IMP10W IMP25D IMP25W 33 0 10 20 30 40 50 60 Time (min) In all subjective responses the variation was high. Thermal sensation (scale from +4 very hot to -4 very cold) correlated well with Tsk (Figure 2), and as well with Tb. Comfort sensation (scale from 0 comfortable to -4 very-very uncomfortable) did certainly not cover only thermal comfort aspects and ranged in average from 0 to -2. It was, according to comments from subjects, influenced by other factors, such as thermistors or clothing etc., as well. Response was less uncomfortable in dry or drying out garments and worst in impermeable and wet, and warm environment. Skin wetness (from +3 very dry to -3 very wet) sensation ranged in average from 0 to -2 and tended to move from less to more wet in dry underwear conditions and from more wet to dry in wet underwear conditions. There was practically no difference in perceived exertion (Borg’s scale, from 6 no exertion to 20 maximal exertion) between any of the conditions. It started at around 9 and ranged around 10-12 in the end. The highest and the lowest metabolic rates were not reflected in perceived exertion response. Heart rates did correlate better but still poorly (R 2 =0.57). Heart rate did probably reflect also other type(s) of discomfort, e.g. thermal, that was indicated in perceived exertion, too. However, this did not affect energy consumption. In this respect all tested conditions were very similar. 171

Clothing<br />

underwear at 25 °C in permeable clothing (PERM25W) had similar effect on heat<br />

balance/total heat losses as 15 °C lower ambient temperature of 10 °C (dry conditions,<br />

see also Tsk, Figure 2).<br />

Thermal sensation<br />

Figure 2. Thermal sensation versus mean skin temperature at the end of the exposure.<br />

Mean body temperature (°C)<br />

4<br />

3<br />

2<br />

1<br />

0<br />

-1<br />

-2<br />

-3<br />

IMP10W<br />

PERM10W<br />

IMP10D PERM10D<br />

Figure 3. Mean body temperature.<br />

PERM25W<br />

IMP25W<br />

PERM25D<br />

IMP25D<br />

y = 0.4585x - 13.438<br />

R 2 = 0.9836<br />

-4<br />

25 27 29 31 33 35<br />

37<br />

36<br />

35<br />

34<br />

Mean skin temperature (°C)<br />

PERM10D PERM10W PERM25D PERM25W<br />

IMP10D IMP10W IMP25D IMP25W<br />

33<br />

0 10 20 30 40 50 60<br />

Time (min)<br />

In all subjective responses the variation was high. Thermal sensation (scale from +4<br />

very hot to -4 very cold) correlated well with Tsk (Figure 2), and as well with Tb.<br />

Comfort sensation (scale from 0 comfortable to -4 very-very uncomfortable) did<br />

certainly not cover only thermal comfort aspects and ranged in average from 0 to -2. It<br />

was, according to comments from subjects, influenced by other factors, such as<br />

thermistors or clothing etc., as well. Response was less uncomfortable in dry or drying<br />

out garments and worst in impermeable and wet, and warm environment. Skin<br />

wetness (from +3 very dry to -3 very wet) sensation ranged in average from 0 to -2<br />

and tended to move from less to more wet in dry underwear conditions and from more<br />

wet to dry in wet underwear conditions. There was practically no difference in<br />

perceived exertion (Borg’s scale, from 6 no exertion to 20 maximal exertion) between<br />

any of the conditions. It started at around 9 and ranged around 10-12 in the end. The<br />

highest and the lowest metabolic rates were not reflected in perceived exertion<br />

response. Heart rates did correlate better but still poorly (R 2 =0.57). Heart rate did<br />

probably reflect also other type(s) of discomfort, e.g. thermal, that was indicated in<br />

perceived exertion, too. However, this did not affect energy consumption. In this<br />

respect all tested conditions were very similar.<br />

171

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