2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
Table 1. Rectal (Tcore) and skin (Tsk) temperatures, heart rate (HR), perceived exertion (RPE)
and subjective thermal comfort (TC) during exercise before (EX1CON) and after (EX2CON)
passive heating.
422
EX1CON EX2CON
START END START END
Tcore (°C) 37.5 (0.2) 37.9 (0.2) a
Tsk (°C) 31.9 (1.3) 33.5 (1.7) a
HR (bpm -1 ) 90 (13) 172 (11) a
RPE 13.0 (1.1) 15.8 (1.8) a
TC 6.7 (0.7) 7.4 (0.8) a
a - Significantly different to Start value (p < 0.05)
b - Significantly different to corresponding EX1 CON value (p < 0.05)
39.1 (0.4) b
34.8 (2.3) b
125 (14) b
18.2 (1.6) b
8.3 (1.0) b
39.2 (0.4) b
34.5 (2.7)
180 (14) ab
18.8 (1.4) b
8.2 (1.0)
Effect of Head-Cooling
The effects of passive heating with and without head-cooling on exercise are displayed in
Table 2. Head-cooling unexpectedly blunted the rise in Tcore during passive heating by
~0.4°C. This was not an intention of the study, and resulted in Tcore being lower at the start of
EX2HC when compared to EX2CON. Head-cooling had no effect on Tsk or heart rate during
exercise, but did improve both RPE and TC. Five subjects completed EX2HC, and of the
remaining subjects four out of five cycled for longer in EX2HC than during EX2CON, although
this effect was not significant (p > 0.05).
Table 2. Rectal (Tcore) and skin (Tsk) temperatures, heart rate (HR), perceived exertion (RPE)
and thermal comfort (TC) during exercise after passive heating with (EX2HC) and without
(EX2CON) head-cooling.
EX2CON EX2HC
START END START END
Tcore (°C) 39.1 ± 0.4 39.2± 0.4 38.6 ± 0.5 b
38.8 ± 0.6 a
Tsk (°C) 34.8 ± 2.3 34.5 ± 2.7 34.7 ± 1.4 34.3 ± 1.3
HR (bpm -1 ) 125 ± 14 180 ± 14 a
127 ± 14 182 ± 14 a
RPE 18.2 ± 1.6 18.8 ± 1.4 16.7 ± 1.3 b
17.7 ± 1.6 ab
TC 8.3 ± 1.0 8.2 ± 1.0 6.8 ± 1.0 b
7.4 ± 1.0 a
a - Significantly different to Start value (p < 0.05)
b - Significantly different to corresponding EX1 CON value (p < 0.05)
DISCUSSION
These results confirm that elevating Tcore by passive heating detrimentally affects exercise
capacity and perceptual responses during exercise in the heat. These results support the
suggestion that hyperthermia is a causative element of the reduced exercise capacity and
increased perception in the heat. The addition of head-cooling to passive heating attenuated
the negative impact of an increased Tcore on perceptual responses during exercise in the heat,
although no such effect was found for exercise capacity. This result is most likely due to
head-cooling blunting the rise in Tcore.