2007, Piran, Slovenia

Acute and chronic heat exposure
30%) separated by a period of passive heating in a sauna. The sauna was maintained at 68
(3)°C (relative humidity < 30%) and subjects remained in the sauna until ΔTcore = 2°C or for a
maximum of 90 minutes. During one visit, subjects had their head and face cooled continually
during the sauna (HC) by indirectly applying ice-packs to the head and spraying the face with
cold water, whilst the other visit acted as a control (CON). Rectal and skin temperatures as
well as heart rate were recorded continually, with RPE and subjective TC taken at regular
intervals. A randomised cross over design was used to minimize any order effects, subjects
completed trials at the same time of day to minimize any influence of circadian variation and
trials were at least 7 days apart to minimize any acclimation effects. Statistical analyses were
conducted using repeated-measures ANOVAs and Student’s paired t-tests, with a Bonferroni
correction where appropriate. All data are presented as mean ± S.D.
The design of the present study allowed two hypotheses to be tested:
1. Passively increasing Tcore would negatively influence capacity and perception during
exercise in the heat (EX1CON vs. EX2CON).
2. Head-cooling during passive heating would attenuate the unpleasant sensations of an
increased Tcore (EX2CON vs. EX2HC).
Figure 1. Design of the study protocol in diagrammatic form.
RESULTS
Effect of Passive Heating
The effects of passive heating on exercise are displayed in Table 1. Passive heating increased
Tcore by 1.6 ± 0.5°C from the start of EX1 to EX2. This resulted in exercise time being
significantly reduced (8.1 ± 4.1 min; p < 0.05), with only 4 subjects able to complete EX2
compared to all 9 subjects completing EX1. Passive heating also increased Tsk and heart rate
during exercise, as well as negatively influencing both RPE and TC.
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