2007, Piran, Slovenia

Sweating
Table 1: Sweat gland counts (glands.cm -2 ) from European and Asian population samples.
Region Thompson (1954) Szabo (1962) Hwang and Baik (1997)
Forehead 215 360 ---
Chest 81 175 86
Back 88 160 96
Arm 111 150 98
Forearm 114 225 96
Thigh 86 120 118
Leg 87 150 104
Dorsal foot 194 250 144
Resting sweat rates: It is generally recognised that, in heated resting subjects, sweating
commences caudally, with recruitment at rostral areas commencing later (Hertzman et al.,
1953). There is even evidence for a dermatomal recruitment pattern (Randall and Hertzman,
1953). Following the establishment steady-state sweating, the forehead is known to secrete
the most sweat, with lower sweat rates being reported for the arms (Hertzman et al., 1953),
hands (Weiner, 1945) and chest (Park and Tamura, 1992), with considerable variability
among individuals. However, data pertaining to the distribution of sweating are far from
complete, with most investigators studying a limited number of sites. Accordingly, we have
very recently completed a more exhaustive series of projects, in which the local sweat rates of
>50 sites were measured during rest, whilst subjects were passively heated. These data will be
described in other presentations at this conference.
Exercising states: We have previously shown that, during exercise, sweat recruitment patterns
differ from those observed at rest (Cotter et al., 1995), with equivalent core temperature onset
thresholds being evident among regions. Whilst all local sweat rates increase during exercise,
inter-regional differences are still clearly evident, with the forehead and scapula consistently
sweating more, and the chest, upper arm and thigh having less prolific secretion. More
recently, we have extended these data to include steady-state and peak sweat rates in subjects
exposed to combined exercise and passive thermal loading (core temperature >39 o C). Data
were collected from >40 sites, and these will also be described at this conference.
Heat acclimation: Short-term heat adaptation does not alter the number of active sweat glands
(Inoue et al., 1999), however, it does elicit a greater glandular flow during subsequent
exposures, and this adaptation is consistently observed across ethnic groups (Taylor, 2006).
Höfler (1968) reported heat acclimation to induce a peripheral redistribution of sweating, such
that post-acclimation limb sweat rates appeared to be elevated more than at central body sites.
Whilst data from several laboratories, including our own, are consistent with such a sweat
redistribution, methodological limitations within these experiments may invalidate such an
interpretation. In fact, when these limitations were addressed, we found that, while all limb
skin regions increase secretion following humid-heat acclimation, only the forearm showed a
greater elevation in sweat rate than the central sites (Patterson et al., 2004). The mechanism
for these local adaptation variations may be related to differences in pre-experimental sweat
gland capacity. During heat acclimation, glandular flow increases such that the inter-site
variation in glandular capacities is reduced. We hypothesised that skin regions further away
from their site-specific maximal glandular capacity (e.g. the forearm) will undergo the
greatest increase in secretion (Patterson et al., 2004). Such increases do not represent a
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