ARTICLE: PART 1- Separate and combined effects of dehydration and thirst sensation on exercise performance in the heat



One key ergogenic aid proposed for maintaining or
enhancing endurance exercise performance in the heat
has been maintaining adequate hydration (Sawka et al.,
2007; Cheuvront & Kenefick, 2014), and fluid replace-
ment may exert benefit through either allaying thirst or
through decreasing physiologic strain. The physical act
of drinking modifies an individual’s perception of thirst
(Figaro & Mack, 1997). Thirst plays an integral role in
the body’s homeostatic mechanism for fluid levels by
acting as one of the key psychologic indicators to replen-
ish lost fluids (McKinley, 2004), and can potentially
influence the motivation for exercise. Specifically, thirst
can be modulated by decreasing exercise intensity to
prevent further fluid loss (Sawka & Noakes, 2007), such
that impaired exercise performance in dehydrated sub-
jects may be closely linked to the perception of thirst. In
support, a meta-analysis by Goulet (2011) showed that
time trial (TT) performance improved when subjects
drank solely to attenuate thirst compared with drinking
to completely replenish fluid loss or to not drinking at
all. This meta-analysis further concluded that drinking
according to thirst resulted in a mean power output
increase of 5.2% compared with drinking below thirst
sensation, and 2.4% compared with drinking above thirst
sensation. Direct experimental evidence from the same
laboratory indicated that half-marathon treadmill run
speed and completion time in the heat were not different
in trained runners drinking to thirst (3.1% body mass
dehydration) or on an enforced schedule (1.3% dehydra-
tion) (Dion et al., 2013).

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