Fun in the Sun Means Proper Preparation
WebMD News Archive
Of course, there is a way around all this: water. It's important for
everyone, but it takes on added importance for people working outside, whether
they are paving roads or exercising.
David Martin has completed 29 marathons, and he's never, as he calls it,
"bonked." But plenty of athletes, experienced or not, fade as they work
out in temperatures high enough to make a kettle whistle.
Martin says he owes his successful track record to proper preparation --
especially the proper regulation of fluids. Of course, he also has an advantage
over most people in that he has a PhD in physiology and is the chairman of
sport science for U.S.A. Track and Field.
"I've always been sly enough and followed my principles of
physiology," Martin tells WebMD. Those principles are quite simple, he
says: If you're an athlete -- whether you're training for the Olympics or just
jogging around the block -- "you really want to live a healthy lifestyle,
which means not being thirsty and not being hungry."
Although avoiding the hottest parts of the day is best, that's not always
possible. So week-long laborers and weekend warriors alike should make sure
they never let themselves get thirsty.
"As soon as they have reached a point of thirst, they actually are
dehydrated," Martin tells WebMD. "We say you never pass up a drinking
fountain, or carry a small bottle and take sips to make sure your fluid levels
The most dangerous condition for exercisers, Martin says, is humid heat. The
evaporation of sweat helps to cool the body, but humidity limits the amount of
evaporation, he explains.
If you're exercising, that can be critical. Most of the perspiration we
produce comes from blood plasma. So excessive perspiration can decrease the
volume of blood just when it is needed in the muscles that are working.
In times of heat stress, the body also sends blood to the skin surface to
cool the body by radiant heat loss. "But at the same time, you want that
same amount of blood to go into your working muscles, so that you can provide
nutrition and oxygen for metabolism. And if you have to share a smaller and
smaller amount of blood, because of sweating, with these two major tissue
masses -- the skin for cooling, but the muscles for working -- something has to
give," Martin says.
This could hurt the athlete's performance, or it could lead to heat
exhaustion or even heat stress. A person racing in the heat, for instance, can
lose a liter to a liter and a half of sweat an hour. But the body can absorb
about a liter of water an hour, so adaptations are necessary for those who must
compete or work in the heat.