initial body weight through sweating without replacing
the lost fluid is at risk of heat cramps, heat exhaustion,
and heat stroke. Moreover, dehydration may be pro-
gressive in athletes who do not replace fluid loss over-
night; the greater the loss of body fluid, the longer it
takes to rehydrate the body. When dehydration has
taken place over 2 to 3 days, it will take a minimum of
48 hours to replace the fluids in body tissues. The health
risks of dehydration are a major reason why abuse of
diureticsis dangerous in athletes.
People vary in their sweating rates; therefore,
health professionals must evaluate athletes on an indi-
vidual basis to determine how much fluid is needed
after exercise or training. The most common way to
measure this need is to weigh the athlete before and
after exercise; the amount of weight lost should be
replaced with an equal amount of fluid before the
next workout. The usual rule of thumb is 1 pint of
fluid containingcarbohydratesandelectrolytesfor
each pound of weight loss.
Good hydration is more effectively maintained by
consuming sports drinks or other beverages that con-
tain salt and carbohydrates than by drinking plain
water. Sports drinks are isotonic; that is, they contain
the same proportion of electrolytes and carbohydrates
to fluid as the human body. After exercise, the body
requires carbohydrates to replace the glycogen (a com-
plex sugar) stored in muscle tissue and the liver. Gly-
cogen is an important source of reserve energy for
muscles; long-distance runners who deplete their
stores of glycogen may experience fatigue to the
point of being unable to move. In addition to the riskKEY TERMS
Amenorrhea—Absence or suppression of normal
menstrual periods in women of childbearing age,
usually defined as three to six missed periods.
Bioelectrical impedance analysis (BIA)—A techni-
que for evaluating body composition by passing a
small amount of electrical current through the body
and measuring the resistance of different types of tissue.
Body dysmorphic disorder—A mental disorder
involving extreme preoccupation with some feature
of one’s appearance. Excessive time spent in phys-
ical exercise, often involving bodybuilding or
weight-lifting practices, is a common symptom of
the disorder in adolescents.
Creatine—An organic acid formed and stored in the
body that supplies energy to muscle cells. Meat and
fish are good dietary sources of creatine.
Doping—The use of performance-enhancing drugs in
sports competition, including anabolic steroids and
other substances banned by most international sports
organizations. The English word is thought to come
from the Dutchdop, which was the name of an alco-
holic beverage drunk by Zulu warriors before a battle.
Electrolyte—Any of several chemicals dissolved in
blood and other body fluids that are capable of con-
ducting an electric current. The most important elec-
trolytes in humans and other animals are sodium,
potassium, calcium, magnesium, chloride, phos-
phate, and hydrogen carbonate.
Ergogenic—Enhancing physical performance, par-
ticularly during athletic activity.Erythropoetin (EPO)—A hormone produced by the
kidneys that regulates the production of red blood
cells. It is sometimes used by athletes to increase the
oxygen-carrying capacity of their blood.
Female athlete triad—A group of three disorders
often found together in female athletes, consisting of
disordered eating, amenorrhea, and osteoporosis.
Glycogen—A complex sugar that is the primary form
in which glucose is stored in muscle and liver tissue.
Purging—A behavior associated with eating disor-
ders that includes self-induced vomiting and abuse
of laxatives as well as diuretics.
Sports drink—Any beverage containing carbohy-
drates, electrolytes, and other nutrients as well as
water, intended to help athletes rehydrate after train-
ing or competition. Sports drinks are isotonic, which
means that they contain the same proportion of
water, electrolytes, and carbohydrates as the
human body.
Vegan—A vegetarian who excludes all animal prod-
ucts from the diet, including those that can be
obtained without killing the animal. Vegans are
also known as strict vegetarians.
Water intoxication—A potentially fatal condition
that occurs when an athlete loses sodium from the
body through perspiration and drinks a large quan-
tity of water in a short period of time without replac-
ing the sodium. Long-distance runners are
particularly susceptible to water intoxication.Sports nutrition