Nutritional Needs in Hot Environments Applications for Military Personnel in Field Operations (1993) / Chapter Skim
Currently Skimming:
5. Water Requirements During Excercise in the Heat
5. Water Requirements During Excercise in the Heat
Pages 87-96
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 87... ...
The effects of dehydration occur with as little water loss as 1 percent of body weight and become life threatening at 10 percent (Adolph et al., 1947~. Humans cannot adapt to a chronic water deficit, so fluid losses must be replaced if physiological function is to continue unimpaired.
|
From page 88... ...
DISTRIBUTION OF BODY WATER Total body water constitutes about 70 percent of lean body mass and is most simply divided into two major compartments: (a) intracellular water, which represents 50 percent of body weight or 35 liters in a 70-kg man, and (b)
|
From page 89... ...
Urine volume is usually 700 ml per day, but a high-protein diet demands more obligatory water to excrete the osmotically active products of protein metabolism. DETERMINANTS OF SWEAT RATE Water requirements during exercise in the heat primarily depend on evaporative cooling.
|
From page 90... ...
~ I_ . ok ~ ~ ~ fL First Second Hour Hour 1 Third Fourth Hour Hour ,~ : Fifth Sixth Seventh Hour Hour Hour 8 Hours FIGURE 5-1 Rectal temperatures, heart rates, metabolic rates, and weight losses of four highly trained endurance runners during mild treadmill exercise in dry heat, in wet heat, and in a cool ambient temperature.
|
From page 91... ...
Heat Acclimatization Maximal sweating capacity can rise from 1.5 liters per hour in a healthy unacclimatized man to as much as 2 to 3 liters per hour in a highly trained acclimatized soldier (Wenger, 19881. One of the highest sweat rates ever observed was recorded on Alberto Salazar during the 1984 Olympic Marathon.
|
From page 92... ...
Prediction of Water Requirements Sweat rate can be predicted from a measure of the overall heat load (Ereq) and the maximal evaporative cooling capacity of the environment (EmaX)
|
From page 93... ...
Naman, and F Sargent II 1967 Sex differences in physiological reactions to thermal stress.
|
From page 94... ...
DR. GISOLFI: Body fat is going to impede heat loss, certainly, and if you evaluate the impact of body weight to surface area ratio, the heavier person has a greater metabolic heat load and has a smaller surface area to dissipate that heat.
|
From page 95... ...
If you are dealing with a relatively fit individual that you then heat acclimatize, you probably see little change in the sweating response. If you are dealing with people who are terribly unfit and you heat acclimatize them, you will see a rather substantial elevation in the sweating response.
|
From page 96... ...
So if you heat acclimatize a soldier, you will observe increases in sweating early in the process. However, at the end of acclimatization, if you are looking at just total body sweating, you are actually looking at a small rise in body temperature and the same sweating response.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.