Dont Overdo Strenuous Activity in Hot Humid Weather

Heli J. Roy  |  3/29/2005 11:25:18 PM

The combination of heat, humidity and hard work can spell trouble for people cleaning up after a disaster, especially if they don't usually work outdoors. We usually think of dehydration happening to athletes engaged in sports activities, but it can also affect farm workers, construction workers, gardeners and anyone not used to working in the hot outdoors for an extended period.

High humidity aggravates the problem, since it reduces the efficiency of sweating. Sweating is how our bodies attempt to cool down; when the air is full of water (high humidity), sweat doesn’t evaporate.


Signs of Dehydration

Dehydration can start before we get thirsty. Increased thirst is a response to a loss of body water, but to stay hydrated, we need to start replacing lost fluids before first signs of thirst. A good sign of proper hydration is the output of large volumes of clear, dilute urine. These are some signs of dehydration in various stages:

  • Mild dehydration: increased thirst, headache, dry lips and discomfort.
  • Moderate dehydration: nausea, sunken eyes, increased body temperature, difficulty in concentrating, irritability.
  • Severe dehydration: weakness, mental confusion, rapid and weak pulse (more than 100 at rest), cold hands and feet, rapid breathing, blue lips, confusion, dizziness, increased body temperature, lethargy and muscle spasms. Decreased sweating.
  • Dehydration is accompanied by weight loss.


Preventing Dehydration

  • Drink before, during and after being outdoors. Hydrate thoroughly the day before if you can. Try to consume 4 to 8 fluid ounces of water every 15 to 30 minutes during heavy activity in hot climates. Although the temperature of the replacement fluid is not critical, fluids at room temperature may replace lost fluid in cells faster than chilled fluids. Plain water or electrolyte solutions are good choices. Avoid caffeine and alcohol; these are diuretics and cause your body to lose water. Most of the dark soft drinks contain caffeine.
  • Hyperhydrate just before going out. Drinking 1½ to 3 cups of cold water or an electrolyte solution can help delay the process of dehydration.
  • Dress in light-colored fabrics that breathe. When outdoors, wear light-colored clothing that reflects light and that is of loose, lightweight material. Tightly woven clothing does not allow heat to pass through. Some synthetic clothing made today is designed to allow sweat and heat to be pulled from the skin.
  • Wear a wide-brimmed hat. To keep sun away from the face and head, wear a hat, preferably one that allows air to circulate, such as one made from cotton or straw.
  • Check with your doctor about the medications you are taking. Antihistamines and some blood pressure medications decrease sweating. Since these and other drugs may cause dehydration or interfere with cooling, check with your doctor to see if you can avoid their use for several days before being outdoors doing physical labor or if you should avoid being outside in the heat.

It is possible to adapt to the heat through a process called heat acclimatization, where the body makes adjustments to promote better cooling in hot environments. Sweat becomes more dilute, and your body learns to hold on to salt. The threshold at which sweating begins is lowered, and the sweat rate is increased. These changes take time to complete fully -- about 10 days of high activity in the heat -- and will work only if you are well hydrated.

Dehdyration can be brought about in other situations. It can occur during illness when there is severe vomiting and diarrhea, and it may be caused by diabetes, kidney disease, excessive use of diuretics, liver disease resulting in accumulation of fluid in the abdominal cavity, inflammation of the abdominal cavity resulting in fluid accumulation and burns. People who are predisposed to dehydration should not expose themselves to greater risk by doing physical labor outdoors in the heat.

When you are outdoors in a hot environment, make sure to carry water with you and drink every few minutes, even when you don't feel thirsty. You can prevent dehydration that way.

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