The normal temperature of a human body is 98.6°F. The body produces large amounts of heat during vigorous activity which should be regulated to normal body temperature. There are several ways to dissipate heat. Convection is the transfer of heat through the air or another medium. Fans and the wind can facilitate the heat loss by convection which helps to regulate temperature. Conduction is the transfer of heat from a hot body to a cold body. The primary method of cooling is done through evaporation of sweat. The chemical process involved in the evaporation transfers heat from the body that can reduce the body temperature. When there is a humid condition, the effectiveness of evaporation can be reduced since the air is already saturated with moisture. So, it is difficult to regulate the body temperature when conditions are both hot and humid environments.
The rate of maximum sweat during physical activity can be 1-2 liters per hour. If the fluid is not replaced, then there is a chance of dehydration. If the dehydration is not corrected with water or other fluid-replacement drinks, it will be increasingly more difficult for the body to maintain normal body temperature. After some point, the rate of sweat decreases as the body tries to conserve its remaining water. It attempts to shunt blood to the skin to transfer excess heat to the environment directly, but it is less effective than evaporation and may cause various heat-related problems like heat stroke and hyperthermia.
One way to monitor the amount of fluid loss can be done by monitoring the color of urine. The American College of Sports Medicine says that clear(almost colorless) urine in large volume indicates that the body is hydrated and ready for activity. Dark yellow urine in small volume indicates that the body is dehydrated and needs fluid replacement.
Individuals with good fitness respond better to activity in heat than individuals with poor fitness. Regular exposure to heat conditions the body to sweat more effectively and this process of acclimatization makes the body maintain a normal temperature.
The apparent temperature is a combined value determined by both temperature and humidity. If the apparent temperature is below 90°F (32.2°C), then the exercise is safe for most of the people. When exercise is done at apparent temperature ranging from 90° to 100° F (37.7°C ), then it is a caution. And the temperature above 100°F is the danger for doing physical activities which should be done with extreme care or limited. Experienced exercisers can perform at higher apparent temperatures than those with less experienced. So, people should limit their physical activity in hot and humid environments.
While exercising, replace fluids regularly. Take water (2 cups or 16 ounces) before and during activity (1 cup or 5-10 ounces every 15 to 20 minutes). After an activity, replace 16 ounces of fluid for each pound of weight lost. For exercising more than one hour, fluid replacement drinks containing simple carbohydrates (glucose, fructose, or sucrose) and electrolytes cools the body temperature. If the concentration of sugar is not more than 4-8 percent, then it can replace fluids faster.
Tips to do physical exercises in hot and humid environment:
- Gradually expose yourself to physical activity.
- Don’t change your wet shirt which cools the body better.
- Rest at regular intervals.
- Wear white or light colors that can reflect the heat rather than absorbing it. A porous hat or cap can help when exercising in direct sunlight.
- Watch for signs of heat stress. If signs are present, stop immediately.
Tips to be done after exercising:
- Drink excess water to prevent dehydration.
- Immerse the body in cool water.
- If symptoms of heat stroke are present, seek medical attention and stretch cramped muscle.