Chapter Environment: Acclimate, Then Perform C H A P T E R

Objectives This chapter will help you do the following: Anticipate the effects of the environment on performance Take appropriate steps to minimize environmental effects Understand how fitness enhances your ability to acclimatize and perform in difficult environments

Regulating Body Temperature Regulating center is located in the hypothalamus. The hypothalamus serves as a thermostat to maintain body temperature at or near 37 degrees Celsius (98.6 degrees Fahrenheit). Heat and cold receptors located in the skin sense changes in environmental temperature conditions. Regulators such as muscles increase body heat with shivering or exercise. Vasomotor (nervous system) controls constrict or dilate arterioles to conserve or lose body heat.

Individual Differences Influencing Regulating Body Temperature Body fat This is the layer of insulation beneath the surface of the skin. Sweat glands Evaporative heat loss is the most important protection against heat stress; a good supply of active sweat glands is important. (continued)

Individual Differences Influencing Regulating Body Temperature (continued) Physical fitness Enhances the ability to regulate body temperature during work in the heat. Sex Men produce more sweat than women do for a given increase in body temperature, and perhaps too much. Women are efficient sweaters. (continued)

Individual Differences Influencing Regulating Body Temperature (continued) Other factors can influence your response to heat. Illness Medications Drugs Alcohol

Exercising in the Heat The temperature-regulating center increases the usual set point of the body, allowing body temperature to increase. The higher set point also serves to reduce the problem of heat dissipation. Under moderate environmental conditions, the body does not employ methods of heat dissipation until the elevated set point has been reached.

Fluid Replacement Dehydration in excess of 5 percent of body weight leads to a marked decline in strength, endurance, and work capacity. The thirst mechanism always underestimates fluid loss during work in the heat and after work ends. Assess your level of dehydration by observing the color of your urine. (continued)

Fluid Replacement (continued) Hyponatremia Excess intake of water during prolonged vigorous effort can lead to a dangerously low concentration of sodium. Electrolytes For each liter of sweat lost, approximately 1.5 grams of salt are lost as well. Carbohydrates Avoid very high glucose levels (over 8 percent) in fluid- replacement solutions while running. (continued)

Fluid Replacement (continued) To maintain proper hydration, you should drink before, during, and after vigorous activity. Before: Drink 2 to 3 cups (500 to 750 milliliters) before the event. During: Drink a cup (250 milliliters) or more of fluid every 15 to 20 minutes, or 1 quart (1 liter) per hour. After: Replace fluid and carbohydrate after the event.

Figure 15.1 Heat Stress Metabolic heat cannot be dissipated, and the body temperature rises.

Heat Acclimatization Increase in circulatory and cooling efficiency is called heat acclimatization, and most of the process occurs after 5 to 10 days of work in a hot environment (increases in sweat rate may take longer). The best way to acclimatize is to work in the actual conditions (temperature and humidity) that you will have to endure.

Rhabdomyolysis Damaged skeletal muscle tissue releases the breakdown products into the bloodstream. Risk factors include a sedentary lifestyle, high ambient temperatures, and intense or extreme exercise. Some are genetically more susceptible to rhabdomyolysis.

Exercising in the Cold Windchill The effect of wind speed on heat loss Frostbite Damage to the skin resulting from exposure to extreme cold or windchill (continued)

Exercising in the Cold (continued) Hypothermia –Occurs when heat is lost more quickly than body can produce it. –If someone exhibits the symptoms of hypothermia, transport the victim to a medical facility as quickly as possible. Cold weather clothing –Clo unit (refer to figure 15.3) –Perspiration is a major problem during exercise in the cold.

Cold Acclimatization This is a metabolic adjustment wherein metabolism increases as much as 35 percent. Repeated exposure to cold seems to lead to physiological and psychological adjustments that allow one to tolerate and enjoy physical activity in cold environments. Hydration is necessary during exercise in the cold.

Altitude Acclimatization Profound changes occur soon after one ascends to a higher elevation. –Pulmonary ventilation increases. –Oxygen transport gradually improves through increases in red blood cells, hemoglobin, and blood volume. –Higher elevations may cause an increase in lung and muscle capillaries and myoglobin, the molecule that serves to store oxygen in muscles. A good adjustment to higher elevation occurs in about 3 weeks, or about 1 week for each 1,000 feet (300 meters) above 5,000 feet (1,500 meters).

Altitude Training For years, coaches and athletes have sought the ultimate training stimulus at a moderate altitude of 5,000 to 10,000 feet (1,500 to 3,000 meters). Unfortunately, the effort may not be worth it for all athletes. Training at altitude is, in reality, a product of natural selection combined with long-term residence at a higher elevation, not just a few weeks of altitude training.

Avoiding the Effects of Air Pollution We are beginning to recognize the many sources of air pollution as threats to the quality of life and to life itself. Avoid exercise in obviously dangerous areas (along expressways, near industrial pollution) and when air pollution warnings are in effect.

Summary Chapter 15 outlined the problems encountered in various environments and provided practical advice on how to minimize the problems and maximize performance and enjoyment.