Exercise Physiology Chapter 25: Exercise and Thermal Stress

9. The small intestine can absorb about

1000 mL of water each hour. A small amount of electrolytes in the rehydration beverage facilitates fluid replacement more than drinking plain water.

3. Subcutaneous fat provides excellent insulation against

cold stress. It greatly enhances the effectiveness of vasomotor adjustments, so individuals with excess body fat retain a large percentage of metabolic heat.

5. Wearing appropriate clothing enables humans to tolerate some of the

coldest climates on Earth.

6. Ambient temperature and wind influence the

coldness of an environment. The wind-chill index determines the wind's cooling effect on exposed tissue.

7. Pronounced peripheral vasoconstriction during severe cold exposure causes

dangerously low skin and extremity temperatures when compounded by marked increases in convective and conductive heat loss.

11. Repeated heat stress initiates thermoregulatory adjustments that improve physical capacity and reduce

discomfort on heat exposure.

12. Ten days of heat exposure promotes

full acclimatization.

2. Heat production from shivering and physical activity offsets

heat flux to a cold environment. Shivering increases the metabolic rate by 3 to 6 METs.

14. Women and men show equivalent thermoregulation during physical activity when controlled for

levels of fitness and acclimatization. Women produce less sweat than men when exercising at the same core temperature.

1. Core temperature normally increases during physical activity; the relative stress of activity determines the

magnitude of the increase.

15. Heat cramps, heat exhaustion, and heat stroke constitute the

major heat illnesses. Heat stroke, a medical emergency, is the most serious and complex of these maladies.

2. A well-regulated temperature increase creates a more favorable environment for

physiologic and metabolic functions.

8. Considerable water loss occurs from the respiratory passages during physical activity on a cold day, but inspired air temperature generally does not

pose a danger to respiratory tract tissues.

4. Individuals exhibit much less physiologic adaptation to chronic cold stress than to

prolonged heat exposure.

3. Excessive sweating compromises fluid reserves to create a

relative state of dehydration.

10. The diet generally replaces minerals lost through

sweating. With prolonged exercise in the heat, adding a small amount of salt to the replacement fluid (1 tsp ∙ L−1) facilitates sodium and fluid replenishment.

5. Physical activity in a hot, humid environment poses a considerable thermoregulatory challenge because

the large sweat loss in high humidity contributes little to evaporative cooling.

1. Water conducts heat about 25 times faster than air; immersion in water of only 28 to 30°C (82 to 86°F) provides considerable

thermal stress that initiates rapid thermoregulatory adjustments.

16. Oral temperature after physical activity inaccurately measures core temperature because of e

vaporative cooling of the mouth and airways with high levels of pulmonary ventilation during activity and recovery.

4. Sweating without fluid replacement decreases plasma volume, which leads to

circulatory dysfunction and a precipitous rise in core temperature.

9. The Ama, the women divers of Korea and southern Japan, display

cold adaptation from a blunted thermogenic response to prolonged diving that allows them to effectively tolerate extreme cold.

13. Aging affects thermoregulatory functions but does not

appreciably alter temperature regulation during exercise or acclimatization to moderate heat stress.

6. Fluid loss of more than 4% of body weight impedes heat dissipation, compromises

cardiovascular function, and diminishes exercise capacity.

8. The ideal replacement schedule during physical activity matches fluid intake to fluid loss, a process effectively monitored by

changes in body weight.

7. Adequate fluid replacement maintains plasma volume so

circulation and sweating progress optimally.