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Thermoregulation. Chapter 10. Mechanisms of Body Temperature Regulation . Transfer of Body Heat Conduction Convection Radiation Evaporation Humidity and Heat Loss. Mechanisms of Body Temperature Regulation. Effect of air temperature on effectiveness of avenues of heat loss.
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Thermoregulation Chapter 10
Mechanisms of Body Temperature Regulation • Transfer of Body Heat • Conduction • Convection • Radiation • Evaporation • Humidity and Heat Loss
Effect of air temperature on effectiveness of avenues of heat loss
Mechanisms of Body Temperature Regulation • Efficiency of Energy Systems and Temperature • Hypothalamus • Body Temperature and Effectors • Sweat glands • Smooth muscle around arterioles • Skeletal muscle • Endocrine glands
Physiological Responses to Exercise in the Heat • CV Responses • Energy Production • Glycogen dependence and lactate • Driven by epinephrine • Body Fluid Balance – Sweating • Heavy and light sweating – electrolytes • Blood volume changes – aldosterone and ADH secretion
Exercise in the Heat • Heat Stress • Air temperature, humidity, air velocity, & amount of thermal radiation all influence heat stress • Wet bulb globe temperature (WBGT) – designed to account for all avenues of heat loss and gain. • Difference between WB and dry bulb is an indicator of environments ability to cool by evaporation • Black globe temperature is an indicator of environments capacity for transmitting radiated heat. • Overall challenge to body temperature is expressed as WBGT • WBGT = 0.1 TDB + 0.7 TWB + 0.2 TG
Exercise in the Heat • Heat Related Disorders • Heat Cramps • Ss - severe cramping of primary muscles due to mineral losses and dehydration • Tx – move to cooler location and administer fluids or saline solution • Heat Exhaustion • Ss – extreme fatigue, dizziness, dyspnea, nausea, cold or clammy or hot and dry skin, weak, rapid pulse. • CV unable to meet body’s needs • Tx – move to cooler environment with elevated feet, salt water administered, IV saline if unconcious. If untreated can result in heat stroke
Exercise in the Heat • Heat Stroke • Ss – core temperature >40⁰C (104 ⁰ F, cessation of sweating, hot and dry skin, rapid pulse and respiration, hypertension, confusion or unconciousness • Untreated can progress to coma and death • Tx – rapid cooling in a cold bath or wrapping in wet sheets and fanning the victim • Cause is failure of thermoregulatory mechanisms
Exercise in the Heat • Preventing Hyperthermia • When possible decrease effort to decrease heat production • Recognize Ss of hyperthermia • When WBGT exceeds 28 ⁰C (82.4 ⁰ F) do not practice or compete outdoors • Frequent fluid breaks • Appropriate clothing – skin exposure
Heat Acclimatization • Adjustments of the body to repeated, prolonged exercise bouts in the heat • Result is an increased ability to dissipate heat and reduce risk of heat illness • Sweat rate increases • Amount of sweat produced in exposed areas increases • Sweating starts earlier – creates heat gradient • Less mineral content in sweat
Heat Acclimatization • Body temperature and heart rate increase to a lesser degree during exercise at any heat load • Decrease rate of glycogen utilization after acclimitization
Heat Acclimatization • Achieving heat acclimatization depends on exposure to a hot environment plus • The environmental conditions during each session • Duration of heat exposure • Intensity of exercise • 5-10 days of training in the heat will result in acclimatization. • Training intensity should be reduced in first few days to prevent heat illness
Exercise in the Cold • Cold Stress – any environmental condition that causes a loss of body heat that threatens homeostasis • A decrease in skin or blood temperature stimulates mechanisms designed to produce heat and conserve heat
Exercise in the Cold • Mechanisms: • Shivering • Nonshiveringthermogenesis • Peripheral vasoconstriction • Factors to consider in heat loss • Temperature gradient • Surface area • Windchill
Exercise in the Cold • Physiological Responses to Exercise in the Cold • Muscle function • Metabolic responses • Health Risks • Hypothermia • Cardiorespiratory effects
Acclimatization to the Cold • Increased subcutaneous fat • Greater cold tolerance • Increased blood flow and warming of exposed areas