2. Piokilotherms vs Homeotherms Piokilotherms: at mercy of the elements Piokilotherms: at mercy of the elements Homeotherms: can function independent of the environment Homeotherms: can function independent of the environment Ability to maintain constant temperature Ability to maintain constant temperature

3. Normal body temperature: 36.5- 37.5°C During exercise can increase to 40°C with no ill effects During exercise can increase to 40°C with no ill effects Core temp: temperature of the hypothalamus, temperature regulator of the body Core temp: temperature of the hypothalamus, temperature regulator of the body Thermal gradients: temperature differences from one point to another the lead to movement of heat Thermal gradients: temperature differences from one point to another the lead to movement of heat Temperature always equilibrates from hot to cold Temperature always equilibrates from hot to cold

4. Temperature Regulation Metabolism Metabolism Shivering Shivering Nonshivering thermogenesis Nonshivering thermogenesis Metabolic Rate Metabolic Rate Heat loss Heat loss

5. Metabolism Heat is produced naturally during normal metabolic reactions Heat is produced naturally during normal metabolic reactions Most reactions lose ~75% of energy as heat Most reactions lose ~75% of energy as heat At BMR heat loss is ~100 kcal/hr At BMR heat loss is ~100 kcal/hr BMR is porportional to ¾ power of body weight (surface rule) BMR is porportional to ¾ power of body weight (surface rule)

6. Shivering Main mechanism for increasing heat during negative heat balance Main mechanism for increasing heat during negative heat balance Involuntary muscle contraction Involuntary muscle contraction Maximum shivering can increase body’s heat production 5X Maximum shivering can increase body’s heat production 5X

7. Preshivering tone can increase heat production 50-100% Preshivering tone can increase heat production 50-100% An effective way to increase body temperature b/c no work is done by the muscles and most of the energy is expended is heat An effective way to increase body temperature b/c no work is done by the muscles and most of the energy is expended is heat Increases Q by increasing SV via increased venous return Increases Q by increasing SV via increased venous return Limits: glycogen depletion, hypoglycemia, fatigue, ex., hypoxia, drugs (alcohol and barbiturates) Limits: glycogen depletion, hypoglycemia, fatigue, ex., hypoxia, drugs (alcohol and barbiturates)

8. Nonshivering thermogenesis Increased thyroxin secretion (thyroid) and catecholamine secretion (adrenals) increase metabolic rate Increased thyroxin secretion (thyroid) and catecholamine secretion (adrenals) increase metabolic rate Thyroxin increases the rate of all cells Thyroxin increases the rate of all cells Cats., esp norepi. release FFA, increasing metabolic rate Cats., esp norepi. release FFA, increasing metabolic rate

9. Metabolic Rate (Q10 and food) Q10 is rate of a physiologic process at a particular temperature to the rate at a temperature 10°C lower Q10 is rate of a physiologic process at a particular temperature to the rate at a temperature 10°C lower Increased metabolic rate can be self- perpetuating (dangerous) Increased metabolic rate can be self- perpetuating (dangerous)

10. At high temperatures, hypothalamus loses ability to cool the body At high temperatures, hypothalamus loses ability to cool the body Rate of temperature increases faster at higher temperatures Rate of temperature increases faster at higher temperatures Metabolic rate temporarily increases following food intake, esp. proteins Metabolic rate temporarily increases following food intake, esp. proteins

11. Heat Loss Radiation Radiation Conduction Conduction Convection Convection Evaporation Evaporation

12. Radiation Loss or gain in the form of electromagnetic waves Loss or gain in the form of electromagnetic waves At rest, in a comfortable environment, radiation accounts for 60% of total heat loss At rest, in a comfortable environment, radiation accounts for 60% of total heat loss Varies with body position and clothes Varies with body position and clothes Human skin, regardless of color, absorbs ~97% of radiant energy that strikes it Human skin, regardless of color, absorbs ~97% of radiant energy that strikes it

13. Conduction Transfer of heat from a body to an object Transfer of heat from a body to an object Or, heat transfer within an organism down a thermal gradient Or, heat transfer within an organism down a thermal gradient ~3% of total heat loss at room temperature occurs this way ~3% of total heat loss at room temperature occurs this way

14. Convection Conduction of heat to air or water Conduction of heat to air or water Amounts to ~12% of all heat lost at room temperature Amounts to ~12% of all heat lost at room temperature Heat is conducted to water or air, moves so that other molecules can be heated Heat is conducted to water or air, moves so that other molecules can be heated Faster in water or air? Faster in water or air?

15. Greater in the wind (air movement) Greater in the wind (air movement) Wind chill effect Wind chill effect Can also occur in the circulatory system Can also occur in the circulatory system Heat moves with the blood from the core to the periphery Heat moves with the blood from the core to the periphery As skin temp. incr., heat loss to environment increases As skin temp. incr., heat loss to environment increases Rate is affected by blood flow and temperature gradient (core/periphery) Rate is affected by blood flow and temperature gradient (core/periphery)

16. Evaporation ~25% of heat is lost this way in a comfortable environment ~25% of heat is lost this way in a comfortable environment Quantity of heat absorbed by sweat as it evaporates: latent heat of vaporization Quantity of heat absorbed by sweat as it evaporates: latent heat of vaporization Body loses 0.58 kcal/gm H 2 O evaporates Body loses 0.58 kcal/gm H 2 O evaporates Only means of cooling at high environmental temperatures, Critical for exercise Only means of cooling at high environmental temperatures, Critical for exercise

17. If body cannot lose heat this way, body temp. increases rapidly If body cannot lose heat this way, body temp. increases rapidly Sweat is only effective if it evaporates Sweat is only effective if it evaporates High humidity: evaporation reduced or prevented High humidity: evaporation reduced or prevented Effective evaporation also hampered by little air movement Effective evaporation also hampered by little air movement

18. Women have a lower sweating capacity than men do Women have a lower sweating capacity than men do Process occurs by sweating and insensible water loss: ventilation, diffusion through skin, does not include sweat, urine, and feces Process occurs by sweating and insensible water loss: ventilation, diffusion through skin, does not include sweat, urine, and feces Sweat rates are at 0 when temperature is low Sweat rates are at 0 when temperature is low

19. Hypothalamus and temperature regulation Temperature regulatory center Temperature regulatory center Responds to heat primarily through heat-sensitive neurons in the preoptic area of anterior portion Responds to heat primarily through heat-sensitive neurons in the preoptic area of anterior portion More cold than heat receptors in the skin More cold than heat receptors in the skin Thermoregulators transmit impulses to the spinal cord, to hypothalamus, initiates response Thermoregulators transmit impulses to the spinal cord, to hypothalamus, initiates response

20. Ant. Hypothalamus stimulates the sweat glands, evaporative heat loss Ant. Hypothalamus stimulates the sweat glands, evaporative heat loss “Hunting Reflex” primarily in hands and feet “Hunting Reflex” primarily in hands and feet Hypothalamus is the body’s thermostat Hypothalamus is the body’s thermostat Set-point it tries to keep Set-point it tries to keep Sweating normally occurs at 37°C Sweating normally occurs at 37°C Set-point can change in response to dehydration, starvation, and fever Set-point can change in response to dehydration, starvation, and fever

21. Exercise in the Cold Clothing Clothing Oxygen Consumption Oxygen Consumption Ventilation Ventilation Heart Heart Muscle Strength Muscle Strength Metabolic Changes Metabolic Changes

22. Clothing Insulation value of clothing must be balanced with increased metabolic production of the exercise Insulation value of clothing must be balanced with increased metabolic production of the exercise Traps warm air next to the skin an decreases heat loss by conduction and convection Traps warm air next to the skin an decreases heat loss by conduction and convection Should be worn in layers Should be worn in layers

23. Oxygen Consumption Maximum uptake is unaffected by the cold Maximum uptake is unaffected by the cold Submax. VO 2 increases in the cold Submax. VO 2 increases in the cold Why? Why? Shivering can persist during exercise, which also can increase VO 2 Shivering can persist during exercise, which also can increase VO 2

24. Ventilation Increases in the cold, particularly if exposure is sudden Increases in the cold, particularly if exposure is sudden Abrupt exposure can lead to gasping reflex Abrupt exposure can lead to gasping reflex

25. Heart Cold exposure causes peripheral vasoconstriction, increase central BV Cold exposure causes peripheral vasoconstriction, increase central BV BP increase due to increased afterload and sometimes increased preload too BP increase due to increased afterload and sometimes increased preload too SV may increase, inc. EDV SV may increase, inc. EDV Changes in cardiac performance more common in men Changes in cardiac performance more common in men Incidence of arrhythmias increase in cold Incidence of arrhythmias increase in cold

26. Muscle Strength Strength decreases with lower muscle temp. Strength decreases with lower muscle temp. Also lower enzyme activity Also lower enzyme activity Increased MU recruitment may be necessary to compensate Increased MU recruitment may be necessary to compensate Other factors: increased muscle viscosity, decreased ATP metabolism and contractility Other factors: increased muscle viscosity, decreased ATP metabolism and contractility

27. Metabolic Changes Increase use of CHO as substrate Increase use of CHO as substrate Light ex: glycogen depletes faster Light ex: glycogen depletes faster Max ex: depletion is independent of temp. Max ex: depletion is independent of temp. Prolonged exposure to cold: hypoglycemia, suppresses shivering, core temp drops, lactate higher Prolonged exposure to cold: hypoglycemia, suppresses shivering, core temp drops, lactate higher Fat metabolism suppressed, even though cat. response is higher Fat metabolism suppressed, even though cat. response is higher

28. Acclimatization and Habituation to Cold Acclimatize: physiologic compensation to environmental stress over time Acclimatize: physiologic compensation to environmental stress over time Habituation: lessening of the sensation associated with an environment Habituation: lessening of the sensation associated with an environment Shivering threshold Shivering threshold First test of acclimatization First test of acclimatization Cold-acclimatized people maintain heat production with less shivering, more nonshivering thermogenesis Cold-acclimatized people maintain heat production with less shivering, more nonshivering thermogenesis

29. Hand and Feet temperature Hand and Feet temperature Second test for acclimatization Second test for acclimatization Acclimatized: maintain almost normal temperature Acclimatized: maintain almost normal temperature Habituation also plays a role Habituation also plays a role Ability to sleep in the cold Ability to sleep in the cold Third and final test Third and final test Seems to depend on extent of nonshivering thermogenesis induced by increased secretion of norepi Seems to depend on extent of nonshivering thermogenesis induced by increased secretion of norepi

30. Hypothermia Depresses the CNS, lose ability to shiver, sleepiness, coma, death Depresses the CNS, lose ability to shiver, sleepiness, coma, death Lower temp: lower cellular met. rate, further lowering temp. Lower temp: lower cellular met. rate, further lowering temp. Profound effects on the CV system Profound effects on the CV system Central BV decreases; plasma sequestration, inadequate fluid intake, cold diuresis Central BV decreases; plasma sequestration, inadequate fluid intake, cold diuresis

31. Risk factors Risk factors cold exposure cold exposure Lack of protective clothing Lack of protective clothing Leanness Leanness Inadequate fluid intake Inadequate fluid intake High wind chill High wind chill Use of alcohol &/or drugs Use of alcohol &/or drugs Use of snow to relieve thirst Use of snow to relieve thirst Glycogen depletion Glycogen depletion

32. Frostbite Caused by ice crystal formation within the tissue Caused by ice crystal formation within the tissue Occurs in exposed skin Occurs in exposed skin Can lead to tissue death Can lead to tissue death

33. Exercise in the Heat

34. Cardiovascular Effects

35. Plasma volume decreases during exercise in the heat becomes acute at intensity increases becomes acute at intensity increases decrease of plasma volume is made worse by loss of body fluids through sweating decrease of plasma volume is made worse by loss of body fluids through sweating may not be enough blood to adequately perfuse all areas during exercise in the heat may not be enough blood to adequately perfuse all areas during exercise in the heat

36. central blood volume may decrease and cause a decrease in cardiac filling pressure central blood volume may decrease and cause a decrease in cardiac filling pressure results in increased HR in attempt to compensate for lower SV results in increased HR in attempt to compensate for lower SV submax. HR increases also submax. HR increases also @ max levels, skin vessels vasoconstrict to help maintain blood pressure and Q @ max levels, skin vessels vasoconstrict to help maintain blood pressure and Q

37. negative response on heat transfer negative response on heat transfer circulatory regulation takes precedence over temperature regulation in this case circulatory regulation takes precedence over temperature regulation in this case VO2 max is not impaired in the heat unless the person was experiencing thermal imbalance before beginning the exercise VO2 max is not impaired in the heat unless the person was experiencing thermal imbalance before beginning the exercise

38. Sweating Response primary means of heat dissipation during exercise (evaporation) primary means of heat dissipation during exercise (evaporation) in heat, sweating is very important b/c body tends to gain rather than lose heat by radiation, conduction, and convection in heat, sweating is very important b/c body tends to gain rather than lose heat by radiation, conduction, and convection during exercise, sweating is related more to intensity than environmental temperature during exercise, sweating is related more to intensity than environmental temperature

39. Acclimatization to heat first two weeks of heat exposure results in lower heart rate, core temperature, RPE, and skin temperature at rest and during exercise first two weeks of heat exposure results in lower heart rate, core temperature, RPE, and skin temperature at rest and during exercise primary physiological adjustments are increased peripheral heat conductance, plasma volume, and sweating, decreased core temperature at onset of sweating, and improved distribution of sweat over the skin primary physiological adjustments are increased peripheral heat conductance, plasma volume, and sweating, decreased core temperature at onset of sweating, and improved distribution of sweat over the skin

40. CV Adaptations acclimatization induces a 3-27% increase in plasma volume, if acclimatization is done with exercise training acclimatization induces a 3-27% increase in plasma volume, if acclimatization is done with exercise training increased plasma volume helps to maintain SV, central blood volume, and sweating capacity increased plasma volume helps to maintain SV, central blood volume, and sweating capacity also increases in vasopressin, renin, and aldosterone in early days also increases in vasopressin, renin, and aldosterone in early days

41. blood flow to the skin decreases blood flow to the skin decreases decreased skin blood flow helps to maintain central blood volume, which is vital for maintaining BP, SV, and muscle blood flow during exercise decreased skin blood flow helps to maintain central blood volume, which is vital for maintaining BP, SV, and muscle blood flow during exercise core temperature is lower during exercise core temperature is lower during exercise decrease in skin blood flow is accompanied by a large increase in sweating and evaporative cooling capacity decrease in skin blood flow is accompanied by a large increase in sweating and evaporative cooling capacity

42. Sweating Response acclimatization increases this response almost 3X, from ~1.5 l/hr to 4 l/hr acclimatization increases this response almost 3X, from ~1.5 l/hr to 4 l/hr accompanied by a more even distribution of sweating accompanied by a more even distribution of sweating sweat losses of sodium chloride decrease b/c of increased secretion of aldosterone sweat losses of sodium chloride decrease b/c of increased secretion of aldosterone

43. Thermal Distress includes dehydration, heat cramps, heat exhaustion, heat syncope, and heat stroke includes dehydration, heat cramps, heat exhaustion, heat syncope, and heat stroke hyperthermia is caused by an imbalance between heat gain and heat loss hyperthermia is caused by an imbalance between heat gain and heat loss

44. Dehydration loss of fluid from the body loss of fluid from the body can decrease sweat rate, plasma volume, Q, VO2 max, work capacity, muscle strength, and liver glycogen can decrease sweat rate, plasma volume, Q, VO2 max, work capacity, muscle strength, and liver glycogen at fluid deficit of 5% of BW, symptoms include discomfort, and alternating states of lethargy and nervousness at fluid deficit of 5% of BW, symptoms include discomfort, and alternating states of lethargy and nervousness level >7% is extremely dangerous level >7% is extremely dangerous

45. at levels >10%, ability to walk is impaired, and is accompanied by discoordination and spasticity at levels >10%, ability to walk is impaired, and is accompanied by discoordination and spasticity as 15% is neared, the person experiences delirium, shriveled skin, along with decreased urine volume, loss of ability to swallow food, and difficulty swallowing water as 15% is neared, the person experiences delirium, shriveled skin, along with decreased urine volume, loss of ability to swallow food, and difficulty swallowing water >20% the skin bleeds and cracks >20% the skin bleeds and cracks

46. thirst does not keep up with fluid requirements thirst does not keep up with fluid requirements physical fitness helps prevent this physical fitness helps prevent this during prolonged exercise, can develop hyponatremia, caused by excessive sodium loss in the sweat without adequate replacement during prolonged exercise, can develop hyponatremia, caused by excessive sodium loss in the sweat without adequate replacement

47. Heat cramps characterized by involuntary cramping and spasm in muscle groups used during exercise characterized by involuntary cramping and spasm in muscle groups used during exercise it occurs in people who have exercised and sweated heavily it occurs in people who have exercised and sweated heavily often the individual is conditioned and acclimatized often the individual is conditioned and acclimatized fluid and electrolyte replacement, rest, some say magnesium helps fluid and electrolyte replacement, rest, some say magnesium helps

48. Heat exhaustion rapid, weak pulse, hypotension, faintness, profuse sweating and psychological disorientation rapid, weak pulse, hypotension, faintness, profuse sweating and psychological disorientation results from acute plasma volume loss and inability of the circulation to compensate for the concurrent vasodilation in the skin and the active working muscles results from acute plasma volume loss and inability of the circulation to compensate for the concurrent vasodilation in the skin and the active working muscles

49. Treatment have person lie down in cool area have person lie down in cool area administer fluids administer fluids rest and drink plenty of fluids for next 24 hr. rest and drink plenty of fluids for next 24 hr. not allowed to participate for rest of the day not allowed to participate for rest of the day

50. Heat syncope related to heat exhaustion, but can occur without major sweat loss related to heat exhaustion, but can occur without major sweat loss typically, it occurs after exercise when the individual stops moving and blood pools typically, it occurs after exercise when the individual stops moving and blood pools can occur secondary to heat exhaustion or independently can occur secondary to heat exhaustion or independently

51. Heat stroke failure of hypothalamic temperature regulatory center; represents a major medical emergency failure of hypothalamic temperature regulatory center; represents a major medical emergency principally caused by failure of the temperature regulatory center in hypothalamus, which causes failure of the body’s heat loss mechanisms principally caused by failure of the temperature regulatory center in hypothalamus, which causes failure of the body’s heat loss mechanisms

52. characterized by a high core temperature, hot, dry skin, and extreme CNS dysfunction characterized by a high core temperature, hot, dry skin, and extreme CNS dysfunction associated with increases in plasma norepinehprine, epi, and endotoxin levels that have been associated with vascular collapse associated with increases in plasma norepinehprine, epi, and endotoxin levels that have been associated with vascular collapse risk is greatest in high temperatures, humidity, hottest time of the day, and on days with little wind risk is greatest in high temperatures, humidity, hottest time of the day, and on days with little wind

53. Treatment cool person with tepid water cool person with tepid water ice packs on the groin, neck, and axilla ice packs on the groin, neck, and axilla send to hospital ASAP send to hospital ASAP

54. Prevention ensure athletes are well-conditioned ensure athletes are well-conditioned avoid overheating avoid overheating be aware of early symptoms of heat stress: thirst, fatigue, lethargy, and visual disturbances be aware of early symptoms of heat stress: thirst, fatigue, lethargy, and visual disturbances athletes should not train harder than normal intensity athletes should not train harder than normal intensity should not compete if have an illness accompanied by a fever should not compete if have an illness accompanied by a fever

55. schedule practice during the cooler times of the day schedule practice during the cooler times of the day modify or cancel sessions when the wet bulb temperature is 25.5°C or greater modify or cancel sessions when the wet bulb temperature is 25.5°C or greater plan regular fluid breaks plan regular fluid breaks supply a drink that is cold and contains some CHO and electrolytes supply a drink that is cold and contains some CHO and electrolytes

56. hyperhydrate before activity hyperhydrate before activity fluid replacement should be encouraged during the early stages of practice and competition fluid replacement should be encouraged during the early stages of practice and competition athletes should be weighed every day before and after practice. If a 2-3% decrease in weight, should consume more fluid, if 4-6%, should decrease activity levels, 7% loss, consult a physician athletes should be weighed every day before and after practice. If a 2-3% decrease in weight, should consume more fluid, if 4-6%, should decrease activity levels, 7% loss, consult a physician

57. Rhabdomyolysis Myoglobin excretion is increased Myoglobin excretion is increased Myoglobin is cleared by the kidneys Myoglobin is cleared by the kidneys Kidneys shut down, especially with heat Kidneys shut down, especially with heat Can lead to death Can lead to death Occurs with excessive exercise Occurs with excessive exercise Rare Rare May be a predisposition, latent metabolic disorder May be a predisposition, latent metabolic disorder Diuretics contribute to this Diuretics contribute to this CHO as well, but a rare possibility CHO as well, but a rare possibility