The document discusses environmental influences on human performance during exercise in various conditions. It covers mechanisms of body temperature regulation and how factors like humidity, air temperature, and hydration impact heat exchange. It also discusses physiological responses to exercise in heat, cold, high altitude/hypobaric, underwater/hyperbaric, and microgravity environments, as well as health risks associated with exercising in extreme environments like heat stroke, hypothermia, altitude sickness, and decompression sickness.

1. ENVIRONMENTAL INFLUENCES ON PERFORMANCE Thermal Regulation And Exercise Mechanisms of Body Temperature Regulation The heat from deep of body (core) is moved by blood to the skin (the shell). From there transferred to the environment by: conduction, convection, radiation, evaporation

3. Conduction, convection - heat loss 10 - 20 percent Radiation - 60 percent during rest (infrared, electromagnetic waves) Evaporation - 80 percent of heat loss during exercise Heat production at rest - 1,5 kcal of heat/min. at exercise - 15 kcal/min. Humidity high - limits sweat evaporation and heat loss low - ideal for sweat evaporation and heat loss.

5. Control of Heat Exchange Hypothalamus - Body´s Thermostat

7. Thermoregulatory center - hypothalamus Two sets of thermoreceptors: central -hypoth. peripheral - in skin (temperature around the body) impulses to hypoth. and cerebral cortex - consciously perceive temperature - voluntary control exposure to heat or cold.

8. Effectors Altering Body Temperature Sweat glands, smooth muscles around arterioles, skeletal muscles, endocrine glands (thyroxin, epinephrine)

9. Physiologic Responses to Exercise in the Heat Exercise in Hot Enviroment Competition between active muscles and skin for limited blood supply muscles - blood and oxygen for sustain activity, skin - blood to facilitate heat loss to keep the body cool.

10. Cardiovascular Response Adjustement -  blood volume returning to the heart -  end. diastolic volume - ↓ SV - compensation - gradual upward drift in HR  cardiovascular drift . Energy Production Exercise in hot enviroment -  O 2 uptake, use of more glycogen, produce more lactate - earlier fatigue and exhaustion

11. Body Fluid Balance - Sweating Sweat - filtration of plasma. Reabsorption of Na and Cl´ in passing through the duct. Increased sweat rates - quick movement, less time for reabsorption - loss of natrium and chloride - with training - aldosterone stimulates for more reabsorption of Na´, Cl´ . Sweat production in hot - 1l/HR/m2 - 2 - 4 percent of body weight   blood volume - dehydration. Triggering aldosterone, ADH  Na´ excretion in kidneys ADH - water reabsorption in kidneys  fluid retention.

13. HEALTH RISKS DURING EXERCISE IN THE HEAT Heat Stress - reflected not only by air temperature, further variables take into account: humidity, air velocity, amount of radiation. Heat-related Disorders 1) Heat Cramps Involving muscles heavily used during exercise, brought on by mineral losses and dehydration accompanying high rates of sweating. 2) Heat Exhaustion Symptoms: fatigue, dyspnea, dizzines, vomiting, fainting, clammy, or hot dry skin, hypotension, weak, rapid pulse - cause:CV system´s inability to adequately meet the body´s needs. Treatment - rest in cooler enviroments, feet elevated, salt water.

14. 3) Heat Stroke - Life - Threatening Disorder CHARACTERISTICS:  internal body temperature  40 o C, cessation of sweating, hot, dry skin, rapid pulse and respiration, hypertension, confusion, unconsciousness. CAUSE: failure of thermoregulatory mechanism Treatment - cooling body in a bath of cold water or ice, or wrapping the body in wet sheets and fanning.

15. Prevention of Hyperthermia Cancel training or competition if the environmental heat stress to high, wearing proper clothing, being alert to signs of hyperthermia, ensuring adequate fluid intake. Heat Acclimatization Exercise in the heat for up to an hour each day for 5 to 10 days. CV changes occur in the first 3 - 5 days, sweating mechanisms take longer, up to 10 days. Heat acclimatization -  the rate of muscles glycogen use, delaing fatigue.

16. EXERCISE IN THE COLD Cold Stress - environmental condition causing loss of body heat threatening homeostasis, two major cold stressors: air and water. Primary means CONSERVING BODY HEAT activated by hypothalamus: SHIVERING -  4 - 5 fold increase resting heat production NONSHIVERING THERMOGENESIS -  metabolism by sympathetic nervous s. -  internal heat production PERIPHERAL VASOCONSTRICTION - sympathetic stimulation smooth muscles in arterioles -  heat loss metabolism of skin cells -  less O 2 requirement

17. FACTORS AFFECTION BODY HEAT LOSS a) Body Size And Composition - subcutaneous fat - more fat mass - conservation heat more efficiently - ratio of body surface area to body mass.  ratio - lower susceptibility to hypothermia - gender - defferences minimal b) Windchill Wind - increase the rate of heat loss via convection and conduction

18. Heat Loss in Cold Water Water - thermal conductivity 26 times greater than air. The body loses heat 4 x faster in water than in air of the same temperature. Internal body´s temperature remain constant at temperature down to 32 o C. Exposure to water at 15 o C - decrease of rectal t. at 2.1 o C/hour, at 4 o C - decrease at 3.2 o C/Hr. Heat loss further increased - water moving. Survival in cold water brief - consciousness lose in minutes. Long - distance swimmers - subcutaneous fat important role - obese subjects swim for 6 h 50 min. in water 11.8 o C with no change in rectal temp. Swimmers with low body fat - 30 min - discomfort, rectal t. drop to 33.7 o C. FOR COMPETITION, water temp. between 23.9 o C - 27.8 o C seem appropriate.

19. Physiological Responses to exercise in cold When muscle is cooled, it is weakened and fatigue occurs more rapidly. Prolonged e. in cold, as energy supplies diminish and e. intensity declines, susceptibility to hypothermia increaes. E. in cold - vasoconstriction   circulation to subcutaneous fat - decrease of FFA for fuel.

20. HEALTH RISKS DURING EXERCISE IN COLD Hypothermia Decrease of body t. down bellow 34.5 o C, hypothalamus lose ability to regulate t. Completely lost at 29 o C - drowsiness and coma. Heart´s SA-node - drop of HR -  CO. Breathing cold air does not freeze the respiratory passages of the lung. Respiratory rate  , MV  . Frost Bite - vasoconstriction to the skin - reduced blood flow, skin cooled. Lack of O 2 and nutrients - skin tissue death.

21. Treatment Hypothermia - dry clothing, warm beverages, slow rewarming, hospital treatment. Frostbite - left untreated until can be thawed, best in a hospital. Cold Acclimatization Chronic daily exposure to cold water increase subcutaneous fat. Repeated exposure to cold - alter peripheral blood flow and skin temperature - greater cold tolerance.

22. EXERCISE IN HYPOBARIC, HYPERBARIC AND MICROGRAVITY ENVIRONMENT A Hypobaric environment Altitude presents a hypobaric environment. The ATMOSPHERIC PRESSURE is reduced, altitudes more than 1,500 m notable impact on human body. Reduced PO2 - decreased performance at altitude (  pressure gradient - hinders oxygen transport to tissues).

24. Air Temperature Drops as altitude increases, cold air - hold little water - dry air -  susceptibility to cold related disorders and dehydration. Solar Radiation - more intense (thinner atmosphere, drier air)

25. Physiological response to altitude  Pulmonary ventilation both at rest, exercise respiratory alkalosis (  CO 2 elimination, kidney excrete more bicarbonates - more acids in blood - compensation for alkalosis) hemoglobin saturation drops from 98 percent to 92 percent at height 2,439 m. PO 2 gradient arterial blood - tissue drops from 74 min Hj (94 - 20  74) to 40 min (60 - 20  40) at 2,439 m height. V O2 max decreases as altitude increases.

27. Plasma Volume decrease -  red blood cells concentration - more O2 transport COINCREASE by increase of HR. During maximal work - SV, HR decrease – CO DECREASE -  O 2 delivery and uptake. Oxidative capacity decreased, anaerobic energy production increase -  blood lactate level. Hypoxic vasoconstriction in pulmonary arteries  PULMONARY HYPERTENSION ENDURANCE ACTIVITY - most limited - oxidative energy production decreased. Anaerobic SPRINT ACTIVITIES  1 MIN - not limited. Thinner air - less resistance to movement (long jump record 1968 at Olympic games in Mexico city)

28. Altitude Training Hypoxic conditions -  release of erythropoetin - INCREASED RED BLOOD CELL PRODUCTION - increase blood oxygen - carrying capacity. Advantage during first few days after returning to sea level. Athletes who must perform at altitude - train at altitude of 1,500 - 3,000 m FOR AT LEAST 2 WEEKS prior to performing (adaptations to hypoxic and other environmental conditions at altitude).

29. CLINICAL PROBLEMS OF ACUTE EXPOSURE TO ALTITUDE Altitude (Mountain) Sickness Symptoms: headache , nausea, vomiting, dyspnea, insomnia Appear - 6 - 96 HR after arrival Cause - probably accumulation of CO2 in tissues Prevention - gradual ascent, no more than 300 m per day above 3,000 m Treatment - acetazol amide, dexamethazone, retreat to lower altitude

30. High Altitude Pulmonary Edema (HAPE) Symptoms: dyspnea Treatment: Retreat, oxygen High Altitude Cerebral Edema (HACE) Mental confusion, coma, death.

31. B) HYPERBARIC CONDITIONS - EXERCISING UNDERWATER Submersion in Water Exposal to hyperbaric conditions -volume decreases when pressure increases.

33. More molecules of gas are forced into solution, with rapid ascent, they come out of solution and can form bubbles - emboli develop, block major vessels, extensive tissue damage. Resting HEART RATE DECREASES by 5 - 8 beats per minute (facilitation blood return to the heart) diving in cold water - greater bradycardia, higher incidence of arrhythmias

34. BRETH-HOLD DIVING. Hyper ventilation used (  PaCO 2 ), dangerous (  PaO 2 - lose conscious ness under water). Volume of air can be reduced to RV, but no smaller. TLV/RV - limit the possible diving depth large TLV/RV - deeper diving SCUBA DIVING - inhaled gas pressurized, equal to that of water. Deeper dives  greater air flows, less time to exhaustion of the tank exhaustion.

35. Health Risks of Hyperbaric Conditions 1) Oxygen Poisoning Visual distortion, rapid, shallow breathing - convulsion. PO2  318 mm Hg - constriction of cerebral vessels. 2) Decompression Sickness Nitrogen bubbles in circulation and tissues - attempt to rapid ascent. Symptoms – pain in elbows, shoulders, knees. Treatment - placing in RECOMPRESSION CHAMBER

36. 3) Nitrogen Narcosis Symptoms - impaired judgement, similar to alcohol intoxication (for every 15 m increase in depth  1 Martini on an empty stomach). 4) Spontaneous Pneumothorax Expansion of air in lungs during ascent, over distension - rupture of aveoli. 5) Ruptured Eardrum Inability to equalize the pressure in the middle ear - force against eardrum - pain, rupture

37. C) MICROGRAVITY ENVIRONMENTS, EXERCISE IN SPACE Physiological changes during extended periods exposure to microgravity similar to those with detraining in athletes and in aging population. Weight bearing bones, antigravitational muscles are unloaded - reduced ability to function - similar effects in CV system. Strength and cross-sectional area of SA AND FA FIBERS DECREASE. BONE MINERAL DENSITY DECREASES approximately 4% from the weight bearing bones.

38. Microgravity results in body´s dumping a large percentage of plasma volume - ORTHOSTATIC HYPOTENSION ON RETURN to earth´s atmosphere. Exercise - most effective counter - measure during space flight for successful adaptation on return to earth.