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.
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.
Cancel training or competition if the environmental heat stress to high, wearing proper clothing, being alert to signs of hyperthermia, ensuring adequate fluid intake.
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.
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.
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.
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.
Hypothermia - dry clothing, warm beverages, slow rewarming, hospital treatment. Frostbite - left untreated until can be thawed, best in a hospital.
Chronic daily exposure to cold water increase subcutaneous fat. Repeated exposure to cold - alter peripheral blood flow and skin temperature - greater cold tolerance.
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).
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.
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
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.
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.