Effect of temperature and altitude on exercise.pptx

Effect of temp on body

1. Effect of temperature and altitude on exercise Prepared by: Anjali dhakan Guided by: dr. sheetal patel

2. introduction Humans are homeothermic which means the internal body temperature is physiologically regulated to keep it nearly constant even when environmental temperature changes. Normal baseline temperature ranges from 36.1 to 37.8 degree Celsius. Our body is able to adapt to such environmental stresses with continued exposure over time a process known as acclimation or acclimatization. The temperature limits for living cells range from about 0 degree Celsius to 45 degree Celsius. Internal body temperatures above 40 degree Celsius can adversely effect the nervous system

3. The preoptic-anterior hypothalamus: the body’s thermostat Sensory receptors called thermoreceptors detect changes in temperature and relay this information to the bodys thermostat in the brain called as pre-optic anterior hypothalamus (POAH). Hypothalamus has a predetermined temperature set point that it tries to maintain ; that is the normal body temperature. The smallest deviation from this set point signals this center to readjust the body temperature. Thermoreceptors are located throughout the body but specially in skin and central nervous system. The central receptors are responsive to blood temperature changes as small as 0.001 degree Celsius

4. Thermoregulatory effectors Skin arterioles Eccrine sweat glands Skeletal muscle Endocrine glands

5. Physiological response to exercise in heat Exercise increases the demands on cardiovascular system. During exercise in hot conditions the circulatory system has to continuously transport blood to working muscle and skin so that the heat generated by the muscles can be transferred to the environment. Cardiac output increases further above that associated with a similar exercise intensity at a cooler condition by increasing heart rate and contractility. Secondly blood flow is shunted away from non essential areas like gut liver and kidneys and to the skin.

6. Physiological response to exercise IN heat The aerobic exercise increases both metabolic heat production and the demand for blood flow and oxygen delivery to the working muscles. This excess flow can only be dissipated if blood flow increases to the skin. In response to elevated core temperature the sympathetic nervous system signals sent from the POAH to the skin arterioles cause these blood vessels to dilate delivering more metabolic heat to the body surface. Sympathetic nervous system also signals heart to increase heart rate and cause the left ventricle to pump more forcefully.

7. Physiological response to exercise iN heat T he ability to increase stroke volume is limited as blood pools in the periphery and less returns to the left atrium. To maintain cardiac output the heart rate gradually creeps upward to help compensate for the decrease in stroke volume. This phenomenon is cardiovascular drift.

8. Body fluid balance: sweating The eccrine sweat gland are controlled by the stimulation of the POAH. They are located over most of the skin surface with 2 to 5 million covering the whole body. Most densely distributed over palms of hands, soles of feet and the forehead. A second type of sweat gland the apocrine gland is clustered in regions of the body including the face, axilla and genital regions. This are mainly associated with nervous perspiration and has nothing to contribute to heat loss by evaporation.

9. Body fluid balance: sweating Sweat is formed in the coiled secretory portion of the sweat gland and at this stage has an electrolyte composition similar to that of blood since plasma is the source of sweat formation As this filtrate of plasma passes through the uncoiled duct of the gland sodium and chloride are reabsorbed back in to surrounding tissues and blood Final sweat that is extruded onto the skin is hypotonic to plasma.

10. Body fluid balance: sweating While performing exercise in hot conditions the body can lose more than 1 L of sweat per hour per square meter of body surface. A high rate of sweating maintained for prolonged time ultimately reduces blood volume. This limits the volume of blood returning to heart, increasing heart rate and eventually decreasing cardiac output which in return reduces performance potential. Loss of both electrolytes and water in the sweat triggers the release of both aldosterone and antidiuretic hormone called vasopressin.

11. Body fluid balance: sweating Aldosterone is responsible for maintaining appropriate sodium concentrations in blood and ADH maintains fluid balance. During acute exercise in heat and during repeated days of exercise in heat this hormone limits sodium excretion from the kidneys. More sodium is retained by the body so promotes more water retention. Also water reabsorption is stimulated in kidneys by reducing loss of urine frequency. Thus loss of electrolytes and water is compensated during heat stress and heavy sweating. In this way body responds to additional exposures to heat and sweat losses.

12. What limits exercise in heat ?? Any factor that tends to overload the CVS or to interfere with the heat dissipation can drastically impair performance. Another theory that explains limitations to exercise in the heat is the critical temperature theory. This theory proposes that regardless of the rate at which the core temperature increases the brain will send signals to stop exercise when some critical temperature is reached beyond 40̊ C

13. Health risks during exercise in heat Factors that influence the degree of heat stress that a person experiences: Metabolic heat production Air temperature Humidity Air velocity Radiant heat sources Clothing

14. Heat related disorders HEAT CRAMPS It is characterized by severe and painful cramping of large skeletal muscles. Involves muscles that are most heavily used during exercise. Heat cramps are brought on by sodium losses and dehydration that accompany high rates of sweating. Can be minimized by proper hydration, salt intake with foods and in beverages consumed during exercise once occurred move individual to a cooler location, administer saline solution .

15. Heat related disorders H EAT EXHAUSTION (signs and symptoms) Extreme fatigue Dizziness Nausea Vomiting Fainting Weak rapid pulse

16. Heat related disorders Causes: It is caused by CVS inability to adequately meet the bodys needs as it is severely dehydrated. Simultaneous demands of skin and active muscles for blood volume are not met. Excessive fluid loss due to profuse sweating.

17. Heat related disorders Treatment: Rest in a cooler environment Elevation of feet to facilitate return of blood flow Salt water

18. Heat related disorders Heat stroke It is caused by failure of bodys thermoregulatory mechanisms. Increase in internal body temperature to a value exceeding 40 degree Celsius. Confusion, disorientation or unconsciousness Altered mental status Cessation of active sweating If left untreated progresses to coma and finally death

19. Heat related disorders Treatment cooling of body by immersing body in ice or cold water except head Ice bags on arm pits, neck, groin Wrapping body in wet sheets

20. Preventing hyperthermia to prevent heat disorders Schedule practices in early morning and late evening Schedule drink break every 15 to 30 min Appropriate clothing Wear hats

21. Effects of heat acclimation Rapid improvement in the ability to maintain cardiovascular function and eliminate excess body heat is called heat acclimation. Involves changes in plasma volume, cardiovascular function, sweating and skin blood flow Series of positive adaptations takes a period of 9 to 14 days of exercise in the heat. In the first three days expansion of plasma volume occurs Expansion of blood volume More even distribution of sweat over body and more diluted that is sodium conserving End exercise heart rate and core temperature decreases early.

22. Exercise in the cold Peripheral vasoconstriction : occurs as a result of sympathetic stimulation of smooth muscle layers of skin arterioles Stimulation cause smooth muscle to contract, constricts arterioles, reduces blood flow and minimizes heat loss. Non shivering thermogenesis: when changing skin blood flow alone is not adequate to prevent heat loss, there is stimulation for increase in metabolism by SNS and heart rate increases. Shivering thermogenesis: rapid involuntary cycle of contraction and relaxation which can cause increase in bodys rate of heat production.

23. Acclimation to cold People who are regularly expose to repeated cold stress undergo cold habituation in which vasoconstrictor and shivering responses are blunted and core temperature falls to a greater extent. This pattern of adaptation occurs when small areas such as hands and face are exposed repeatedly to cold air. When heat loss occurs at a faster rate; increased metabolic heat production can minimize heat loss and enhanced non shivering and shivering thermogenesis develop called metabolic acclimation.

24. Acclimation to cold Insulative acclimation tends to occur when enhanced metabolism is unable to maintain core temperature. Enhanced skin vasoconstriction occurs Increased peripheral insulation Minimizes heat loss

25. Factors affecting body heat loss Body size and composition: inactive peripheral muscles and subcutaneous fat are excellent insulators. Wind chill: it is an index based on the cooling effect of wind It is typically presented in the charts showing combinations of air temperature and wind speed that result in same cooling power as seen with no wind. As wind chill increases, so the risk of freezing of tissues.

26. Physiological response to exercise in cold MUSCLE FUNCTION: cooling a muscle cause it to contract with less force Muscle fiber recruitment pattern gets altered Muscle velocity and power decreases Decrease efficiency of muscle action Seen more in small muscles than in large

27. Physiological response to exercise in cold METABOLIC RESPONSE: hypoglycemia suppresses shivering Muscle glycogen is used at higher rate

28. HEALTH RISKS DURING EXERCISE IN THE COLD Hypothermia Rectal temperature decreases from normal level Hypothalamus loses its ability to regulate body temperature Cooling may influence SA node activity, hearts pacemaker leading to decease in heart rate Treatment: dry clothing, blankets for insulation, warm beverages

29. HEALTH RISKS DURING EXERCISE IN THE COLD Frost bite Exposed skin can freeze when its temperature is lowered few degrees below freezing point. Tissues die due to lack of oxygen and nutrients. Leads to gangrene and loss of tissue Frostbitten parts are left untreated until they can be thawed without risk of refreezing.

30. HEALTH RISKS DURING EXERCISE IN THE COLD Exercise induced asthma drying of airways due to combination of high respiration with exercise and dry air as temperature drops Narrowing of airways Gasping for breath Corticosteroids and bronchodilators

31. Exercise and sport performance at altitude Maximal oxygen uptake and endurance activity: Decreases as altitude increases until the atmospheric PO2 drops below 131mmHg Decreased vo2max Decreased cardiac output This decline begins at 5000ft

32. Exercise and sport performance at altitude Anaerobic sprinting, jumping and throwing activities: Anaerobic activities are not impaired because they place minimal oxygen demands and on metabolism Thinner air at altitude provides less resistance to athletes movements

33. Acclimation to altitude when people are expose to altitude for days weeks and months their bodies gradually adjust to lower partial pressure in the air But can never fully compensate for hypoxia Three weeks are needed for full acclimation at moderate altitude All of these benefits are lost within a month of return to sea level

34. Acclimation to altitude Pulmonary adaptation: within 3 to 4 days increase in pulmonary ventilation both at rest and during exercise Submaximal exercise ventilator rate plateaus Blood adaptation: during first two weeks number of circulating erythrocytes increases lack of oxygen stimulates the renal release of erythropoietin plasma volume and cardiac output increases with acclimatization Polycythemia is evident for 3 months or more

35. Acclimation to altitude Muscle adaptations: muscle fibre cross sectional area decreased Capillary density in the muscle is increased to allow more blood and oxygen to deliver Decrease in mass and inability to generate ATP at high altitude and thus unable to meet exercise demands Mitochondrial and glycolytic enzyme activity of leg muscle reduced after 4 weeks

36. Cardiovascular response to altitude blood volume Cardiac output Metabolic responses Nutritional needs Muscular adaptations

37. Health risks at altitude Mountain sickness( acute altitude sickness): Nausea, vomiting, dyspnea and insomnia. Symptoms begin after 6 to 48hrs and severe on 2 and 3 days Continous and throbbing Worse in the morning Due to dilation of cerebral blood vessels, so stretching of pain receptors is the likely cause Inability to sleep due to chyenes stokes breathing

38. Health risks at altitude TREATMENT: Gradually ascend to altitude Acetazolamide a day before ascent High flow oxygen Use of hyperbaric rescue bags

39. Health risks at altitude High altitude pulmonary oedema : accumulation of fluid in the lungs pulmonary vasoconstriction occurs from hypoxia Blood clots are formed in the lungs Tissues become overperfused Fluid and protein leaks out of capillaries Fluid accumulation interfers with air movement into and out of lungs Shortness of breath impairs blood oxygenation and cause cause cyanosis

40. Health risks at altitude Persistent cough Chest tightness Excessive fatigue Treated via supplemental oxygen and moving to lower altitude

41. Health risk at altitude High altitude cerebral oedema : fluid accumulation in cranial cavity Mental confusion Lethargy Ataxia Unconsciousness Complication of HAPE

42. Thank you…..!!!