FISIOLOGI SENAM Temperature regulation

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FISIOLOGI SENAM Temperature regulation

  1. 1. © 2007 McGraw-Hill Higher Education. All rights reserved. Chapter 12 Temperature Regulation EXERCISE PHYSIOLOGY Theory and Application to Fitness and Performance, 6th edition Scott K. Powers & Edward T. Howley
  2. 2. © 2007 McGraw-Hill Higher Education. All rights reserved. Objectives • Define tem homeotherm • Present an overview of heat balance during exercise • Discuss the concept of “core temperature” • List the principle means of involuntarily increasing heat production • Define four processes by which the body can lose heat during exercise • Discuss the role of hypothalamus as the body’s thermostat
  3. 3. © 2007 McGraw-Hill Higher Education. All rights reserved. Objectives • Explain the thermal events that occur during exercise in both a cool/moderate and hot/humid environment • List physiological adaptations that occur during acclimatization to heat • Describe physiological responses to a cold environment • Discuss physiological changes that occur in response to cold acclimatization
  4. 4. © 2007 McGraw-Hill Higher Education. All rights reserved. An Overview of Heat Balance • In order to maintain a constant core temperature, heat loss must match heat gain • Thermal gradient from body core to skin surface Fig 12.1
  5. 5. © 2007 McGraw-Hill Higher Education. All rights reserved. Temperature Measurement During Exercise • Deep-body (core) temperature – Thermocouples or thermistors – Rectum, ear, and esophagus • Skin temperature – Thermistors at various locations – Calculate mean skin temperature
  6. 6. © 2007 McGraw-Hill Higher Education. All rights reserved. Heat Production • Voluntary – Exercise • Involuntary – Shivering – Action of hormones • Thyroxine • Catecholamines Fig 12.2
  7. 7. © 2007 McGraw-Hill Higher Education. All rights reserved. Heat Loss • Radiation – Transfer of heat via infrared rays – No physical contact between surfaces – 60% heat loss at rest • Conduction – Heat loss due to contact with another surface
  8. 8. © 2007 McGraw-Hill Higher Education. All rights reserved. Heat Loss • Convection – Form of conductive heat loss – Heat transferred to air or water • Evaporation – Heat transferred via water (sweat) on skin surface – Evaporation rate depends on: • Temperature and relative humidity • Convective currents around the body • Amount of skin surface exposed – 25% heat loss at rest • Most important means during exercise
  9. 9. © 2007 McGraw-Hill Higher Education. All rights reserved. Heat Exchange During Exercise Fig 12.3
  10. 10. © 2007 McGraw-Hill Higher Education. All rights reserved. The Hypothalamus: The Body’s Thermostat • Increased core temperature – Anterior hypothalamus – Commencement of sweating – Increased skin blood flow • Cold exposure – Posterior hypothalamus – Increase heat production • Shivering – Decrease heat loss • Decreased skin blood flow
  11. 11. © 2007 McGraw-Hill Higher Education. All rights reserved. Responses to Heat Stress Fig 12.4
  12. 12. © 2007 McGraw-Hill Higher Education. All rights reserved. Responses to Cold Stress Fig 12.5
  13. 13. © 2007 McGraw-Hill Higher Education. All rights reserved. Heat Exchange During Exercise • Metabolic energy (heat) production stimulates heat loss – Evaporative heat loss • Most important means of heat loss – Convective heat loss • Small contribution – Radiative heat loss • Small role in total heat loss
  14. 14. © 2007 McGraw-Hill Higher Education. All rights reserved. Heat Exchange During Exercise Fig 12.6
  15. 15. © 2007 McGraw-Hill Higher Education. All rights reserved. Body Temperature Increase During Exercise • Increase in body temperature with work rate – Linear across wide range of temperatures – Linear for both arm and leg exercise • Temperature proportional to active muscle mass
  16. 16. © 2007 McGraw-Hill Higher Education. All rights reserved. Body Temperature During Arm and Leg Exercise Fig 12.7
  17. 17. © 2007 McGraw-Hill Higher Education. All rights reserved. Heat Exchange During Exercise Effect of Ambient Temperature • As ambient temperature increases, – Heat production remains constant – Lower convective and radiant heat loss – Higher evaporative heat loss
  18. 18. © 2007 McGraw-Hill Higher Education. All rights reserved. Heat Exchange During Exercise Effect of Ambient Temperature Fig 12.8
  19. 19. © 2007 McGraw-Hill Higher Education. All rights reserved. Heat Exchange During Exercise Effect of Exercise Intensity • With increased exercise intensity – Heat production increases – Higher net heat loss • Lower convective and radiant heat loss • Higher evaporative heat loss
  20. 20. © 2007 McGraw-Hill Higher Education. All rights reserved. Heat Exchange During Exercise Effect of Exercise Intensity Fig 12.9
  21. 21. © 2007 McGraw-Hill Higher Education. All rights reserved. Exercise in Hot/Humid Environments • Inability to lose heat – Higher core temperature – Higher sweat rate • Can result in: – Impaired performance – Hyperthermia
  22. 22. © 2007 McGraw-Hill Higher Education. All rights reserved. Core Temperature and Sweat Rate During Exercise in Heat/Humidity Fig 12.10
  23. 23. © 2007 McGraw-Hill Higher Education. All rights reserved. Heat Acclimatization • Increased plasma volume • Earlier onset of sweating • Higher sweat rate • Reduced sodium chloride loss in sweat • Reduced skin blood flow
  24. 24. © 2007 McGraw-Hill Higher Education. All rights reserved. Exercise in a Cold Environment • Enhanced heat loss – Reduces chance of heat injury – May result in hypothermia • Cold acclimatization – Improved ability to sleep in the cold – Increased nonshivering thermogenesis – Higher intermittent blood flow to hands and feet – Results in ability to maintain core temperature
  25. 25. © 2007 McGraw-Hill Higher Education. All rights reserved. Chapter 12 Temperature Regulation

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