The document discusses the physiological effects of exercising in the heat and strategies for athletes to reduce the impact of heat. It covers acute responses like increased sweating and core temperature. It also discusses performance implications of dehydration and strategies for acclimation like improved sweating and cardiovascular function over 7-14 days. Drinking guidelines are provided to hydrate before, during and after competition with water and electrolytes in hot conditions.

1. APPLIED EXERCISE PHYSIOLOGY -EXERCISE IN THE HEAT

2. Applied Exercise Physiology On completion of this unit a learner should: Know how temperature and altitude affect exercise and sports performance Know about the physical differences between people of different gender and race and their affect on exercise and sports performance

3. 3. Know the impact that the physiological effects of ageing have on exercise and sports performance 4. Know the effects and implications of using ergogenic aids for exercise and sports performance.

5. INTRODUCTION EFFECT OF HIGH TEMPERATURES ON SPORT AND EXERCISE

6. You have evolved over millions of years to exist within a narrow range of Physiological variables From the amount of water in your body, to the acidity in your cells and the concentration of glucose in your blood These are regulated by physiological and hormonal responses to maintain “Optimal” conditions AKA?

7. Exercise and heat exsist to most adult as the biggest CHALLENGE to HOMEOSTASIS

8. Most sports have to compete in change of climate This pushes bodies ability to control its internal environment, this has significant physiological consequences Balance between preventing “hyper” thermia and maintaining an adequate fuel supply to the muscles. This is an abnormally high core temperature, and has significant implications on performance and health.

9. What points where highlighted by the video? http://www.youtube.com/watch?v=ESauS61OHFg

10. HYPOTHALAMUS Temperature is regulated by the hypothalamus Posterior hypothalamus is concerned with heat loss Controls sweating and skin blood flow responses

12. Hypothalamic dysfunction? What do you think the symptoms would be?

13. HEAT Exchange Radiation Convection Conduction Evaporation Hot dry environment 98% of cooling

14. Activity With a partner think of as many acute responses to heat as possible. There are the responses that occur immediately when exposed to the stimulus of heat And responses that take longer to occur

15. ACUTE RESPONSES Acute responses similar to exercise however exacerbated in the heat. Increase Sweat Response (Most obvious) Increase Skin and Muscle vasodilation Increase Core Temperature

16. Accute responses to exercise Increase HR BP Maintenance Takes precedence over skin blood flow Increase Lactate production Changes in Substrate Metabolism

17. CARDIOVASCULAR RESPONSE Progressive decline in Stroke Volume Due to Sweat losses Increase in HR to compensate Attempt to maintain Cardiac Output , progressive loss in Cardiac Output causes a decrease in BP Extreme Cases – BP regulation wins out over temp regulation

18. CARDIOVASCULAR RESPONSE.... When Hyper thermia starts to occur Blood diverted away from the skin Maintain BP IMPLICATIONS Hyperthermia as no evaporative sweat losses Risk of Death

19. SUBSTRATE METABOLISM/ LACTATE PRODUCTION Increase in CHO usage during exercise in the heat Epinephrine (adrenaline) levels increase with exercise in the heat Could result in Increase in Lactate production less ability to oxidise lactate back to pyruvate

20. FLUID LOSS As duration and intensity of exercise increases sweat reponse usually increases? Sweating helps the body lose heat by....? How much you sweat is determined by the temperature your training status

21. FLUID LOSS 2-3L per hour during exercise in the heat Hypo hydration/ Dehydration Lack of fluid intake/sweat rate Dehydration impairs thermoregulation. Leads to… Hyperthermia Inability to use cooling mechanisms in extreme environments may feel dizzy, faint, nauseated, or very thirsty. Same response to losing a lot of blood

22. PERFORMANCE IMPLICATIONS Decreases muscular endurance and max aerobic power Unsure about the effect on anaerobic performance but research suggests no impact if progressive dehydration does not occur before the event.

23. PERFORMANCE IMPLICATIONS Debate over theories Less substrate availability Increased lactate production Suggested critical core temperature Muscle recruitment inhibited during exercise in the heat Tucker (2004) showed power output began to fall within the first 30% of maximal self-paced time trial in the heat. This suggested the decrease in performance was not associated with an altered temperature, heart rate or exercise perception.

25. For next week An athlete comes to you they have been suddenly called up for a outdoor competition in India during the summer temperatures can reach over 40C, they want advice on what they’re drinking strategy should be. How much should they drink? Before competition, during and after? What can they do to maximise fluid retention, is just water enough?

26. PART 2

27. Last weeks question How much should they drink? Before competition, during and after? What can they do to maximise fluid retention, is just water enough?

28. Recap The body defends itself from heat through three mechanisms: breathing, sweating, and changing the blood flow. The first reaction is to circulate blood to the skin, which increases skin temperature and allows the body to give off some heat.

29. During heavy work, muscles need more blood flow, which reduces the amount of blood available to flow to the skin and release the heat. Sweating also helps the body to cool off humidity levels need to be low enough to allow the sweat to evaporate. water and salts lost through sweating must be replaced to keep sweating.

30. Four environmental factors affect the amount of stress an athlete faces in a hot environment area: temperature, humidity, radiant heat (such as from the sun or a furnace) wind speed.

31. Great North Run 2005

32. Four participants died en-route to South Shields Particular deadly set of circumstances occurred, High humidity, High temperatures and prevailing tail wind “ they had all been physically fit and well-prepared for the event.”

33. NUTRITIONALSTRATEGIES Hyper hydration Chronic, with acclimatization Glucose + Water,Gastric Discomfort, urination, Increase body mass Water only Hydration Only replaces 30-70% of sweat losses

34. Rehydration Water ingested -> dilution of plasma osmolarity (reduces the concentration of electrolytes)-> reduced thirst This is why electrolyte and Sodium drinks such as Gatorade and PowerAde are important. CHO Loading Daily intakes 7-10g/kg of BM Avoid caffine and alcohol!

35. IMMEDIATE COMPETITION STRATEGIES TO REDUCE EFFECTS OF HEAT? Athlete or exerciser comes to you complain of feeling to hot before and during exercise or competition what do you do?

36. IMMEDIATE COMPETITION STRATEGIES TO REDUCE EFFECTS OF HEAT Pre Cooling Ice vests Cold air Avoiding getting hot too soon reduces physiological strain Lower Core Temperature Delays dehydration and hyperthermia Clothing Light weight/ little as possible/Compression wear

37. Cooling vest

39. Compression Wear there is evidence to suggest that compression clothing may improve exercise performance by reducing the impact of hot and/or humid conditions on the body’s thermoregulatory system

40. Increases in skin and core temperature and a reduction in cooling efficiency are observed when clothing interferes with the evaporation of sweat from the skin. It has been suggested that compression clothing assists the rate of evaporation faster transfer of sweat from the skin to the fabric.

41. Once there, the sweat can be dispersed more quickly and evenly over a larger area This Allows evaporation to be maximised. Athletes would feel cooler during exercise and perceive the activity as being less difficult.

42. WET BULB GLOBE TEMPERATURE (WBGT) Estimation of heat stress. WBGT accounts for the levels of humidity, radiation, wind movement and ambient temperature WBGT Risk <18 Low 18-23 Moderate 23-28 High >28 Hazardous

43. WBGT Map

44. ACCLIMATISATION Repeated exposures to the heat results in adaptations within the body that make the athlete less susceptible to the demands imposed by exercise in the heat. Heat tolerance is improved Therefore performance in the heat is improved

45. STRATEGIES AND DURATION Conflicting Views Long term/ short term Recent research suggests 7-14 days Major adaptations plateau after 14 days Most of adaptation undertaken 5-6 days Acclimation Training Artificial Environment Same Intensity and duration

46. ADAPTATIONS Response & effect RESPONSE EFFECT Improved skin blood flow Dissipate heat effectively Lower Heart Rate Work at a higher intensity Effective distribution of CO Meet thermoregulation and metabolism demands Reduction in sweating threshold Evaporative cooling begins earlier Increased distribution of active sweat glands Maximizes evaporative cooling Increased sweat rate Maximizes Evaporative Cooling

47. ADAPTATIONS RESPONSE EFFECT Reduction in loss of water and electrolytes from sweat Preserves sodium in extra cellular fluids, promotes water retention Better maintenance of Core Temperature Fatigue delay, increase thermoregulatory capacities Increasing sweating sensitivity to increasing core temp Maximizes Evaporative cooling Less reliant on CHO metabolism CHO sparing, less lactate accumulation ?

48. ADAPTAIONS TO MAINTAIN CORE TEMP Sawka et.al (2000) Core temperature does not rise as quickly Delays onset of dehydration and hyperthermia Thermoregulatory responses carried out as normal for longer

49. BLOOD VOLUME CHANGES Expansion of blood volume. Large shift of blood to the peripheral areas. I.e. decrease in plasma volume. Stimulates increased renal sodium and water retention. Aldosterone and Vasopressin (ADH) released to help mediate expansion.

50. HEART RATE Due to increase in Blood Volume, heart rate decreases rapidly in the first four days of an acclimation program More blood means the heart doesn't have to work as hard The HR still increased during exercise, but at a much slower rate after acclimation. A decrease of about 22BPM from the first day has been shown.

51. SWEATING Sweating rate occurs at a lower core temperature. Rate of sweating increases, more effective evaporative cooling in dry temperatures. Increased distribution of active sweat glands Higher Plasma sodium concentrations allows for greater water retention in the body.

53. Hue et.al (2004) Sweat Rates

54. HOW CAN THIS HELP?? Acclimatisation allows the body to exercise for longer at a higher intensity in the heat Body adapts and delays dehydration and hyperthermia Better thermoregulation Hence, delays onset of fatiguing elements and increases performance capacity.

55. Heat Training practical examples Candian Triathletes training for cancun mexico competition. cram 5 people into remodeled 5th wheeler complete with heaters, filters and various other apparatus crank the heat up to 38c and 80% humidity

56. Canadian Triathlon Team

58. ride for 90min with your core temp at 39 degrees drink as much water as you can handle get sports &quot;data miner&quot; to collect the stats

59. Planning for next week We are in the gym 1 person in each group will be the subject and the subject again the following week We will weigh them before and after exercise in the same clothes first week will be with added clothing so subjects must wear long sleeve top and training bottoms. No compression wear underneath!

60. The week after, either shirtless and only shorts or compression wear. 3 helpers will be on hand for the subject. 1Data collector 1 Minder, to make sure the subject feels ok and ensures they’re drinking enough water 1 time keeper Testers should also wear sensible clothing, no jeans

61. Duration will be 20 minutes moderate intensity level 4 during warm up and then 8 for bikes. 4-6 kph and then 7-9 Kph (avg jogging speed) for treadmill users First 5 minutes will be warm up and last 2 minutes cool down We’ll be measuring weight, measuring RPE, and measuring fluid intake Be sure to bring electrolyte drinks for post test recovery

62. Pay your testing dues If you volunteer to be a subject now it means your less likely be one for future testing If you know what it feels like you will have a greater understand when testing others!