Option A.2 Environmental Factors and Performance

1. Option A.2 Environmental Factors and Performance

2. Environmental Factors and Performance • Production of Heat and Temperature Regulation • Working in Hot Environments • Heat Illness, Capacity and Performance • Working in Cold Environments • Body Response, Body Adaptation, Wind Chill, Cold Water

3. Body Temperature Regulation • Humans are homeothermic • Internal body temperature is physiologically regulated to keep it consistent • Normal Baseline Temperature Range • 36.1- 37.8 Celsius or 97.0 -100.0 Fahrenheit • Regulation works on a careful balance between heat accumulation and heat loss

4. Metabolic Heat Production • Only between 20-25% of energy stored in Adenosine Triphosphate (ATP) is used for muscle contraction. • 75-80% of energy is converted to heat • Heat is produced by all active tissue in the human body • If more heat is produced by the body than can be lost the internal core temperature can rise

5. Core vs. Shell Temperature • Core Temperature (Tc)- temperature deep within the body • Shell Temperature- Temperature near the body surface • Approx 1-6 degrees less than core temp. • Sproules, J Sport, Exercise and Health Science CC

6. Temperature Regulation • Body temp measured through numerous temperature sensors located throughout the body • Hypothalamus- temperature regulation centre in the brain • Detects changes from body sensors and sends messages to the body to respond accordingly

7. Thermoregulation • Heat from the core is moved to the surface of the body through the blood. Heat is transferred to the environment through 4 different mechanisms • Conduction • Convection • Radiation • Evaporation

8. Conduction (K) • Involves transfer of heat from one solid material to another through molecular contact • Ex. Heat loss from the body when skin in contact with a cold object or heat gained if in contact with a warmer object • Prolonged exposure to warm surfaces can increase core body temp. • Conduction accounts for small amount of heat loss (less than 2%)

9. Convection (C) • Transfer of heat by the motion of gas or liquid across the heated surface • Air moves passed us during exercise and heat is exchanged with air molecules • Air cooler than skin convection results in heat loss • Air is warmer than the skin convection results in heat gain • Fact- In cold water heat dissipated through convection can be 26X greater than with air.

10. Radiation (R) • Heat is given off from the body in the form of infrared rays (electromagnetic waves) • Skin radiates heat in all directions to surrounding objects • Temp. around the skin is less radiation leads to a heat loss but if warmer then results in heat gain. • Lighter clothing that increases heat loss • Limit radiant heat absorption and provide max skin exposure

11. Evaporation (E) • Main avenue for heat loss during exercise • Accounts for 80% during exercise and approx 10-20% at rest • Sweat reaches the skin and is converted from liquid to a vapor. Heat loss through vaporization • Evaporation of 1L of sweat results the loss of 680 W (2,428 Kj) of heat

13. Un-Evaporated Sweat • Sweat that drips off the body, soaks into clothing or is wiped off the skin does not contribute to the cooling system • Represents a wasteful loss of body water • Clothing that allows water vapor molecules through will aid in heat loss

14. Heat Balance Equation • Heat Balance can be represented by an equation M-W ± R ±C ±K – E = 0 - If Equation comes out > 0 then heat is stored and core body temp. rises.

15. Humidity and Heat loss • Relative Air Humidity effects the heat loss through evaporation • Dry Air received vaporized sweat more easily • If humidity is high, air already contains water and sweat vapors passed from the skin is decreased • High Humidity limits sweat evaporation and heat loss

16. Exercising in Hot EnvironmentsGroup Extension • You have a group of athletes that will be taking part in a training camp in 30 degree weather • In small groups make recommendations for the athlete that might assist in the removal of heat from the body and decrease the chance of a heat illness. • Provide reasons for your recommendations

17. Acclimation Data 1. Review figure 12.11. What do these two graphs tell us about rectal core temperature, heart rate and exercise rate between acclimated and unacclimated athletes? 2. Review figure 12.12. What to the graphs tell us about temperature, heart rate and hourly sweat rate over a 12 day workout in a hot environment?

18. Physiological Responses to Exercise in Heat

19. Cardiovascular Function • During exercise already a large demand on the cardiovascular system but is increased when there is a need to remove heat • During Exercise two things occur • Further increase in cardiac output • Blood Flow shunted away from non-essential areas (gut, liver, kidneys). Increase amount to muscles and skin

20. Cardiovascular Function and Muscles • The reduced muscle blood flow in high temperatures results in increased glycogen breakdown in the muscle and higher levels of muscle and blood lactate in comparison to the same exercise performed in a cooler environment.

21. Role of the Hypothalamus • Hypothalamus sends message through the sympathetic nervous system • Sends message to skin arterioles to dilate, increasing blood flow • Increase in Heart rate to maintain cardiac output

22. Exercise Capacity and Performance in Hot Environments • Blood Flow to working muscles is relatively well maintained during exercise • Effects blood flow to other areas of the body • Muscle force and activation is reduced • Impaired Mental Activity • Reduced state of arousal and feelings of lethargy

23. Reducing the Effect of Heat Stress • Studies (Skein et al.) have shown that pre-cooling before exercise in heat can delay in heat stress • Could include ice-packed towels • Ice-Baths • Misting Fans

24. Effect on the Brain • “Temperature on the brain is dependent on temperature of the blood that supplies it” • Sproules, J pg. 181 • Cooling the head and neck area during exercise can reduce the temperature of the blood that supplies it • Reduce or delay effects of heat stress

25. Critical Temperature Theory • Theory that proposes that regardless of the rate that core temperature rises, the brain will send signals to stop exercise when some critical temperature is reached • Usually between 40 and 41 degrees (104-105 F) • Kenney, Wilmore, Costill, Physsiology of Sport and Exercise, 5ed.

26. Cold Environments

27. Cold Stress • Cold Stress- any environmental condition causing a loss of body heat that threatens homeostasis • Any change to shell or core temperature sends feedback to the thermoregulatory centre • Signals hypothalamus to activate measurements to conserve body heat

28. Ice Man

29. Physiological Responses to Cold • Body has three primary responses to limit heat loss • Peripheral Vasoconstriction • Non-Shivering Thermogenesis • Shivering

30. Peripheral Vasoconstriction • The constriction or narrowing of blood vessels leading to the periphery • Reduces blood flow to the shell of the body reducing heat loss • First line of defense against decreases in core temperature

31. Non-Shivering Thermogenesis • The stimulation of the metabolism by the sympathetic nervous system to generate more metabolic heat

32. Shivering • A rapid involuntary cycle of muscle contraction and relaxation of skeletal muscles that generates heat • Creates 4-5 fold increases in bodies rate of heat production • Why would shivering cause an increase in the production of heat?

33. Body Size and Composition • Best way to minimize heat loss is through insulation • Resistance to dry heat exchange through conduction, convection and radiation • Peripheral muscles and fat act as excellent insulators to heat loss • Those with more fat do better in colder climates • Maintain temperature before shivering begins

34. Body Size and Composition • Heat Loss also affected by body surface to body mass ratio • Larger individuals have smaller surface area-mass-ratio • Less susceptible to hyperthermia • Children have large surface area-mass ratio • Leads to greater heat loss and more susceptibility to hyperthermia

35. Surface Area-Mass Ratio • Table 12.2. Body Weight, Height, Surface Area, and Surface Area/Mass Ratio for Average-Sized Adults and Ratios • Person Weight (kg) Height (m) Surface Area (m2) Area/Mass Ratio Adult 85 1.83 2.07 0.024 Child 25 1.00 0.79 0.032 Source: Kenney et.al Physiology of Sport & Exercise

36. Gender Differences • In similar size individuals females have better insulation because of greater subcutaneous fat • Males tend to have larger muscle mass • Improve heat production through shivering • Gender differences tend to be minimal

37. Role Review 1. Define Cold Stress  2. Describe the bodies three primary responses to limit heat loss in cold environments  3. Describe reasons why some studies have shown minimal differences in heat retention between men and women.

38. Wind Chill • Windchill- index based on the cooling effects of wind • Air Movement or wind increase convective heat loss, increasing rate of cooling • Windchill is not the temperature of the air • Windchill does not change air temperature • Windchill effects increase the risk of frostbite and hyperthermia

39. Windchill Chart

40. Extension • Pg. 184- To Research • During the same relative sub-maximal exercise intensity in a cold compared to a temperate environment, explain what happens to economy (the rate of oxygen uptake) • Complete the Test Yourself Questions #1-3 pg. 185 • Read Adaptation to chronic cold exposure pg. 185 • Identify and describe three ways one acclimatizes to chronic cold

41. Cold Water Immersion • Respiratory and Cardiac Response to cold water immersion • Tachycardia- resting heart rate greater than 100 beats/min • Hyperventilation- a breathing rate or tidal volume greater than necessary for normal function

42. Heat Loss in Cold Water • Convection allows for the greatest heat loss in cold water • 26 times greater than air • With all heat loss mechanisms, the body loses heat four times faster in water

43. Body Temperature in Cold Water • Human can maintain body temperature when water temperature down to approx. 32 degrees • Colder water temp. may lead to hypothermia • Individuals in water at 15 degrees have a decrease in rectal temp. of about 2.1 degrees per hour • Source: Kenney et al. Physiology of Sport and Exercise

44. Extension • Explain why swimming in cold water represents a particular challenge to the body’s ability to thermoregulate • Discuss in pairs

45. Physiological Responses to Exercise in the Cold

46. Muscle Function • When muscle is cooled contracts with less force • Both shortening velocity and power decrease • Large deep muscles don’t experience heat loss because of location • Small muscles (ex. in fingers) become cold quickly lose dexterity and ability to use fine motor skills • Clothing insulation and exercise metabolism can be enough to offset early temperatures

47. Muscle Function in Endurance Activities • As fatigue kicks in metabolic heat production is reduced • Causes individuals to begin to experience a decline in their core temperature • Depending on temperature can lead to cold illnesses with prolonged exposure

48. Metabolic Responses • Increased Oxygen uptake • Caused by the muscles needs when shivering initiated • During sub-maximal exercise see lower heart rate • Stroke volume increases to maintain cardiac output • Increased central blood supply because of vasoconstriction to the periphery

49. Fuel Utilization • With prolonged exercise carbohydrate stores depleted leading to a decrease in blood glucose levels • Increase utilization of fats, proteins and muscle glycogen • Fuel utilization dependent on duration, intensity of exercise and temperature

50. Asthma and Exercise in Cold Climates • Those with exercised induced asthma, cold environments can lead to shortness of breath and reduced capacity • Strenstrud et. Al found lower oxygen uptake and running speed in individuals in colder climates (-18 compared to 20 degrees)