1. Environment and Exercise

2. Thermoregulation
Humans are homeothermic- we can regulate our own body temp!

3. Body temperature Different temperatures: Surface / Skin Core body
Tympanic
Esophogeal
Rectal
oral
Neg feedback loop
Different temperatures:
Skin- lowest temp
Core body- highest temp
Tympanic- ear
esophogeal

4. Delicate balance between the processes that generate heat and those that dissipate it.
Heat is produced from pretty much every physiological by product- is a by product of many reactions

5. Regulation Regulated by hypothalamus to within 1 degree (37 + or – 1)
Fig 11.5 a and b pg 258, 259
Negative feedback loop
Thermal receptors in the skin
 Temperature changes in blood
Neg feedback loop
Like thermostat in house- except that the body cannot shut off the heat, it has to initiate responses to heat or cold in order to maintain body temperature
Body tells what the temp is from:
Thermal receptors in the skin provide peripheral input to the hypothalamic central control centre
Temperature changes in blood that perfuses the hypothalamus directly stimulate the hypothalamic central control center

6. Mechanisms of Heat Loss/gain
Radiation
The release of heat via electromagnetic heat waves
Conduction
Direct transfer of heat through contact with a liquid, solid, or gas
Convection
Carrying heat on air currents
Evaporation
Provides the major physiologic defense against overheating
Radiation- Primary method for discharging heay only works for cooling the body when the outside temp is cooler than the body temp. “Radiating heat from 5cm away on an exercising person. Also we gain heat via radiation from the sun- that is why standing in the sun is noce and warm but standing in the shade is not!
Conduction- blood is the conductor- as the blood from the working muscles passes through the cooler vessels near pinky or whatever, it is cooled. Also if you put something cold onto your skin = conduction of your heat to the cold thing until equilibrium. Same with a warm thing- Hot water bottle/ blanket!
Convection- air currents- basically, if cool air is next to the body, heat may be lost by conduction, having fan on
Evaporation- 1L sweat = 2428 kj or 580 calories of heat energy body to environment
Have 2-4 million sweat glands
Sweat is % NA CL (Salt)
Clothing resists ability to lose heat from evaporation- which is why you generally want to tear off your shirt when you are exercising!
High humidity also decreases sweating efficiency
Increased room temp decreases effectiveness of all but evaporation

7. If proper mechanisms were not in place, body temp (which increases metabolic rate times that at rest) could increase core body temperature by 1 degree every 5 minutes

8. Primary mechanisms?? At rest? During exercise??
Who has done their reading?
Can you tell me which of those 4 is used more frequently when at rest??
Radiation
And during exercise??
Evaporation. 80% of heat loss during exercise

9. Mechanisms of Heat Conservation
Vascular adjustments
Vasoconstriction of peripheral blood vessels
Muscular activity
Voluntary physical activity
Involuntary- Shivering
Hormonal output
Increased secretion of E, NE, thyroxine
What do you do when you are cold? Show me!
2 ways about it – decrease heat loss and increase heat production
Decrease heat loss by vasoconstriction and reducing surface area (curling up in a ball)
Increase heat production by shivering (increases metabolism to 3-5 times resting levels, increased activity and release of neurotransmitters

10. Mechanisms Facilitating Heat Loss
Circulatory adjustments
Evaporation
Hormonal adjustments
Increase heat loss
vasodilation, sweating
Decrease heat production
Decreased activity muscles and neurotransmitters
Heat stress initiates hormonal adjustments to conserve salts and fluid lost in sweat
Vasopressin (antidiuretic hormone or ADH)
Increases water reabsorption in the renal tubules
Aldosterone
Increases reabsorption of sodium in the renal tubules
Reduces the osmolality of sweat produced

11. Circulatory Adjustments
Two competitive cardiovascular demands exist during exercise in the heat
Oxygen delivery to muscles must increase to sustain exercise energy metabolism
Peripheral blood flow to the skin must increase to transport metabolic heat from exercise for dissipation at the body’s surface
Remember the diagram that showed over 80% blood flow going to muscles??
Circulation to muscles takes precedence over temperature regulation, often at the expense of a spiraling core temperature and accompanying health risk

12. Evaporation depends on
Surface exposed to environment
Temperature and humidity of air
Convective air currents
Humidity has greatest impact
Exerts the greatest impact on the effectiveness of evaporative heat loss
Elevations in relative humidity substantially decrease evaporative heat loss
Have a discussion with person next to you how can lleyton increase his evaporation??
is towelling off effective/ in eff in allowing heat loss??
Hinders evaporative cooling

13. Clothing
Cloth traps air next to skin and warms it to provide insulation
However if sweat is not absorbed and drawn away from skin to be kept dry, clothing loses 90% insulating property
Has impact on uniform and clothing choices
Football- almost no SA for evaporation  difficult to allow heat loss

14. Exercise in the Heat

15. Heat
Beijing
Fig 11.6 shows that compared to thermoneutral environments, HR higher SV lower in hot conditions
40-41 degrees- brain sends signals to stop exercise
Fig 11.6 shows that compared to thermoneutral environments, HR higher SV lower in hot conditions
We will do similar experiment, except we will measure temp in ear rather than rectally, and we won’t measure SV either!

16. Sweat loss peaks at ~3 L during intense exercise in the heat
Intense sweating for several hours can induce sweat gland fatigue

17. Consequences of Dehydration
Reduced plasma volume
Increased submaximal heart rate
Reduced rate of sweating
Impaired ability to thermoregulate
Heat + dehydration = v dangerous therefore need 2 ensure adequate hydration
All of these things reduce the capabilities of the body during exercise, and if exercise continues  heat disorders

18. Heat index- convert to degrees celcius
70 = 21; 80 = 26; 90= 32 = =
130 = 54
Heat cramps- due to loss of sodium in sweat and dehydration- avoid by adequate hydration
Heat exhaustion= fatigue, dizziness, nausea, vomiting, fainting, weak rapid pulse etc becos dehydrated, blood plasma volume decreases, therefore don’t have the SV and CO to be able to pump the blood effectively.
Heatstroke- failure of thermoregulatory systems. Body temp >40 degrees celcius, stop sweating, rapid pulse, confusion, disorientation etc

19. hyperthermia Prevention Treatment
Avoid holding competition when temp >28 degrees
Drink fluids before and after and have breaks every mins
clothing
Treatment
Immerse in ice bath/ cold water
Immerse in ice bath/ cold water
=- what does this facilitate? Evaporation, conduction

20. Clothing for the heat Cover as little SA as possible
Loose fitting to allow convective air currents near skin
Wet allows increased evaporation
Colour
Dark = absorbs radiant heat
Light – reflects radiant heat
What uniforms do you have to wear? Do they adhere to these guidelines???

21. Factors Affecting Heat Tolerance
Acclimatisation
Exercise training
Age
Gender
Body composition
Hydration
Acclimatisaton
Exercise training- sweat sooner
Age- Children have lower rate of sweating and higher core temp during heat stress.
Gender- women sweat less than men for the same exercise workload. Due to higher body S.A to mass ratio
Body composition- Heavier people have smaller S.A to mass ratio, & body fat insulates – therefore vulnerable to heat stress
Hydration- dehydrated= less able to thermoregulate

22. Acclimatisation to heat
Physiologic adaptive changes that improve heat tolerance
Training increases heat tolerance
As does 9-14 days of exercising in heat
Lower Heart rate
Lower skin temp
Lower core body temp
Increased plasma volume
Double sweating capacity (volume), Greater area of the body is used for sweating, More dilute
Sweat response earlier in exercise session
during exercise
Start of season etc

23. Exercise in the Cold

24. Cold Physiological Behavioural adjustments Peripheral Vasoconstriction
Non shivering thermogenesis
Shivering
Behavioural adjustments
Huddle
Voluntary movement
Put more clothes on
Exercise indoors
Physiological- in order- ie vasoconstriction is first
Peripheral Vasoconstriction  Sympathetic nervous system stimulates smooth muscle surrounding arterioles reducing blood flow to the extremities of the body, because when blood flows out there, heat is often lost due to conduction/convection. This is why you turn blue when you are cold!
Non shivering thermogenesis- This is where the Sympathetic nervous system tells the body to “put more wood on the fire” stimulates metabolism to generate more heat
Shivering- rapid involuntary contraction and relaxation of skeletal muscles 4 -5 times more heat can be produced
Behavioural adjustments
Huddling- Some guy that was lost in the forest survived the night because he cuddled up to his dog.
Voluntary movement
Put more clothes on
Exercise indoors

25. Exercise in water in the cold
Body loses heat 4 x as fast in cool water as in air the same temperature
Shivering
Swimming in 18degrees as opposed to 26 degrees = 500 ml/min more o2
Body composition, wind chill and water are the three factors affecting body heat loss.
Body fat is basically insulation; wind chill means that heat is being lost by??? convection
Body loses heat 4 x as fast in cool water as in air the same temperature
the result is Shivering
titanic- jack gets in the water to save rose. If the water was 4 degrees celcius he would have lost heat at 3.2 degrees per hour, more if the water was moving around, therefore would have been hypothermic (body heat of 24 degrees) in 4 hours, though I suspect the water was way colder than that if there were icebergs!
Swimming in 18degrees as opposed to 26 degrees = 500 ml/min more oxygen is required to make up for the energy used up by shivering

26. Exercise in the cold
Increased consumption o2 to compensate for that used in shivering
Increased mobilisation FFA’s for fuel
If low blood glucose reduced shivering  reduced temperature
Cold muscle = decreased contractile force
Particularly when fatigued
Large inner muscles insulated and protected
Peripheral muscles  decreased dexterity
Increased mobilisation FFA’s for fuel
If low blood glucose reduced shivering  reduced temperature
So if you are cold and hungry in trouble!
Think of a time when you were trying to exercise in the cold- your legs just don’t feel as effective!
Playing soccer in 5 degrees-dexterity definitely down

27. Dry Mouth
Air is warmed and humidified by the bronchial tract  27/30 degrees
When air is humidified it takes moisture from the respiratory tract
Especially during exercise
Therefore
Dry mouth
Burning throat
Irritation respiratory passages
Air is warmed and humidified by the bronchial tract  27/30 degrees
When air is humidified it takes moisture from the respiratory tract
Especially during exercise; and especially when the air is cold
Therefore
Dry mouth
Burning throat
Irritation respiratory passages

28. Both Air Temperature and Wind Chill Index are used to predict heat stress.
Frostbite at environmental air temp of -29 degrees
Hypothermia =
Unable to thermoregulate below 29.5 degrees
Lethal btwn body temp of 23 and 25 degrees

29. Evaluating cold stress
S/A node in heart slow HR
Frostbite warning signs
Tingling & numbness fingers and toes
Burning sensation – nose & ears
In extreme cold or when the body is exposed to cold for long periods, vasoconstriction as a protective strategy can reduce blood flow in some areas of the body to dangerously low levels.
The combination of cold temperature and poor blood flow can cause severe tissue injury by freezing the tissue.

30. Acclimatisation to cold
Genetic- Eskimo
Habituation- Repeated exposure of extremities to cold  increased peripheral blood flow to reduce possibility of frostbite
Body is much better at adapting to heat than cold
Extremities = fishermen

31. Exercise in Pollution

32. Pollution
Carbon monoxide, sulfur oxides, nitrogen oxides, ozone, peroxyacetyl nitrate, aerosols, soot, dust and smoke
Large particles and highly soluble gases are usually filtered out in nasal passages
The presence of more than one pollutant, or other environmental stressors (e.g. heat, cold and altitude), which is generally the case in most smog conditions, usually has a more powerful effect on the body.
The nose hairs remove large particles and highly soluble gases very effectively (e.g., 99.9 percent of inhaled sulfur dioxide is removed in the nose), but smaller particles and agents with low solubility pass easily.
During exercise, when mouth breathing plays an important role, this air filtration process is much less efficient, and more pollutants reach the lungs. With respect to the short-term effects of pollutants on exercise performance, the main problems are irritation of the upper respiratory tract, respiratory discomfort and reductions in the oxygen transport capacity of the blood. Carbon monoxide (CO) emissions in urban areas are greater than emissions of all other pollutants combined. CO primarily affects exercise performance through its strong (200 times stronger than that of oxygen) capacity to bind to hemoglobin (COHb) in the blood, thereby reducing the blood’s capacity to transport oxygen to the tissues. Very high levels of COHb are needed to produce reductions in submaximal exercise performance. Therefore, under realistic outdoor conditions, the effects of CO only become evident when maximal exercise performance is an issue. For example, maximal oxygen uptake is reduced at COHb concentrations above 4.3 percent (during prolonged exposure to heavy traffic, COHb concentrations of 5 percent have been observed).

33. Effects Irritation of the upper respiratory tract
30 min submax exercise = smoking a pack of cigarettes
Carbon monoxide - reduces the blood’s capacity to transport oxygen to the tissues.
Asthma attacks
Time and dose dependant
With respect to the short-term effects of pollutants on exercise performance, the main problems are irritation of the upper respiratory tract, respiratory discomfort and reductions in the oxygen transport capacity of the blood. Carbon monoxide (CO) emissions in urban areas are greater than emissions of all other pollutants combined.
CO primarily affects exercise performance through its strong (200 times stronger than that of oxygen) capacity to bind to hemoglobin (COHb) in the blood, thereby reducing the blood’s capacity to transport oxygen to the tissues.
Very high levels of COHb are needed to produce reductions in submaximal exercise performance. Therefore, under realistic outdoor conditions, the effects of CO only become evident when maximal exercise performance is an issue. For example, maximal oxygen uptake is reduced at COHb concentrations above 4.3 percent (during prolonged exposure to heavy traffic, COHb concentrations of 5 percent have been observed).

34. Beijing 2008
Pollution levels 2-3 x higher than those deemed safe by WHO
Trial to take 1 million cars off the road to see if pollution levels go down
Several countries have also indicated that their athletes will arrive at the games as late as possible to avoid exposure to pollution.[68] Despite this, Beijing, in its commitment to improving air quality, will remove 60,000 taxis and buses from the roads by the end of 2007 and plans to have relocated 200 local factories, including a prominent steel maker,[66] before the games begin

35. Exercise and Altitude

36. Exercise at Altitude Reduced barometric pressure
Reduced partial pressure of oxygen (Po2)
Reduced relative humidity
Reduced ambient temperature
Same amount of oxygen in the air, it is just that the respiratory process is so heavily reliiant on pressure (Recall, to breathe in ribs go up to increase pressure inside lungs, so air rushes in to equalise the pressure…etc also gradient btwn alveoli and blood means that the diffusion process doesn’t work as effectively.
As altitude increases, partial pressure of oxygen decreases and therefore cannot diffuse into the blood at the rate that is possible at sea level. Fig 12.2
Therefore increased ventilation to try to obtain the same amount of oxygen
Add to this the extremelyt cold air temperature and wind chill, and the fact that there is very little moisture in the air.
Low relative humidity means that there is enhanced evaporation of water from respiration, and skin to air (due to difference in concentration btwn them) and therefore dehydration

37. Immediate adjustments to altitude above 2300 m
Hyperventilation
Chemoreceptors detect that not getting enough oxygen
Increase ventilation to compensate
 evaporation fluids respiratory tract
Cardiovascular
Increased HR and cardiac output
At rest and during submaximal exercise
Compensate for thinner air and reduced alveolar oxygen pressure
Cardiovascular responses occur during submax exercise but cannot be upheld during maximal exercise

38. Comprehensive diagram
Q: Remember back to the first few slides yesterday on how respiration occurs? The diaphragm goes (down) to (increase) the pulmonary volume which (decreases) the pressure to 5 mmHg below atmospheric pressure??
When atmospheric pressure is 550 instead of 950, is a long way to go!  shortness of breath
Also, there is the same amount of oxygen in the air(20.9%) but it is density decreases  arterial hypoxia
Acute exposure to 4300 m reduces aerobic capacity by 32% compared to sea level
If we were able to get helicopters up to the top, and drop you off on the top of everest, as an unacclimatised person you would become unconscious in 30 seconds, however this amount of time can be drammatically increased by acclimatisation

39. Exercise Capacity at Altitude
Aerobic capacity
Progressively decreases as altitude increases
1-3.5% reduction Vo2 max every 300m increase from 1500 m
Greater rate decline for trained athletes
Circulatory factors
Decreased MHR and SV
Reduced Vo2 max, MHR, SV etc means can’t exercise to the same extent

40. Acclimatisation
Adaptive responses to improve one’s tolerance to altitude
2 weeks to adapt to 2300 m
Additional 610 m = 1 week

41. Longer-Term Adjustments
Cellular adaptations
Increased capillary density
Increased mitochondrial densities
Blood volume-
Plasma volume decreases
Erythropoietin released  increase RBC
Acid-base adjustment
Ambient air at altitude contains very little Co2
Affects gradient of o2/Co2 volumes
Combined with hyperventilation causes low Co2  increased pH
Increased mitochondrial densities- increases ability to store O2 in muscles
Ambient air at altitude contains very little Co2
Affects gradient of o2/Co2 volumes
Combined with hyperventilation causes low Co2  increased pH
It is these adjustments that athletes would like to capture to increase their performance at sea level.

42. Altitude Training
Acclimation to altitude improves one’s capacity to exercise at altitude
However inability to train at equivalent intensity no improvement Vo2 max on return to sea level
 Live High, Train Low
Altitude acclimation improves one’s capacity to exercise at altitude
However, the effect of altitude exposure and training on endurance performance at sea level remains equivocal
- Most studies found no increase in Vo2 max on return to sea level
May be due to physiological adaptations that actually negate improvements in oxygen-carrying capacity
3-6 wks would be required to see benefits
Live High, Train Low
Return to lower altitude to train so can maintain intensity
Athletes who lived at 2500 m and trained at 1250 m showed greater performance increases in the 5000-m run than athletes who lived and trained at 2500 m or athletes who lived and trained at sea level

43. Now you don’t have to go anywhere!!
Altitude tents/ portable devices – simulate altitude – use for a few minutes/ few hours

44. Summary Environment critical to optimal performance
Be aware of environment in case of negative effects
Use to your advantage
Heat
Humidity
Cool
Pollution
Altitude