environment and exercise. labs due next week choose to: –take book home and write up lab 5 get...
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Environment and Exercise
Labs due next week
• Choose to:– Take book home and write up lab 5
• Get marks for labs 1-5
– Submit on the day of your lab• Get marks for labs 1-4
Thermoregulation
Body temperature
• Different temperatures:– Surface / Skin– Core body– Tympanic– Esophogeal– Rectal– oral
Regulation
• Regulated by hypothalamus to within 1 degree (37 + or – 1)
• Negative feedback loopThermal receptors in the skin Temperature changes in blood
Mechanisms of Heat Conservation
Mechanisms of Heat Conservation
• Vascular adjustments– Vasoconstriction of
peripheral blood vessels
• Muscular activity– Voluntary physical
activity– Shivering
• Hormonal output– Increased secretion of E,
NE, thyroxine
Mechanisms Facilitating Heat Loss
Mechanisms Facilitating Heat Loss
• Circulatory adjustments
• Evaporation
• Hormonal adjustments
Circulatory AdjustmentsCirculatory 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
Mechanisms of Heat LossMechanisms of Heat Loss• Radiation
– The release of heat via electromagnetic heat waves
• Conduction– Direct transfer of heat through a
liquid, solid, or gas
• Convection– Facilitates heat loss by conduction
by carrying heat away in air currents
• Evaporation– Provides the major physiologic
defense against overheating
Evaporation depends on
• Surface exposed to environment
• Temperature and humidity of air
• Convective air currents
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
Exercise in the Heat
Consequences of DehydrationConsequences of Dehydration
• Reduced plasma volume
• Increased submaximal heart rate
• Reduced rate of sweating
• Impaired ability to thermoregulate
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
Acclimatisation to heat
• Physiologic adaptive changes that improve heat tolerance– Lower Heart rate– Lower skin temp– Lower core body temp
during exercise
Acclimatisation• 2-4 hours each day for
10 days– Efficient blood flow from
core vasodilation conduction
– Sweat• Double sweating capacity
(volume), • Greater area of the body is
used for sweating• More dilute
– Sweat response earlier in exercise session
Factors Affecting Heat Tolerance
Factors Affecting Heat Tolerance
• Acclimatisaton
• Exercise training
• Age
• Gender
• Body composition
• Hydration
Exercise in the Cold
Exercise in water in the cold
• Body loses heat 2 x as fast in cool water as in air the same temperature
Shivering
• Swimming in 18degrees as opposed to 26 degrees = 500 ml/min
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
Evaluating cold stress
• Air Temperature• Wind Chill Index
• Tingling & numbness fingers and toes
• Burning sensation – nose & ears
Acclimatisation to cold
• Genetic- Eskimo
• Repeated exposure of extremities to cold increased peripheral blood flow to reduce possibility of frostbite
Exercise in Pollution
Beijing olympics
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
Amounts
• Carbon Monoxide (COHb) - 2.5 -3 %• Sulfur oxides (Sox), Submax- 1-3 ppm • Nitrogen dioxide (NO2) - 200 to 4,000 ppm = death • Ozone (O3) Submaximal - 0.3 to 0.45 ppm =
decrements in pulmonary function and discomfort• Ozone has also been associated with eye irritation,
general respiratory discomfort and nausea.
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
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
Exercise and AltitudeExercise and Altitude
Exercise at AltitudeExercise at Altitude
– Reduced barometric pressure
– Reduced partial pressure of oxygen (Po2)
– Reduced relative humidity
– Reduced ambient temperature
Acclimatisation
• Adaptive responses to improve one’s tolerance to altitude
• 2 weeks to adapt to 2300 m
• Additional 610 m = 1 week
Immediate Adjustments to altitude above 2300 m
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
• 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
Longer-Term AdjustmentsLonger-Term Adjustments
Long term
• Hematological changes– Reduction in plasma volume – Increase in red blood cell production
(Polycythemia)• Due to erethropoietin released by the kidney
increase in blood’s oxygen carrying capacity
Longer-Term Adjustments Longer-Term Adjustments
• Cellular adaptations– Peripheral changes that facilitate aerobic
metabolism• increased capillary density• Increased mitochondrial densities- increases ability
to store O2 in muscles
Exercise Capacity at AltitudeExercise 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
Altitude TrainingAltitude Training
• Altitude 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
SummarySummary
• Environment critical to optimal performance
• Be aware of environment in case of negative effects
• Use to your advantage– Heat
• Humidity
– Cool– Pollution– Altitude