Lecture 9 (Environmental Physiology)

8/12/2019 Lecture 9 (Environmental Physiology)

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(c) 2004 The McGraw-Hill Companies, Inc. All rights reserved.

Objectives

Describe the changes in atmospheric pressure, air temperature,

and air density with increasing altitude

Describe how altitude affects sprint performances and explain

why that is the case

Explain why distance running performance decrease at altitude

Draw a graph to show effect of altitude on VO2 MAXand list

reasons for this response

Graphically describe effect of altitude on the HR and ventilation

responses to submaximal work, and explain why these changes

are appropriate


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Objectives

Describe the process of adaptation to altitude, and the degree to

which this adaptation can be complete

Explain why such variability exists among athletes in the

decrease in VO2 MAXupon exposure to altitude, the degree of

improvement in VO2 MAXat altitude, and the gains made uponreturn to sea level

Describe potential problems associated with training at high

altitude and how one might deal with them

Explain the circumstances that caused physiologists to

reevaluate their conclusions that humans could not climb MountEverest without oxygen


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Objectives

List the factors influencing hypothermia

Explain what Windchill Index is relative to

heat loss Explain why exposure to cold water is more

dangerous than exposure to air of the

same temperature


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Objectives

Describe the role of subcutaneous fat andenergy production in the development ofhypothermia

List the steps to follow to deal withhypothermia

Explain how carbon monoxide can

influence performance, and list the stepsthat should be taken to reduce the impactof pollution on performance


7/30(c) 2004 The McGraw-Hill Companies, Inc. All rights reserved.

Altitude

Atmospheric pressure

Decreases at higher altitude

Partial pressure Same percentages of O2, CO2, and N2in the

air

Lower partial pressure of O2, CO2, and N2

Hypoxia: low PO2(altitude)

Normoxia: normal PO2(sea level)

Hyperoxia: high PO2



Effect of Altitude onPerformance

Short-term anaerobic performance

Lower PO2at altitude should have no effect of

performance

Lower air resistance may improve performance

Long-term aerobic performance

Lower PO2results in poorer aerobic

performance



Effect of Altitude on VO2max

Decreased VO2maxat higher altitude

Up to moderate altitudes (~4,000m)

Decreased VO2maxdue to decreased arterialPO2

At higher elevations

Rate of VO2maxreduction also due to fall in

maximum cardiac output



Changes in VO2maxWithIncreasing Altitude

Fig 24.1


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Effect of Altitude onSubmaximal Exercise

Elicits higher heart rate

Due to lower oxygen content of arterial blood

Requires higher ventilation Due to reduction in number of O2molecules

per liter of air


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Effect of Altitude on SubmaximalHeart Rate Response

Fig 24.2


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Effect of Altitude on SubmaximalVentilation Response

Fig 24.3


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Adaptation to High Altitude

Production of more red blood cells

Counter desaturation caused by lower PO2

In those who grew up at altitude Have complete adaptations in arterial oxygen

content and VO2max

In those recently arriving at altitude

Adaptations are less complete


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Training for Competition at Altitude

Effect of training at altitude on VO2maxvaries betweenathletes

Due to degree of saturation of hemoglobin

Some athletes can improve VO2max

by training ataltitude, others cannot

May be due to training state before arriving ataltitude

Some athletes have higher VO2maxupon return to low

altitude, while others do not Could be due to detraining effect

Cannot train as intensely at altitude


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The Quest for Everest

Mount Everest was climbed without oxygen

in 1978

Previously thought that VO2max

at summit

would be just above rest

Actually, VO2maxestimated at 15 mlkg-1min-1

Due to miscalculation of barometric pressure at

summit


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Challenges ofHigh Altitude Climbing

Successful climbers have great capacity for

hyperventilation

Drives down PCO2and H+in blood

Allows more O2to bind with hemoglobin at

same PO2

Climbers must contend with loss of appetite

Results in loss of weight

Reduction muscle fiber diameter


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Heat

Hyperthermia

Elevated body temperature

Heat-related problems Heat syncope

Heat cramps

Heat exhaustion

May require medical attention

Heat stroke

Medical emergency


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Factors Affecting Heat Injury

Fig 24.6


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Consideration for Exercise

Know signs/symptoms of heat illness

Exercise in cooler part of the day

Gradually increase exposure to heat toacclimatize

Drink water before, during, and after

exercise

Wear light clothing

Alter exercise intensity to stay within THR

zone


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Implications for Performance

Safety during events in high heat/humidity

Time of day, season of the year

Frequent water stops

Traffic control

Identification of those with heat illness

Coordinate proper treatment

First aid, ambulance services, hospitals


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Cold

Important to protect against heat loss Maintain core temperature

The windchill index Describes how wind lowers the effective

temperature at the skin

Water

Causes heat loss by convection 25 timesgreater than in air


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Hypothermia Insulating factors Subcutaneous fat

Clothing

Amount of insulation required is lowerduring exercise

Environmental factors Temperature

Vapor pressure Wind

Water immersion

Energy production


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Insulation in the Cold

Insulation Subcutaneous fat

Clothing

Amount of insulation needed is lowerduring exercise

Energy production increases uponexposure to cold Inverse relationship between VO2and

body fatness

Women cool faster than men


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Factors Affecting Hypothermia

Fig 24.9


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Effect of WaterTemperature on Survival

Fig 24.9


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Changes in

InsulationRequirement atDifferentTemperaturesand Activities

Fig 24.10


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Air Pollution

Ozone

Decreases VO2maxand respiratory function

Sulfur dioxide

Causes bronchoconstriction in asthmatics Carbon monoxide

Binds to hemoglobin and reduces oxygen transport

Prevention of problems

Reduce exposure time Stay away from bolus amounts of pollutants

Exercise during least polluted part of day

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Lecture 9 (Environmental Physiology)