Presentation Package

1
chapter
12
Exercise at Altitude
2
Learning Objectives

• Find out what conditions in hypobaric
  environments (at altitude) limit physical
  activity
• Learn the physiological adjustments that
  accompany acclimatization to altitude
• Discern whether an endurance athlete who trains
  at altitude can perform better at sea level

3
Conditions at Altitude

• At least 1,500 m (4,921 ft) above sea level
• Reduced barometric pressure (hypobaric)
• Reduced air temperature
• Decreased water vapor pressure
• Increase in solar radiation intensity

4
Differences in Atmospheric Conditions at Sea
Level up Through an Altitudeof 9,000 m (29,520
ft)
5
High Altitude Environments

• Key Points
• Altitude represents a hypobaric environment
• Percentages of gases remain constant but the
  partial pressures of the gases decrease
• Air at altitude is dry
• Because the atmosphere is thinner and drier,
  solar radiation is more intense, which is
  magnified by snow cover

6
Reductions in PO2 and Endurance Performance

• The reduction in PO2 at altitude affects the
  partial pressure gradient between the blood and
  the tissues and thus oxygen transport. This
  explains the decrease in endurance performance at
  altitude.

7
Cardiovascular Responsesto Altitude Cardiac
Output

• Cardiac output is increased at rest and during
  submaximal exercise
• Acute exposure results in a decrease in stroke
  volume and an increase in heart rate
• Increase in HR and cardiac output peaks after
  6-10 days at altitude

8
Metabolic Responses to Altitude

• Basal metabolic rate increases
• Increased thyroxin and catecholamines
• Acute decline in appetite
• Increased reliance on carbohydrates for fuel at
  rest and during exercise
• Lactate paradox

9
Cardiovascular Responses to Altitude

• Key Points
• There is a decreased PO2 throughout the body
• With acute altitude exposure, pulmonary
  ventilation increases, pulmonary diffusion is
  maintained, but oxygen transport is slightly
  impaired
• Oxygen uptake by the muscle is impaired due to a
  reduced diffusion gradient
• Initially, decreased plasma volume increases red
  blood cell concentration, allowing more O2 to be
  transported per unit of blood

(continued)
10
Cardiovascular and Metabolic Responses to
Altitude (continued)

• Key Points
• Initially, cardiac output during submaximal work
  increases to compensate for decreased O2 content
  through an increase in heart rate
• During maximal work, stroke volume and heart rate
  are lower, resulting in decreased cardiac output
• Oxygen delivery and uptake are impaired
• Metabolic rate increases by increased sympathetic
  nervous system activity
• Increased reliance on carbohydrates for fuel
  during rest and exercise

11
Changes in Maximal Oxygen Uptake With Decrements
in Barometric Pressure and Partial Pressure of
Oxygen

• Data from E.R. Buskirk et al., 1967, "Maximal
  performance at altitude and on return from
  altitude in conditioned runners," Journal of
  Applied Physiology 23 259-266.

12
Anaerobic Sprinting, Jumping,and Throwing
Activities

• Anaerobic sprint activities lasting less than a
  minute or two are not impaired
• Sprinting, jumping, and throwing activities might
  be improved due to the thinner air and less
  aerodynamic resistance to movement

13
Exercise and Sport Performance at Altitude

• Key Points
• Prolonged endurance performance suffers the most
  at high altitude because oxidative energy
  production is limited
• VO2max decreases in proportion to the decrease in
  atmospheric pressure
• Anaerobic sprint activities lasting lt 2 minutes
  are not impaired at moderate altitude
• Sprinting, jumping, and throwing activities might
  be improved due to the thinner air and less
  aerodynamic resistance to movement

.
14
Acclimatization to Altitude Pulmonary and Blood
Adaptations

• Pulmonary adaptations
• The increased resting ventilation rate levels off
  at a value 40 higher than at sea level
• Submaximal exercise ventilation rate plateaus at
  50 higher
• Ventilation during exercise remains elevated at
  altitude and is more pronounced at higher
  intensities
• Blood adaptations
• ? Number of red blood cells, polycythemia
• ? Plasma volume
• ? Hemoglobin content
• ? Oxygen-carrying capacity

15
Hemoglobin (Hb) Concentrationsof Men Living at
Various Altitudes
16
Acclimatization to Altitude Muscle and
Cardiovascular Adaptations

• Muscle adaptations
• Decrease in muscle fiber cross-sectional area and
  total muscle
• Reduced mitochondrial and glycolytic enzyme
  activities
• Increased capillary supply
• Cardiovascular adaptations
• Decrease in VO2max with initial exposure and does
  not improve with continued exposure

.
17
Acclimatizationto Altitude Adaptations

• Key Points
• Hypoxic conditions stimulate red blood cell
  production
• Overall there is an increase in total blood
  volume and an increase in oxygen-carrying
  capacity
• Muscle mass and total body weight decrease as a
  result of dehydration, appetite suppression, and
  protein breakdown in muscles
• Muscle adaptations include decreased fiber area,
  increased capillary supply, and decreased
  metabolic enzyme activities
• Work capacity improves but the decrease in VO2max
  does not improve

.
18
Altitude Training for Sea-Level Performance

• Increases red blood cell mass on return to sea
  level
• Existing research does not support the assertion
  that altitude training improves sea-level
  performance
• Difficult to study since intensity and volume of
  training are reduced at altitude
• Live at moderate altitudes and train at low
  altitudes, where training intensity is not
  compromised

19
Living High, Training Low
Improvements in race time in elite male and
female runners and college male and female
runners following four weeks of living at
altitude but training at 1,250 m
20
Training for Optimal Altitude Performance

• Compete within 24 hours of arrival at altitude
• Train at 1,500 to 3,000 m above sea level for a
  minimum of 2 weeks before competing
• Increase VO2max at sea level to be able to
  compete at a lower relative intensity

.