Exercise at Altitude
Who performs better at a bike
race in San Francisco… the
athlete who trains at altitude, or
the athlete who trains sea level?
Why?
How high is high?
• Moderate = <12,000 ft
• High = 12,000 to 18,000 ft
• Very High = >20,000 ft
Stress of Altitude
• The 4 “H”s
– Hypoxia
– Hypothermia
– Hypoglycemia
– Hypohydration
Additionally
• Suppressed Immune System
• Suppressed Emotional State
Stress of Altitude (Hypoxia)
• O2 % at sea level = 21%
O2 % at 22,000 ft = 21%
So why do we not assimilate as much O2 at
altitude as at sea level?
• Decreased PO2 results in Hypoxia.
– What is PO2?
– How does O2 diffuse into blood and tissues?
– How does PO2 effect this?
Acclimatization
(adaptation to the new natural environment)
IMMEDIATE
• Respiratory
– Hyperventilation
– Body Fluids become more base as a result of
reduction in CO2 w/hyperventilation
• Cardiac
– Increased heart rate at rest and at submax work =
increased cardiac output
– Stroke Volume remains the same or decreases
– Max VO-2 remains the same
Acclimatization
LONGER TERM (day to weeks)
• Respiratory
– Hyperventilation
– Excretion of base via kidneys and concomitant
reduction in alkaline reserve
• Cardiac
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Increased Sub-max Heart Rate
Sub-max cardiac output falls
Stroke volume decreases (Startlings Law)
Max VO-2 Decreases (decreased max HR and
stroke volume)
Acclimatization
• Hematological
– Decreased plasma volume
– Increased hematocrit (?)
– Increased hemoglobin
– Increased # of RBCs
– Possible increase in capillary beds (?)
– Increased 2,3 DPG
– Increased mitochondrial density
– Increased aerobic enzymes in muscle
Acclimatization
• Catecholamine Response
– Nor-epinephrine
• Regulates HR, BP, SV, Vasc Resistance and
substrate use.
• Increases for 7 days and then stabilizes.
– Epinephrine shows little to no increase
Acclimatization
(Acid Base Balance)
• Hyperventilation leads to a decrease in
carbon-dioxide thus increasing pH of all
body fluids. This blunts respiratory control.
• Body begins to excrete base through renal
tubules to normalize pH
• This increases resp. sensitivity and allows
for greater hyperventilation.
Acclimatization
(Acid Base Balance)
• This decrease in “base” creates a loss of
the absolute alkaline reserve inhibiting the
bodies acid buffering ability.
• This is made up for by a decrease in acid
production as a result of reduced CNS
drive, a decrease in intracellular ADP and
a reduction in epinephrine output.
Acclimatization Schedule
• Rapid ascent 0 to 7,500 ft 2 weeks to adjust.
• then 1 week per 2,000 ft up to 15,000 ft.
Riiiiight!
Climb to camp altitude
Active acclimatization
Move to next camp
Repeat as necessary
Summit
Get off the top!
Altitude Related Illnesses
• All are exacerbated by:
– Speed of ascent
– Altitude
– Health of Individual
– General susceptibility of individual
Altitude Related Illnesses
• Slow Ascent Symptoms
– Diminished exercise capacity
– Shortness of breath
– Elevated HR
– Cheyne-Stokes (irregular nighttime breathing)
Altitude Related Illnesses
Rapid Ascent
• Acute Mountain Sickness (AMS)
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Most common alt disorder
Can appear within 2 hours of ascent
Headache
Insomnia
Irritability
Weakness
Vomiting
Tachycardia
Breathing problems
Altitude Related Illnesses
Rapid Ascent
• High Altitude Pulmonary Edema (HAPE)
– 12 to 96 hours of ascent
– Can be treated on site but reduction in
elevation is best
Altitude Related Illnesses
Rapid Ascent
• High Altitude Cerebral Edema (HACE)
• Results from vasodilatation, increased
capillary hydrostatic pressure.
• Must descend to accurately diagnose and
treat.
Altitude Related Illnesses
Rapid Ascent
• Chronic Mountain Sickness (CMS)
– Can occur after months or years at altitude.
• Polycythemia
• Genetically linked EPO response to stress.
Altitude Related Illnesses
Rapid Ascent
• High Altitude Retinal Hemorrhage (HARH)
– All climbers experience over 21,000 ft
– Hemorrhage of the macula results in vision
loss.
NOTE – Eye Surgery
Body Composition and Nutrition
Muscle Atrophy and weight loss occur at altitude.
Depressed appetite
Dehydration
Increase BMR
Increased energy output
EAT, DRINK AND BE MERRY.
Body Composition and Nutrition
• Hypohydration
– Increased respirations – dehydration
– Low Relative Humidity at altitude
– Greater loss in fecal matter
– Less absorption in gut
– Inadequate fluid intake
• Low desire
• Difficult to obtain
Physical Performance at
Altitude
• Max strength is unaffected
• Capacity for repeated contractions is
progressively impaired
• Endurance is initially decreased but
improves with acclimatization.
• Decrease motor skills
– What track and field records broken at
altitude?
Mental Performance at Altitude
• Blood flow to the brain is not compromised
• Decreased short term memory
• Where did I park my car?
• Mental Acuity
• Let’s see it’s “I” before “E” except after no wait
it’s…
• Judgment/Decision making
• What are you thinking?
Summary
• As we gain alt the PO2 drops resulting in
inadequate hemoglobin saturation and a
decrease in aerobic capabilities
• Ability to perform high intensity short
duration (sprint) physical activity is not
affected.
• Why not?
• Reduced PO2 results in physiologic
responses that improve altitude tolerance.
Summary
• Hyperventilation and increased submax
cardiac output via elevated HR are the
primary immediate responses to altitude.
• Medical problems may emerge as a result
of travel to altitude.
• AMS, HAPE and HACE are the most
common conditions.
Summary
• Acclimatization entails
– Reestablishment of acid-base balance
– Increased synthesis of RBC and hemoglobin
– Improved local circulation and cellular
metabolism
Summary
• Rate of acclimatization depends on the
elevation. Major adjustments takes about 2
weeks but may require 4 to 6 weeks at higher
altitudes.
• Acclimatization does not fully compensate for
the stress of altitude as a result VO2max
remains depressed.
• Training at altitude provides no more benefit to
sea-level performance than equivalent sea level
training.