Exercise and Altitude
Chapter 23 Brooks
Ch 24 McArdle, Katch and Katch
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Outline
• Introduction to Altitude
• Acute altitude exposure
• Acclimatization
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Pulmonary Function
Cardiovascular Function
Muscle
Nutrition
Metabolism
• Athletics at Altitude
– Training
– Ergogenic aids
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Exercise and Altitude
• Research conducted in many places
– expeditions to Mt Everest (8850m)(235 mmHg)
– simulations in barometric chambers
• Various altitudes and pressures
– at Pikes Peak research center in Colorado (4300m)(450mmHg)
– as well, research with altitude populations in the Andes (Quechuas)
and Himalayas (Sherpas) has provided interesting data
• Moderate altitude >1524m (5000ft)
– Decreases in maximum O2 consumption begin in most
people
• Elite athletes may experience declines in VO2 max as low a 580 m
(1900ft)
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Exercise and Altitude
• Fig 23-3,4 effect of altitude on VO2max
– 3% decline / 300m (1000ft)
– O2 cost of work is similar - perception of effort is greater higher % of max
• Extreme altitude > 6000m(20000ft)
– Progressive deterioration towards death
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Acute Altitude Exposure
• Sea Level 760mmHg(PIO2 159mmHg)
• Fig 23-2 less O2 available
– As barometric pressure decreases
• Less air in given volume
– Less O2 per volume of air
• same % O2 as sea level (~ 21%)
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Acute Altitude Exposure
• Hypoxia - low levels of oxygen
– Oxygen transport capacity decreases with increasing altitude, even
with compensations outlined below
• Table 23-1 Effects of Acute exposure
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Increased resting and sub-maximal heart rate and ventilation
Increased catecholamine secretion
Decreased VO2 max
Few acute changes in blood, muscle or liver
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Human Responses
• With proper acclimatization humans can tolerate high
altitudes
– Table 23-2 - ability to adapt
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Human Responses
• Slow ascent to 5500m (18000ft) can be
accomplished with few symptoms
– Recommend 2 weeks to adjust to altitudes up to 2300m
– Additional week for each 610 m up to 4600m
• If ascent is rapid -AMS -acute mountain sickness - can occur
within a few hours
– Headache, nausea, irritability, weakness, poor appetite,
vomiting, tachycardia, disturbed breathing
• Above 3000m AMS is common
– Those with a blunted breathing response are more
susceptible
– Slow ascent can reduce risk of AMS
– Acclimatization hikes are important
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Pulmonary Function
• Ventilation increases further for first 2 weeks of
exposure to a given high altitude
– Hypoxia is the driving force
– Bicarbonate is excreted by kidneys - increasing
central and peripheral sensitivity for ventilation
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Pulmonary Function
• HVR - Hypoxic
Ventilatory Response
– fig 23-5 - ventilation
during exercise
– Important to maintain
Alv and Art O2
– Which determines
Max O2 utilization
– Elite athletes - often
have blunted HVR
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Pulmonary Function
• Fig 23-6 - O2 tensions at rest and exercise
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Pulmonary Function
• Fig 23-6 - O2 tensions at rest and exercise
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Pulmonary Function
• Observe decrease in PaO2 with intense exercise
– May be pulmonary gas exchange causing diffusion limitation at
altitude
– Partial Pressure of O2 determines driving force
– Fig 23-7b - same transit time - dec driving force (slope) at altitude
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pH Changes and Ventilation
• Higher ventilation decreases PCO2
– Blood becomes more alkaline
• First Week
• Decrease bicarbonate level in cerebrospinal fluid
resulting from active transport and kidney excretion
– helps to normalize pH
– improves respiratory control at altitude
– influence of bicarbonate release on pH is limited - at high
altitude blood still alkaline
• Fig 23-7 a - O2 Hb dissociation curve
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3,000 m
5,500 m
Brooks, Exercise Physiology 2005
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pH Changes and Ventilation
• Higher ventilation inc PaO2 but also cause shift of curve to
left
– tighter bond between Hb and O2
– require lower PO2 to release O2 at tissues
• Bicarb excretion shifts curve back to right
– Helps unloading of O2 at tissues
• increased content of 2,3-DPG in rbc’s causes curve to shift
further to the right
– Advantageous only to 5000m - then impairs ability to pick up O2 at
the lungs
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Cardiovascular Adjustments
• Acute submaximal exercise
– HR inc; SV ~ same; Q inc; VO2 inc
• Acclimatized submaximal exercise
– HR still high; SV dec,
– Q dec 20-25% (after 1-2 weeks);
– VO2 ~same
• MAP - Mean Arterial BP - gradually increases with exposure
– Due to inc systemic resistance and vascular resistance in muscle
– inc blood viscosity and catecholamines
• Above 3000m EPO stimulates Hb and Hct - requires several
weeks
– Time reduced with adequate energy, protein and iron intake
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Acclimatization
• Rate Pressure Product - work load on heart (HR *
Systolic BP)
– Shown to inc 100% in some individuals with exercise at
3000m and above
– Poses significant challenge to the heart
• Lungs -PAP-pulmonary Arterial P
– Inc with altitude due to
• sympathetic stimulation
• Inc size of sm ms in pulmonary arterioles
– Implicated in HAPE (high altitude pulmonary edema)
• Brain - hypoxemia - vasodilation
– Implicated in HACE (cerebral edema)
– Hypocapnea causes vasoconstriction in brain which can
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reduce vasodilation
Muscle Acclimatization
• During exercise
– Sub-maximal blood flow decreases by about 20-25%
– Due to inc Nor Epinephrine and decreased Q
– O2 delivery maintained - through increased O2 content in
blood
• Inc myoglobin, buffering capacity, aerobic enzymes
CS (small change)
– Enhances tissue oxygenation and acid base balance
• Oxidative capacity - no change??
– Altitude native populations - low mitochondrial volume
• Activity limited by pulmonary ventilation and arterial O2 content
– Even unfit are thought to have sufficient muscle
Oxidative capacity at altitude
– Endurance capacity increases with acclimatization
– with no change in VO2 max
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Nutrition and Energetics
• Weight loss and muscles atrophy are common average 100200 g/day – dehydration, energy deficit, increased activity and BMR
– High carbohydrate diet
recommended > 60%
• Exercise Energetics
• Lactate paradox - fig 23-9
– Blood lactate is higher at given power output with acute
exposure compared to sea level and acclimatization
– Paradox is that there is no change in VO2 max with 33
acclimatization
Nutrition and Energetics
• Fig 23-10
– research suggests that acclimatization results in Dec Ep, (Nor Ep
stays high)
• Reduced glycogen mobilization
– Working ms oxidizes more of its own lactate - inc dependence on bld
glucose
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Fuel Metabolism
• Carbohydrates - thought to be preferred fuel - higher
yield of ATP/O2
• CHO has very limited storage
– Hypoglycemia and liver glycogen depletion common at
altitude
– Reduced with high carbohydrate diet
• Fat and Protein
– Increased fat catabolism at altitude if diet is inadequate
– Gluconeogenesis - loss of muscle mass also occurs with
low CHO intake
• Working muscle shown to prefer CHO at altitude
– Use of protein for gluconeogenesis has detrimental
impact on long term exercise/work potential
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Athletics at Altitude
• Table 23-3 -Mexico City Olympics (1968)
– ~ 2240m (7350ft)
• Improvements in short duration, high intensity events
– Reduced gravity and wind resistance
• Decreased endurance performance
– longer than 800m
• Athletes benefit from 1-12 weeks of acclimatization
• Problem - reduced absolute training intensity at altitude-even
if same relative %
– Can not train as hard - detraining effect
– Further - do not see improvements in sea level
performance (reduction)
– Reduced bld volume, buffering capacity, inc ventilation
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(more work)
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Live High - Train Low
• Combine benefits of sedentary adaptations to
altitude with maximal training stimulus near sea
level
• Increased capacity to compete at moderate altitude
– Recent research has also illustrated an increased
capacity for exercise at sea level with live high-train low
• Levine, Stray-Gunderson and Chapman
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Fig 21.6 (Brooks)
VO2 Max and Running Endurance improved
3000m performance improved (elite)
Only some subjects were ‘responders’- significant EPO
production with altitude
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Live High - Train Low
• Either live at 2200-3500m and drive down every day to train
(<1200m)
– This altitude found to stimulate rbc production, but to not cause AMS
symptoms in athletes
• Or sleep in hypoxic tent with reduced oxygen tension
(14%O2 - PIO2 106mmHg)
– Stimulates adaptation while you sleep
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Ergogenic Aids and Altitude
• Significant use of EPO and synthetic analog of EPO at Salt
Lake City Olympics
• Several athletes stripped of their medals in cross country
skiing
• Used darbepoietin - novel erythropoiesis stimulating protein
• Developed for the treatment of of chronic anemia in patients
on renal dialysis
– Longer half life than EPO, needs to be taken less frequently, but also
stays in system longer making detection easier
• Currently, limits of absolute levels of Hb and/or Hct are in
place
– 50% and 17g/dl (males)(varies with organization)
• Proposals for indirect analysis of soluble transferrin
receptors and serum erythropoietin which can be done in
minutes
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