1. Chapter 13
Exercise at Altitude

2. CHAPTER 13 Overview Environmental conditions at altitude
Physiological responses to acute altitude exposure
Exercise and sport performance at altitude
Acclimation: chronic exposure to altitude
Altitude: optimizing training and performance
Health risks of acute exposure to altitude

3. Introduction to Exercise at Altitude
Barometric pressure (Pb) ~760 mmHg at sea level
Partial pressure of oxygen (PO2)
Portion of Pb exerted by oxygen
x Pb ~159 mmHg at sea level
Reduced PO2 at altitude limits exercise performance
Hypobaria
Reduced Pb seen at altitude
Results in hypoxia, hypoxemia

4. Environmental Conditions at Altitude
1644: Torricelli develops mercury barometer
1648: Pascal demonstrates reduced Pb at high altitudes
1777: Lavoisier describes O2 and other gases that contribute to Pb
1801: Dalton’s law of partial pressures
Late 1800s: effects of hypoxia on body recognized
(continued)

5. Environmental Conditions at Altitude (continued)
Sea level (<500 m): no effects
Low altitude (500-2,000 m)
No effects on well-being
Performance may be , restored by acclimation
Moderate altitude (2,000-3,000 m)
Effects on well-being in unacclimated people
Performance and aerobic capacity 
Performance may or may not be restored by acclimation
(continued)

6. Environmental Conditions at Altitude (continued)
High altitude (3,000-5,500 m)
Acute mountain sickness
Performance , not restored by acclimation
Extreme high altitude (>5,500 m)
Severe hypoxic effects
Highest settlements: 5,200 to 5,800 m
For our purposes, altitude = >1,500 m
Few (if any) physiological effects <1,500 m
(continued)

7. Environmental Conditions at Altitude (continued)
Pb at sea level exerted by a 24 mi tall air column
Sea level Pb: 760 mmHg
Mt. Everest Pb: 250 mmHg
Pb varies, air composition does not
20.93% O2, 0.03% CO2, 79.04% N2
PO2 always = 20.93% of Pb
159 mmHg at sea level, 52 mmHg on Mt. Everest
Air PO2 affects PO2 in lungs, blood, tissues
(continued)

8. Figure 13.1

9. Environmental Conditions at Altitude (continued)
Air temperature at altitude
Temperature decreases 1 °C per 150 m ascent
Contributes to risk of cold-related disorders
Humidity at altitude
Cold air holds very little water
Air at altitude very cold and very dry
Dry air  quick dehydration via skin and lungs
(continued)

10. Environmental Conditions at Altitude (continued)
Solar radiation  at high altitude
UV rays travel through less atmosphere
Water normally absorbs sun radiation, but low water vapor at altitude can’t
Snow reflects/amplifies solar radiation

11. Physiological Responses to Acute Altitude Exposure
Pulmonary ventilation  immediately
At rest and submaximal exercise (but not maximal exercise)
–  PO2 stimulates chemoreceptors in aortic arch, carotids
–  Tidal volume for several hours, days
•  Ventilation at altitude = hyperventilation
Alveolar PCO2    CO2 gradient, loss
Blowing off CO2 = respiratory alkalosis
(continued)

12. Physiological Responses to Acute Altitude Exposure (continued)
Respiratory alkalosis = high blood pH
Oxyhemoglobin curve shifts left
Prevents further hypoxia-driven hyperventilation
Kidneys excrete more bicarbonate
Minimizes blood buffering capacity
Reverses alkalosis, blood pH decreases to normal
(continued)

13. Physiological Responses to Acute Altitude Exposure (continued)
Pulmonary diffusion
At rest, does not limit gas exchange with blood
At altitude, alveolar PO2 still = capillary PO2
Hypoxemia a direct reflection of low alveolar PO2
Oxygen transport
–  Alveolar PO2   O2 hemoglobin saturation
Oxyhemoglobin dissociation curve shifts left
Shape and shift of curve minimize desaturation
(continued)

14. Figure 13.2

15. Animation 13.2
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16. Figure 13.3

17. Physiological Responses to Acute Altitude Exposure (continued)
Gas exchange at muscles 
PO2 gradient at muscle 
Sea level: 100 – 40 = 60 mmHg gradient
4,300 m altitude: 42 – 27 = 15 mmHg gradient
O2 diffusion into muscle significantly reduced
Location of gradient change critical
Hemoglobin desaturation at lungs  little/no effect
–  PO2 gradient at muscle   exercise capacity
(continued)

18. Physiological Responses to Acute Altitude Exposure (continued)
Short term: plasma volume  within few hours
Respiratory water loss,  urine production
Lose up to 25% plasma volume
Short-term  in hematocrit, O2 density
Red blood cell count  after weeks/months
Hypoxemia triggers EPO release from kidneys
–  Red blood cell production in bone marrow
Long-term  in hematocrit
(continued)

19. Physiological Responses to Acute Altitude Exposure (continued)
Cardiac output  (despite  plasma volume, stroke volume)
At rest and submaximal exercise (not maximal)
Delivers more O2 to tissues per minute
–  Sympathetic nervous system activity   HR
Inefficient, short-term adaptation (6-10 days)
After few days, muscles extract more O2
–  (a-v- )O2 difference
Reduces demand for cardiac output
(continued)

20. Physiological Responses to Acute Altitude Exposure (continued)
•  Q•max =  SVmax x  HRmax
•  SVmax due to  PV
•  HRmax due to  SNS responsiveness
•  PO2 gradient +  Q•max =  V•O2max
(continued)

21. Physiological Responses to Acute Altitude Exposure (continued)
Basal metabolic rate 
–  Thyroxine secretion
–  Catecholamine secretion
Must  food intake to maintain body mass
More reliance on glucose versus fat
•  Anaerobic metabolism   lactic acid
Lactic acid production  over time
No explanation for lactate paradox
(continued)

22. Table 13.1

23. Physiological Responses to Acute Altitude Exposure (continued)
Dehydration occurs faster
Water loss through skin, kidneys/urine
Exacerbated by sweating with exercise
Must consume ~3 to 5 L fluid/day
Appetite declines at altitude
Paired with  metabolism  500 kcal/day deficit
Athletes/climbers must be educated about eating at altitude
Maintain iron intake to support  in hematocrit

24. Exercise and Sport Performance at Altitude
V•O2max  as altitude  past 1,500 m
Atmospheric PO2 <131 mmHg
Due to  arterial PO2 and Q•max
Drops 8 to 11% per 1,000 m ascent
Mt. Everest ascent study, 1981
V•O2max  from 62 to 15 ml/kg/min
If sea level V•O2max <50 ml/kg/min, could not climb without supplemental oxygen
(continued)

25. Figure 13.4

26. Figure 13.5

27. Exercise and Sport Performance at Altitude (continued)
Aerobic exercise performance affected most by hypoxic conditions at altitude
V•O2max  as a percentage of sea level V•O2max
Given task still has same absolute O2 requirement
Higher sea-level V•O2max  easier perceived effort
Lower sea-level V•O2max  harder perceived effort
(continued)

28. Exercise and Sport Performance at Altitude (continued)
Anaerobic performance unaffected
For example, 100 to 400 m track sprints
ATP-PCr and anaerobic glycolytic metabolism
Minimal O2 requirements
Thinner air  less air resistance
Improved swim and run times (up to 800 m)
Improved jump distances
Throwing events, varied effects

29. Acclimation: Chronic Exposure to Altitude
Acclimation affords improved performance, but performance may never match that at sea level
Pulmonary, cardiovascular, skeletal muscle changes
Takes 3 weeks at moderate altitude
Add 1 week for every additional 600 m
Lost within 1 month at sea level
(continued)

30. Figure 13.6

31. Acclimation: Chronic Exposure to Altitude (continued)
Pulmonary adaptations
–  Ventilation at rest and during submaximal exercise
Resting ventilation rate 40% higher than at sea level (over 3-4 days)
Submaximal rate 50% higher (longer time frame)
Blood adaptations
EPO release  for 2 to 3 days
Stimulates polycythemia ( red blood cell count, hematocrit)
Elevated red blood cell count for 3+ months
(continued)

32. Acclimation: Chronic Exposure to Altitude (continued)
Consequences of polycythemia
Hematocrit at sea level: ~45%
Hematocrit at 4,500 m: ~60%
Hemoglobin  proportional to elevation
Oxyhemoglobin curve may or may not shift
Plasma volume , then 
Early loss   hematocrit prior to polycythemia
Later increase   stroke volume, cardiac output
(continued)

33. Figure 13.7

34. Acclimation: Chronic Exposure to Altitude (continued)
Muscle function and structure changes
Cross-sectional area 
Capillary density 
–  Muscle mass due to weight loss, possibly protein wasting
Muscle metabolic potential 
Mitochondrial function and glycolytic enzymes 
Oxidative capacity 
(continued)

35. Acclimation: Chronic Exposure to Altitude (continued)
Study of runners showed no major cardiovascular adaptations
2 months at altitude = more tolerant of hypoxia
But no changes in aerobic capacity
Possible cause: reduced atmospheric PO2 inhibited training intensity at high altitude

36. Altitude: Optimizing Training and Performance
Altitude acclimation confers certain advantageous adaptations for competing
Training possibilities for competition
Train high, compete low?
Train high, compete high?
Train low, compete high?
Live high, train low, compete high?
(continued)

37. Altitude: Optimizing Training and Performance (continued)
Hypoxia at altitude prevents high-intensity aerobic training
Living and training high leads to dehydra-tion, low blood volume, low muscle mass
Value of altitude training for sea-level performance not validated
Value of live high, train low?
(continued)

38. Altitude: Optimizing Training and Performance (continued)
Two strategies for sea-level athletes who must sometimes compete at altitude
1. Compete ASAP after arriving at altitude
Does not confer benefits of acclimation
Too soon for adverse effects of altitude
2. Train high for 2 weeks before competing
Worst adverse effects of altitude over
Aerobic training at altitude not as effective
(continued)

39. Altitude: Optimizing Training and Performance (continued)
Live high, train low: best of both worlds
Permits passive acclimation to altitude
Training intensity not compromised by low PO2
Outcome tested on 5 k run time trial
Live high, train high: no improvement
Live low, train low: no improvement
Live high, train low: significant improvement
(continued)

40. Altitude: Optimizing Training and Performance (continued)
Live high, train low more recently validated
Lived at 2,500 m, trained at 1,250 m
Pre- and posttesting at sea level
Aerobic performance improved 1.1%
V•O2max improved 3.2%
Additional evidence
48 athletes randomly assigned to 1 of 4 groups of athletes living at different altitudes (1780 m, 2085 m, 2454 m, 2800 m)
All trained together between 1250 and 3000 m
3 k time trial performance significantly improved for only those living in the middle two altitudes
(continued)

41. Figure 13.8

42. Video 13.1
When you are in the normal view of the PowerPoint slides, you should right-click on the image and then choose “Open hyperlink” to play the video. In the slide show view, you will simply click on the image to play the video. You must have an Internet connection in order to link to the streaming video.
In this video, Ben Levine explains the physiology behind the live high–train low approach.

43. Figure 13.9a

44. Figure 13.9b

45. Altitude: Optimizing Training and Performance (continued)
Artificial altitude training
Attempt to gain benefits of hypoxia at sea level
Breathe hypoxic air 1 to 2 h per day, train normally
No improvements
Alternating train high, train low
Training high stimulates altitude acclimation
Training low doesn’t lose altitude acclimation
Training low permits maximal aerobic training
(continued)

46. Altitude: Optimizing Training and Performance (continued)
Live high, train low at sea level
Sleep and live in hypoxic apartment ( PN2,  PO2)
Train normally
Not scientifically validated yet
Natural live high, train low best approach
Best for elite athletes
Nonelite exercisers may benefit from artificial approaches

47. Health Risks of Acute Exposure to Altitude
Acute altitude (mountain) sickness
Onset 6 to 48 h after arrival, most severe days 2 to 3
Headache, nausea/vomiting, dyspnea, insomnia
Can develop into more lethal conditions
Incidence of altitude sickness varies widely
 With altitude, rate of ascent, susceptibility
Frequency: 7 to 22% at 2,500 to 3,500 m
Women have higher incidence than men
(continued)

48. Figure 13.10

49. Health Risks of Acute Exposure to Altitude (continued)
Possible causes of altitude sickness
Low ventilatory response to altitude
CO2 accumulates, acidosis
Headache most common symptom
Mostly experienced >3,600 m
Continuous and throbbing
Worse in morning and after exercise
Hypoxia  cerebral vasodilation  stretch pain receptors
(continued)

50. Health Risks of Acute Exposure to Altitude (continued)
Altitude sickness insomnia
Interruption of sleep stages
Cheyne-Stokes breathing prevents sleep
Incidence of irregular breathing  with altitude
Altitude sickness prevention and treatment
Gradual ascent to altitude
Acetazolamine (+ steroids)
Artificial oxygen, hyperbaric rescue bags
(continued)

51. Health Risks of Acute Exposure to Altitude (continued)
Altitude  two life-threatening conditions
Both involve edema formation
High-altitude pulmonary edema (HAPE)
High-altitude cerebral edema (HACE)
Can develop from severe altitude sickness
Must be treated immediately
(continued)

52. Health Risks of Acute Exposure to Altitude (continued)
HAPE causes
Likely related to hypoxic pulmonary vasoconstriction
Clot formation in pulmonary circulation
HAPE symptoms
Shortness of breath, cough, tightness, fatigue
–  Blood O2, cyanosis, confusion, unconsciousness
HAPE treatment
Supplemental oxygen
Immediate descent to lower altitude
(continued)

53. Health Risks of Acute Exposure to Altitude (continued)
HACE causes
Complication of HAPE, >4,300 m
Edemic pressure buildup in intracranial space
HACE symptoms
Confusion, lethargy, ataxia
Unconsciousness, death
HACE treatment
Supplemental oxygen, hyperbaric bag
Immediate descent to lower altitude