1. Exercise and Altitude
Chapter 23 Brooks
Ch 24 McArdle, Katch and Katch

2. Outline Introduction to Altitude Acute altitude exposure
Acclimatization
Pulmonary Function
Cardiovascular Function
Muscle
Nutrition
Metabolism
Athletics at Altitude
Training
Ergogenic aids

4. Exercise and Altitude Moderate altitude >1524m (5000ft)
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)

6. Exercise and Altitude Extreme altitude > 6000m(20000ft)
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

8. 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%)

9. 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
Increased resting and sub-maximal heart rate and ventilation
Increased catecholamine secretion
Decreased VO2 max
Few acute changes in blood, muscle or liver

12. Human Responses
With proper acclimatization humans can tolerate high altitudes
Table ability to adapt
HIF-1 (hypoxia inducible factor 1) transcription factor that is augmented in hypoxic conditions NOS, Cox-2,
Synthesis of EPO, glycolytic enzymes, angiogenesis

14. 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

15. 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

16. Pulmonary Function HVR - Hypoxic Ventilatory Response
fig ventilation during exercise
Important to maintain Alv and Art O2
Which determines Max O2 utilization
Elite athletes - often have blunted HVR

17. Pulmonary Function
Fig O2 tensions at rest and exercise

20. Pulmonary Function
Fig O2 tensions at rest and exercise

21. 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

22. 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

24. Brooks, Exercise Physiology 2005
3,000 m
5,500 m
Brooks, Exercise Physiology 2005

25. 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

27. 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

31. 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 reduce vasodilation

32. 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

33. Nutrition and Energetics
Weight loss and muscles atrophy are common average 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 acclimatization

34. 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

36. 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

39. Athletics at Altitude Decreased endurance performance
Table 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 (more work)

41. 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
Fig 21.6 (Brooks)
VO2 Max and Running Endurance improved
3000m performance improved (elite)
Only some subjects were ‘responders’- significant EPO production with altitude

43. Live High - Train Low
Either live at m 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

45. 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