Chapter 24 - Physical Activity at Medium and High Altitude Flashcards
What are the effects of being at near sea-level altitude?
No Effects On:
- Well-being
- Performance
What is considered near sea-level altitude?
- Below 500m
What is considered low altitude?
- 500-2000m
What are the effects of low altitude/
- No effect on well-being
- Performance may be diminished
At what level of low altitude might athletes performance be diminished?
- above 1500m
How might performance decrements seen in low-altitude be overcome?
- Acclimatization
What level is moderate altitude?
- 2000m-3000m
What effects are seen at moderate altitudes?
- Well-being effects on unacclimated individuals
- Decreased maximal aerobic capacity and performance
Can optimal performance at moderate altitude be restored?
- may or may not be restored with acclimatization
What level is considered high altitude?
- 3000-5500m
What are the effects of high altitude?
- Adverse health effects in most individuals
- Significant performance decrements even with full acclimatization
What does the physiologic challenges at high altitude come from?
- decreased ambient partial pressure of oxygen (Po2)
What does the oxygen transport cascade refer to?
- Progressive changes in the environment’s O2 pressure and body areas
What does the oxygen transport cascade represent?
- Oxygen cascade at different elevations
What must air that we inspire be?
- Warmed and humidified
What is the partial pressure of water at body temperature?
- 47mmHg
What is alveolar Po2 determined by?
- The removal of O2 into the pulmonary capillary blood and the addition of O2 from ventilation
What is the slight decrease in Po2 between alveolar air and arterial blood?
- 5mmHg
What is the Po2 of 40mmHg in mixed-venous blood due to?
- Tissue oxygen use
What are some possible well-being effects at 1500m?
- Lightheadedness
- Headaches
What are some possible well-being effects at 3000m?
- Insomnia
- Nausea
- Vomitting
- Pulmonary Discomfort
What are some possible well-being effects at 4000m?
- Dyspnea
- Anorexia
- GI disturbances
What are some possible well-being effects at 6000m?
- Lethargy
- General Weakness
What are some possible well-being effects at 8000m?
- Impending collapse
At what altitude would there be a significant change in hemoglobin percent saturation with O2?
- approx 3048m
What happens to hemoglobin oxygenation when you transition from moderate to higher altitudes?
- Dramatic decrease
- Negative effect on mild-intensity aerobic exercise
Define Acclimatization
- Refers to adaptations produced by changes in the natural environment, whether through a change in season or place of residence.
Define Acclimation
- Adaptations produced in a controlled laboratory environment
What does altitude acclimatization describe?
- adaptive responses in physiology and metabolism that improve tolerance to altitude hypoxia
What are some important immediate adjustments made in response to elevations above 2300m?
Increase
- respiratory drive to produce hyperventilation
- Blood flow during rest and submaximal exercise
What does increased hypoxic drive in response to high altitudes do?
stimulate hyperventilation
When does an increase in hypoxic drive increase? How long does it remain elevated?
When
- First few weeks
How Long
- A year or longer during prolonged exposure
What happens to resting blood pressure in early stages of altitude adaptation?
- Increases
response
What happens to submaximal exercise heart rate and cardiac output in altitude?
- Rises to 50% above sea level values
What happens to stroke volume at submaximal exercise in altitude?
response not adaptation
- Remains unchanged
response to altitude
What compensates for arterial desaturation at altitude?
- Increased submaximal exercise blood flow
response to altitude
What happens to the sympathoadrenal activity during rest and exercise with altitude?
- Progressively increases over time
response
What coincides with increased blood pressure and heart rate at altitude?
what causes it?
A steady rise in:
- Plasma levels of epinephrine
- Excretion rates of epinephrine
What does an increased sympathoadrenal activity in altitude contribute to?
Regulation of:
- Blood pressure
- Vascular resistance
- Substrate mixture during short- and long-term hypobaric exposure
Sketch the Comparison of O2 Cost and Relative Strenuousness of submaximal exercise at sea level and altitude
- Check Notes
response
What allows body water to evaporate as inspired air becomes warmed and moistened in respiratory passages?
- Ambient air in mountainous regions remains cool and dry
response
What leads to moderate dehydration and accompanying dryness of lips, mouth, and throat at high altitudes?
- Fluid loss
response
When does fluid loss become pronounced at high altitudes? Why?
When
- physically active people
Why
- large daily total sweat loss
- Exercise pulmonary ventilation
How does altitude affect sensory functions
- altitude hinders sensory function
What are the immediate pulmonary acid-base responses to altitude?
- Hyperventilation
- Bodily Fluids become more alkaline due to reduction in carbon dioxide with hyperventilation
What are the longer-term pulmonary acid-base responses to altitude?
- Hyperventilation
- Excretion of base (HCO3-) via the kidneys and concomitant reduction in alkaline reserve
What are the immediate cardiovascular responses to altitude?
Increase
- submax HR
- submax Cardiac Output
Same or Slight Decrease
- Max Cardiac Output
- Stroke Volume
What are the longer-term cardiovascular responses to altitude?
- Submax HR elevated
- Submax Cardiac Output below sea-level
- Stroke Volume Decreases
- Max Cardiac Output decreases
What are the longer-term hematological responses to altitude?
Decreased
- Plasma Volume
Increased
- Hematocrit
- Hemoglobin Concentration
- Total # Red blood cells
What are the longer-term local responses to altitude?
Increased
- capillarization of skeletal muscle
- Red blood cell 2,3-DPG
- Mitochondria Density
- Aerobic Enzymes in Muscles
- Loss of body weight/lean body mass
how does the effect of hyperventilation at altitude to increase alveolar PO2 relate to the bodies CO2 level?
- Opposite Effect
What does carbon dioxide loss from fluids in the body create?
- Physiologic disequilibrium
How does the body manage the disequilibrium created by the carbon dioxide loss from fluids at altitude?
- Produces CO2 via the action of carbonic anhydrase
What does the high level of carbonic anhydrase activity do?
- decreases H+ in the blood
- Makes body fluids more alkaline
How does the body control ventilatory-induced alkalosis?
Very Slowly
- kidneys excrete base (HCO3-) through the renal tubules
What does the control of ventilatory-induced alkalosis by the kidneys through the renal tubules do?
Restores normal pH
What happens when the pH is restored by the kidneys following ventilatory-induced alkalosis?
- Increases the respiratory center’s responsiveness to enable an even greater hyperventilation response
What does establishing acid-base equilibrium with acclimatization occur at the expense of?
- Loss in absolute alkaline reserves
What happens to blood lactate concentrations during submaximal exercise on immediate ascent to altitude compared to sea-level values?
- Increased
What is an explanation for the increases in blood lactate accumulation during submax exercise during immediate ascent to altitude?
- Increased reliance on anaerobic metabolism
What happens to lactate following several weeks of altitude exposure at the same submaximal and maximal intensity exercises?
- Large muscle groups produce lower blood lactate levels
What does lower blood lactate levels at the same submax or max intensity following several weeks of altitude exposure occur despite of?
- Lack of increase in VO2max or regional blood flow in active tissues
Where does research point to involving the lactate paradox?
- Reduced output of epinephrine (during exercise)
- Its controversial
What does epinephrine do for glucose?
- Mobilizes hormone
What reduces the capacity for lactate formation?
- Reduced glucose mobilization
What might reduced lactate formation during maximal exercise at high altitudes partly reflect?
- Reduced CNS drive
What does a reduced CNS drive do?
- Reduces capacity for all-out effort
What is the most important longer-term adjustment to altitude exposure?
- Increase in blood’s oxygen-carrying capacity
What two factors account for the adaptation of increased blood oxygen-carrying capacity?
- Initial decrease in plasma volume
- Increase in erythrocytes and hemoglobin synthesis
What happens to the body fluid in the first several days of altitude exposure?
- Shifts from the intravascular space to the interstitial and intracellular space
What does the decrease in plasma volume that occurs within several hours of altitude exposure do?
- Increases red blood cell concentration
What happens after a week at 2300m regarding plasma volume?
- Declines about 8%
What happens after a week at 2300m regarding red blood cell concentration and hemoglobin?
Red Blood Cell Concentration
- Increases 4%
Hemoglobin
- Increases 10%
What does the rapid plasma volume reduction do compared to the arrival at altitude values?
- increases the oxygen content of arterial blood
Define Diuresis
- Increased urine output that accompanies the fluid shift from plasma during acclimatization
What does diuresis do?
- Maintains balance in the fluid compartments despite a lower total body water content
What does a reduced arterial Po2 at altitude stimulate?
- Increase in total number of red blood cells, or polycythemia
What initiates red blood cell formation?
- Erythropoietin
How quickly does the initiation of red blood cell formation from erythropoietin occur?
- within 15 hours after altitude ascent
Where does erythrocyte get produced?
- The marrow of the long bones
What happens to erythrocyte production during prolonged altitude stay?
- Remains elevated
What is seen in some healthy high-altitude natives?
- High red blood cell count compared to native lowlanders
What is the result of increased hemoglobin concentration?
- Even with reduced hemoglobin oxygen saturation at altitude, the quantity of oxygen in arterial blood may approach or even equal sea-level values
What can chronic hypoxia do to capillaries?
- Initiate remodeling of capillary diameter and length
- increase capillarization
What does the formation of new capillaries due to chronic hypoxia do?
- Increase oxygen conductance to neural tissues
What happens to myoglobin at altitude?
- Myoglobin increases up to 16% after acclimatization
What does additional myoglobin do?
- augments oxygen “storage” in specific fibers
- Facilitates intracellular oxygen release and delivery at a low-tissue PO2
What does the increased concentration of red blood cell 2,3-Diphosphoglycerate (2,3-DPG) facilitate?
- Oxygen release from hemoglobin in long-term altitude exposure
What does prolonged high-altitude exposure do to lean body mass and body fat?
- Reduction
What does time required for acclimatization depend on?
- Elevation
Does acclimatization to one altitude ensure acclimatization to higher elevations?
- Only partial adjustments
How long does it take to adapt to altitude up to 2300m?
- approx 2 weeks
What is the acclimatization rate after the initial 2 weeks for 2300m?
- 610m every week
When do small declines in VO2max become noticeable?
- 589m
What is the rate of decrease in VO2max due to arterial desaturation?
- 7-9% per 1000m
- Altitudes up to 6300m
When does the rate of VO2max decrease drastically?
- above 6300m
What does VO2max average at 7000m?
- one half that at sea level
Why might there be small improvements in endurance during acclimatization, despite lack of concomitant increases in VO2max?
- Increase in minute ventilation
- Increase arterial oxygen saturation/cellular aerobic functions
- Blunted blood lactate responses
What happens to VO2max after several months of acclimatization despite relatively rapid increases in hemoglobin concentration?
- Remains below sea-level values
What offsets the hematologic benefits of acclimatization?
- Lower max HR
- Decreased Stroke Volume
What increases submaximal cardiac output at altitude?
- immediate response to physical activity
What happens to increases in submax cardiac output as acclimatization progresses?
- Diminishes
- Does not improve with prolonged exposure
What happens to progressive decreases in stroke volume during altitude?
- Stays reduced
What happens to submaximal oxygen consumption at high altitudes?
- Submax oxygen consumption remains stable through expanded a-vO2diff
- compensates for decreased cardiac output
When does maximum cardiac output decrease in appreciable amounts? what happens after?
- after 1 week above 3048m
- Remains lower throughout stay
What is the reduced maximal blood flow in high altitude a combined effect of?
- Decreased plasma volume (reduced stroke volume)
- Increase in parasympathetic tone
What is the increase in parasympathetic tone at high altitude induced by? What does it do?
- prolonged altitude exposure
- reduces maximum heart rate
When doesnt sea-level exercise performance improve after living at altitude?
- When VO2max serves as improvement criterion
What effects of high altitude acclimatization do not enhance sea-level performance?
- Residual muscle mass loss
- Reduced max HR and SV
Why do increases in the blood’s oxygen-carrying capacity not necessarily increase sea-level performance?
- Reductions in Maximum Cardiac Output
