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 does alveolar Po2 determine 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
How much does air temperature decrease with ascent?
- About 1C per 150m
What is the average temperature near the summit of Mount Everest?
-40C
What poses a serious risk of cold-related disorders at altitude?
- Low temperature
- Low ambient water vapor pressure
- High winds
How does the extremely low partial pressure of water at high altitude lead to dehydration?
- Evaporation of moisture from skin surface due to the large gradient between skin and air
At what point would there be a significant change in hemoglobin percent saturation with O2?
- approx 3000m
What happens to hemoglobin oxygenation when you transition from moderate to higher altitudes?
- Dramatic decrease
- Negative affect 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 is the response to immediate exposure of elevations >2300m?
- Rapid physiologic adjustments to compensate for thinner air and the accompanying reduction in alveolar PO2
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 hyperventilation from reduced arterial Po2 reflect?
- Significant immediate response to native low-landers to altitude exposure
What does a hyperventilation response to high altitudes do?
- Hypoxic drive increases
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
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?
- Remains unchanged
What compensates for arterial desaturation at altitude?
- Increased submaximal exercise blood flow
What happens to the sympathoadrenal activity during rest and exercise with altitude?
- Progressively increases over time
What coincides with increased blood pressure and heart rate at altitude?
A steady rise in:
- Plasma levels
- 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 Catecholamine Response of Altitude?
- Check Notes
Sketch the Comparison of O2 Cost and Relative Strenuousness of submaximal exercise at sea level and altitude
- Check Notes
Sketch the comparison of cardiorespiratory and metabolic responses during exercise at Sea Level and Altitude
- Check Notes
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
What leads to moderate dehydration and accompanying dryness of lips, mouth, and throat at high altitudes?
- Fluid loss
When does fluid loss become pronounced at high altitudes? Why?
When
- physically active people
Why
- large daily total sweat loss
- Exercise pulmonary ventilation
Sketch the response to altitude of sensory functions
- Check Notes
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 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 does the blood of a typical miner in the Andes contain?
- 38% more erythrocytes than lowlanders
What happens to well-acclimatized mountaineers’ blood carry?
- More oxygen per deciliter than lowland residents
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?
- Initiate remodeling of capillary diameter and length
How does chronic hypoxia’s initiation of remodeling of capillary diameter and length?
- formation of new capillaries
What does the formation of new capillaries due to chronic hypoxia do?
- Increase oxygen conductance to neural tissues
What do human residents of sea level also increase during an altitude stay?
- Increase tissue capillarization
What reduces the oxygen diffusion distance between blood and tissues? What does it do?
What
- Prolific Microcirculation
Do
- Optimizes tissue oxygenation at altitude when arterial PO2 decreases
What do muscle biopsy specimens from humans living at altitude indicate?
- 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
Sketch the Oxygen-Hemoglobin Dissociation Curve
- Check Notes
What does prolonged high-altitude exposure do to lean body mass and body fat?
- Reduction
What does daily caloric intake from depressed appetite decrease by during the exposure period?
- 43%
By how much did reduced energy intake reduce body mass? What is this predominantly from?
How much
- 7.4kg
from
- muscle component of fat-free body mass
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 with lower cardiac output at high altitudes?
- Submax oxygen consumption remains stable through expanded a-vO2diff
When does maximum cardiac output decrease? what happens after?
- after 1 week above 3048m
- Remains lower throughout stay
What is the reduced 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?
- 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
- Reduced Max Q
Why do increases in the blood’s oxygen-carrying capacity not necessarily increase sea-level performance?
- Reductions in Maximum Cardiac Output
