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Exercise Physiology > CH. 13 - Exercise at Altitude > Flashcards

CH. 13 - Exercise at Altitude Flashcards

1
Q

Pb (at sea level)

A

Barometric pressure = 760mmHg at sea level

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2
Q

PO2

A

partial pressure of oxygen

  • > reduced PO2 at altitude, limits exercise performance
  • > portion of Pb exerted by oxygen (about 21% x Pb = 159mmhg)
  • > PO2 at altitude = 132
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3
Q

hypobaria

A
  • > reduced Pb seen at altitude
  • > results in hypoxia (low PO2 in air), hypoxemia (low PO2 in blood)
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4
Q

effects of different altitudes on performance

A

Sea level = < 500m; no effects

Low altitude (500-2000m)

  • > no effects on well-being, performance may decrease but can be restored with acclimation

Moderate altitude (2000-3000m)

  • > performance and aerobic capacity decreases (on unacclimated ppl)
  • > performance may or may not be restored with acclimation

High altitude (3000-5500m)

  • > acute mountain sickness
  • > performance may or may not be restored with acclimation

Extreme high altitudes (>5500m)

  • > severe hypoxic effects
  • > highest settlements: 5200-5800m
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5
Q

altitude (in this course)

A

1500m

(this is considered a low altitude)

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6
Q

sea level Pb vs Mt Everest

A

SL Pb = 760mmHg

MT E Pb = 250mmHg

there is not less O2 on Everest, Pb is different

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7
Q

Pb vs Air composition at various altitudes

A

Pb varies, air composition does not

  • > PO2 is always 21% of Pb
  • > air PO@ affects PO2 in lungs, blood, tissues
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8
Q

air temp at altitude

A

temp decreases 1C per 150m ascent

  • > contributes to risk of cold-related disorders
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9
Q

Humidity at altitude

A
  • > cold air holds very little water
  • > air at altitude is very cold and very dry

dry air = quick dehydration via skin and lungs

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10
Q

how do general conditions vary at altitude

A
  • > solar radiation increases at high alts
  • > UV rays travel through less atmosphere
  • > water normally absorbs suns radiation, but low water vapour at altitude cannot
  • > snow reflects/amplifies solar radiation
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11
Q

pulmonary ventilation at altitude

A
  • > it will increase immediately at rest and submax exercise (but not maximal exercise
  • > decrease in PO2 stimulates chemoreceptors in aortic arch, carotids
  • > increases tidal volume for several hours/days

increase ventilation at altitude = hyperventilation

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12
Q

respiratory alkalosis

A

high blood pH

  • > caused by a decrease in alveolar PCO2 that increases CO2 gradient into the blood “blowing off CO2)
  • > oxyhemoglobin will. curve to the left
  • > prevents further hypoxia-driven hyperventialtion
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13
Q

why do kidneys excrete more bicarbonate at high altitudes

A

to offset pulmonary alkalosis

  • > bicarbonate ions buffer carbonic acid from CO2, thus reducing bloods buffering capacity will keep more acids in the blood, bringing pH back down
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14
Q

pulmonary diffusion

A

at rest, does not limit gas exchange with blood

at altitude, alveolar PO2 still = capillary PO2

  • > hypoxemia is a direct reflection of low alveolar PO2
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15
Q

gas exchange at muscles at altitude

A

PO2 gradient at muscle decreases

sea level: 100-40 = 60mmHg

4300m = 42-27 = 15mmHg

  • > O2 diffusion into the muscles is significantly reduced
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16
Q

why is the location of the oxygen gradient change critical?

A

hemoglobin desaturation at the lungs = no/little effect on performance

  • > decrease PO2 gradient at muscle = decrease exercise capacity
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17
Q

short term effects of acute altitude exposue

A

plasma volume will decrease within a few hours

  • > respiratory water loss, increase urine production
  • > lose up to 25% of plasma volume
  • > short term increase in hematocrit, O2 density
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18
Q

how are RBC affected by acute altitude exposure

A

RBC count increase after weeks/months

  • > hypoxemia triggers EPO (erythropoietin; hormone that increases RBC) release from kidneys
  • > increase RBC cell production in bone marrow
  • > long term increase in hematocrit
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19
Q

how is Cardiac output affected by acute altitude exposure

A

increases (despite decrease in plasma volume)

  • > at rest and sub max exercise (not max)
  • > delivers more O2 to tissues per minute
  • > increase SNS activity = increase HR
  • > inefficient, short term adaptation (6-10days)
  • after a few days muscles extract more O2*, decreased hypoxia
20
Q

how are basal metabolic rates impacted…

A

basal metabolic rates increase with…

  • > increase thyroxine and catecholamine secretions
  • > must increase food intake to maintain body mass
  • > more reliant on glucose vs fat
21
Q

how is anaerobic metabolism affected by altitude

A

it increases, resulting in increased lactic acid

  • > LA production will decrease over time
  • > there is no explanation for this
22
Q

why does appetite decline at altitude

A
  • > paired with increase metabolism = 500kcal/day deficit
  • > maintain iron intake to support increase in hematocrit
23
Q

why does dehydration occur faster at altitude

A
  • > increase water loss through skin, kidneys and urine
  • > exacerbated by sweating/exercise
  • > must consume 3-5L fluid/day
24
Q

VO2max at altitude

A

decreases at altitude above 1500

  • > due to decrease in arterial PO2 and Qmax
  • > drops 8-11% per 1000m ascent
25
Q

relate VO2 max change at different levels above sea level

A

given tasks still have the same absolute O2 requirement

Higher sea level VO2max - easier perceived effort

lower sea level VO2 max - harder perceived effort

26
Q

anaerobic performance at altitude

A

UNAFFECTED

ex. 100-400m sprints
- > minimal O2 requirements

27
Q

thinner air =

A

less air resistance

  • > improve swim run and jumos
28
Q

acclimation

A

chronic exposure to altitude

  • > affords improved performance but performance may never match that at sea level
  • > pulmonary cardiovascular and skeletal muscle changes
29
Q

how long dos it take for acclimation to occur

A

takes three weeks at moderate altitude

  • > add 1 week/every 600m
  • > lost within 1 month at sea level
30
Q

pulmonary adaptations of acclimation

A
  • > increase ventilation at rest during submaximal exercise
  • > resting ventilation rate 40% higher than at sea level
  • > submaximal rate is 50% higher
31
Q

blood adaptations to acclimation

A
  • > EPO release increase 2-3 days
  • > stimulates polycythemia (inc. RB count and hematocrit)
  • > elevated RBC for 3+ months
32
Q

consequences of polycythemia

A

hematocrit at sea level = 45%

hematocrit at 4500m = 6%

  • > hemoglobin increase proportional to elevation
  • > oxyhemoglobin curve may or may not shift
33
Q

how does plasma volume change with acclimation

A

plasma volume decreases then increases

early loss: hematocrit prior to polycythemia

later increase - increase SV and Q

34
Q

muscular adaptions to acclimation

A

Function and structure design

  • > cross-sectional area increases
  • > capillary density increases
  • > decrease muscle mass due to weigh loss, possible protein wasting

Metabolic demand (decreases)

  • > mitochondial function and glycolytic enzymes decrease
  • > oxidative capacity decreases
35
Q

altitude acclimation effects training and performance

A
  • > hypoxia at altitude prevents high intensity aerobic training
  • > living and training high leads to dehydration, low BV, low muscle mass
  • > value of altitude for training for sea level performance not validated
36
Q

two strategies for sea level athletes who must compete at altitude

A

1 compete ASAP after arriving at alt

2 train high for 2 weeks before competing

37
Q

why is live high, train low the best of both worlds

A
  • > permits passive acclimation to altitude
  • > trainin intensity not compromised by low PO2
38
Q

artificial altitude training

A

attempt to gain benefits of hypoxia at sea level

  • > breath hypoxic air 1-2 hrs per day and train normally
  • > didn’t show improvments
39
Q

train high vs train low

A

train high stimulates altitude acclimation

train low does not lose altitude acclimation

training low permits maximal aerobic training

live high train low is not scientifically validated yet

40
Q

acute altitude (mountain) sickness

A
  • > 6-48hrs after arrival
  • > headache, nausea, dyspnea
  • > can develop into more lethal conditions
41
Q

variability of altitude sickness

A

varies significantly

  • > increase with altitude, rate of ascent, susceptibility
  • > frequency = 7-22% of ppl at 2500-3500m
  • > women have higher incidence than men
42
Q

possible causes of altitude sickness

A
  • > low ventilatory response to altitude
  • > CO2 accumulates, acidosis
43
Q

most common symptom of altitude sickenss

A

headache

  • > most experienced >3600m
  • > continuous and throbbing
  • > worse in morning and after exercise
  • > hypoxia = cerebral VD - stretch pain receptors
  • > can also cause insomnia
44
Q

altitude sickness treatment and prevention

A
  • > gradual ascent to alt
  • > acetazolamide
  • > artificial oxygen, hyperbaric rescue bag
45
Q

2 life thratening conditions of altitude

A

high altitude pulmonary edema (HAPE)

high altitude cerebral edema (HACE)

46
Q

HAOE causes, symptoms, and treatment

A

causes

  • > likely related to hypoxic pulmonary VC

symptom

  • > shortness of breath, cough, tightness, fatigue

treatment

  • > suplemental O2
47
Q

HACE causes, symptoms, and treatment

A

Causes

  • > complication of HAPE > 4300m, endemic pressure buildup in inter cranial space

symptoms

  • > confusion, lethargy, ataxia

treatment

  • > supplemental O2, hyperbaric bag
  • > immediate descent to lower altitude

Exercise Physiology (19 decks)

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