Exercise at AltitudeExercise at Altitude

Who performs better at a bike Who performs better at a bike race in San Francisco… the race in San Francisco… the

athlete who trains at altitude, or athlete who trains at altitude, or the athlete who trains sea level?the athlete who trains sea level?

Why?Why?

How high is high?How high is high?• Moderate = <12,000 ft

• High = 12,000 to 18,000 ft

• Very High = >20,000 ft

Stress of AltitudeStress of Altitude• The 4 “H”s

– Hypoxia– Hypothermia– Hypoglycemia– Hypohydration

Additionally• Suppressed Immune System• Suppressed Emotional State

Stress of Altitude (Hypoxia)Stress of Altitude (Hypoxia)• O2 % at sea level = 21%

O2 % at 22,000 ft = 21%

So why do we not assimilate as much O2 at altitude as at sea level?

• Decreased PO2 results in Hypoxia.– What is PO2?

– How does O2 diffuse into blood and tissues?

– How does PO2 effect this?

Acclimatization Acclimatization (adaptation to the new natural environment)(adaptation to the new natural environment)

IMMEDIATE• Respiratory

– Hyperventilation– Body Fluids become more base as a result of reduction

in CO2 w/hyperventilation

• Cardiac– Increased heart rate at rest and at submax work =

increased cardiac output– Stroke Volume remains the same or decreases– Max VO-2 remains the same

AcclimatizationAcclimatizationLONGER TERM (day to weeks)

• Respiratory– Hyperventilation– Excretion of base via kidneys and concomitant

reduction in alkaline reserve

• Cardiac– Increased Sub-max Heart Rate– Sub-max cardiac output falls– Stroke volume decreases (Startlings Law)

– Max VO-2 Decreases (decreased max HR and stroke volume)

AcclimatizationAcclimatization• Hematological

– Decreased plasma volume– Increased hematocrit (?)– Increased hemoglobin– Increased # of RBCs– Possible increase in capillary beds (?)– Increased 2,3 DPG– Increased mitochondrial density– Increased aerobic enzymes in muscle

AcclimatizationAcclimatization• Catecholamine Response

– Nor-epinephrine• Regulates HR, BP, SV, Vasc Resistance and

substrate use.• Increases for 7 days and then stabilizes.

– Epinephrine shows little to no increase

Acclimatization Acclimatization (Acid Base Balance)(Acid Base Balance)

• Hyperventilation leads to a decrease in carbon-dioxide thus increasing pH of all body fluids. This blunts respiratory control.

• Body begins to excrete base through renal tubules to normalize pH

• This increases resp. sensitivity and allows for greater hyperventilation.

Acclimatization Acclimatization (Acid Base Balance)(Acid Base Balance)

• This decrease in “base” creates a loss of the absolute alkaline reserve inhibiting the bodies acid buffering ability.

• This is made up for by a decrease in acid production as a result of reduced CNS drive, a decrease in intracellular ADP and a reduction in epinephrine output.

Acclimatization ScheduleAcclimatization Schedule• Rapid ascent 0 to 7,500 ft 2 weeks to adjust.• then 1 week per 2,000 ft up to 15,000 ft.

Riiiiight!

Climb to camp altitudeActive acclimatizationMove to next campRepeat as necessarySummitGet off the top!

Altitude Related IllnessesAltitude Related Illnesses• All are exacerbated by:

– Speed of ascent– Altitude– Health of Individual– General susceptibility of individual

Altitude Related IllnessesAltitude Related Illnesses• Slow Ascent Symptoms

– Diminished exercise capacity– Shortness of breath– Elevated HR– Cheyne-Stokes (irregular nighttime breathing)

Altitude Related IllnessesAltitude Related IllnessesRapid AscentRapid Ascent

• Acute Mountain Sickness (AMS)– Most common alt disorder– Can appear within 2 hours of ascent– Headache– Insomnia– Irritability– Weakness– Vomiting– Tachycardia– Breathing problems

Altitude Related IllnessesAltitude Related IllnessesRapid AscentRapid Ascent

• High Altitude Pulmonary Edema (HAPE)– 12 to 96 hours of ascent– Can be treated on site but reduction in

elevation is best

Altitude Related IllnessesAltitude Related IllnessesRapid AscentRapid Ascent

• High Altitude Cerebral Edema (HACE)

• Results from vasodilatation, increased capillary hydrostatic pressure.

• Must descend to accurately diagnose and treat.

Altitude Related IllnessesAltitude Related IllnessesRapid AscentRapid Ascent

• Chronic Mountain Sickness (CMS)– Can occur after months or years at altitude.

• Polycythemia• Genetically linked EPO response to stress.

Altitude Related IllnessesAltitude Related IllnessesRapid AscentRapid Ascent

• High Altitude Retinal Hemorrhage (HARH)– All climbers experience over 21,000 ft– Hemorrhage of the macula results in vision

loss.

NOTE – Eye Surgery

Body Composition and NutritionBody Composition and Nutrition

Muscle Atrophy and weight loss occur at altitude.

Depressed appetite

Dehydration

Increase BMR

Increased energy output

EAT, DRINK AND BE MERRY.

Body Composition and NutritionBody Composition and Nutrition

• Hypohydration– Increased respirations – dehydration– Low Relative Humidity at altitude– Greater loss in fecal matter– Less absorption in gut– Inadequate fluid intake

• Low desire• Difficult to obtain

Physical Performance at Physical Performance at AltitudeAltitude

• Max strength is unaffected

• Capacity for repeated contractions is progressively impaired

• Endurance is initially decreased but improves with acclimatization.

• Decrease motor skills– What track and field records broken at

altitude?

Mental Performance at Altitude Mental Performance at Altitude • Blood flow to the brain is not compromised• Decreased short term memory

• Where did I park my car?

• Mental Acuity• Let’s see it’s “I” before “E” except after no wait

it’s…

• Judgment/Decision making• What are you thinking?

SummarySummary• As we gain alt the PO2 drops resulting in

inadequate hemoglobin saturation and a decrease in aerobic capabilities

• Ability to perform high intensity short duration (sprint) physical activity is not affected.

• Why not?• Reduced PO2 results in physiologic

responses that improve altitude tolerance.

SummarySummary• Hyperventilation and increased submax

cardiac output via elevated HR are the primary immediate responses to altitude.

• Medical problems may emerge as a result of travel to altitude.

• AMS, HAPE and HACE are the most common conditions.

SummarySummary• Acclimatization entails

– Reestablishment of acid-base balance– Increased synthesis of RBC and hemoglobin– Improved local circulation and cellular

metabolism

SummarySummary• Rate of acclimatization depends on the

elevation. Major adjustments takes about 2 weeks but may require 4 to 6 weeks at higher altitudes.

• Acclimatization does not fully compensate for the stress of altitude as a result VO2max remains depressed.

• Training at altitude provides no more benefit to sea-level performance than equivalent sea level training.