Exercise at Altitude(where the air is rare)

Who performs better at a bike race in San Francisco… the athlete who trains at altitude, or the athlete who trains sea level?

Why?

How high is high? (Dude) Moderate = <12,000 ft High = 12,000 to 18,000 ft Very High = >20,000 ft

Stress of Altitude The 4 “H”s

Hypoxia Hypothermia Hypoglycemia Hypohydration

Additionally• Suppressed Immune System• Suppressed Emotional State

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 (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

AcclimatizationLONGER 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)

Acclimatization 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

Acclimatization 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 (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 (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 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 outta Dodge

Altitude Related Illnesses All are exacerbated by:

Speed of ascent Altitude Health of Individual General susceptibility of individual

Altitude Related Illnesses Slow Ascent Symptoms

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

Altitude Related IllnessesRapid 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 IllnessesRapid 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 IllnessesRapid Ascent High Altitude Cerebral Edema

(HACE) Results from vasodilatation,

increased capillary hydrostatic pressure.

Must descend to accurately diagnose and treat.

Altitude Related IllnessesRapid Ascent Chronic Mountain Sickness (CMS

Can occur after months or years at altitude.• Polycythemia• Genetically linked EPO response to stress.

Altitude Related IllnessesRapid 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 Nutrition

Muscle Atrophy and weight loss occur at altitude.

Depressed appetiteDehydrationIncrease BMRIncreased energy output

EAT, DRINK AND BE MERRY.

Body 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• Pain in the butt to obtain

Physical Performance at Altitude Max strength is unaffected Capacity for repeated contractions is

progressively impaired Endurance is initially decreased but

improves with acclimatization. Decrease motor skills

Why are track and field records broken at altitude?

Mental Performance at Altitude (Dumb and Dumber)

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 in the hell are you thinking?

Summary 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.

Reduced PO2 results in physiologic responses that improve altitude tolerance.

Summary 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.

Summary Acclimatization entails

Reestablishment of acid-base balance Increased synthesis of RBC and

hemoglobin Improved local circulation and cellular

metabolism

Summary 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.