Exercise at Altitude 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? 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) O 2 % at sea level = 21% O 2 % at 22,000 ft = 21% So why do we not assimilate as much O 2 at altitude as at sea level? Decreased PO 2 results in Hypoxia. –W–What is PO 2 ? –H–How does O 2 diffuse into blood and tissues? –H–How does PO 2 effect this?

Acclimatization (adaptation to the new natural environment) IMMEDIATE Respiratory –Hyperventilation –Body Fluids become more base as a result of reduction in CO 2 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

Acclimatization LONGER 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 altitude Active acclimatization Move to next camp Repeat as necessary Summit Get off the top!

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 Illnesses Rapid 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 Illnesses Rapid 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 Illnesses Rapid Ascent High Altitude Cerebral Edema (HACE) Results from vasodilatation, increased capillary hydrostatic pressure. Must descend to accurately diagnose and treat.

Altitude Related Illnesses Rapid Ascent Chronic Mountain Sickness (CMS) –Can occur after months or years at altitude. Polycythemia Genetically linked EPO response to stress.

Altitude Related Illnesses Rapid 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 appetite Dehydration Increase BMR Increased 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 Difficult 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 –What track and field records broken 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?

Summary As we gain alt the PO 2 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 PO 2 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 VO 2 max remains depressed. Training at altitude provides no more benefit to sea-level performance than equivalent sea level training.