Exercise at Altitude

1. 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?

2. How high is high? • Moderate = <12,000 ft • High = 12,000 to 18,000 ft • Very High = >20,000 ft

3. Stress of Altitude • The 4 “H”s • Hypoxia • Hypothermia • Hypoglycemia • Hypohydration Additionally • Suppressed Immune System • Suppressed Emotional State

4. 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?

5. 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

6. 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)

7. 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

8. 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

9. 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.

10. 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.

11. 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!

12. Altitude Related Illnesses • All are exacerbated by: • Speed of ascent • Altitude • Health of Individual • General susceptibility of individual

13. Altitude Related Illnesses • Slow Ascent Symptoms • Diminished exercise capacity • Shortness of breath • Elevated HR • Cheyne-Stokes (irregular nighttime breathing)

14. 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

15. 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

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

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

18. 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

19. 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.

20. 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

21. 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?

22. 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?

23. 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. • Why not? • Reduced PO2 results in physiologic responses that improve altitude tolerance.

24. 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.

25. Summary • Acclimatization entails • Reestablishment of acid-base balance • Increased synthesis of RBC and hemoglobin • Improved local circulation and cellular metabolism

26. 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.