C H A P T E R 11

1. C H A P T E R 11 EXERCISE At High Altitude and MICROGRAVITY ENVIRONMENTS

2. Conditions at Altitude w Defined as at least 1,500 m (4,921 ft) above sea level w Reduced barometric pressure (hypobaric) w Reduced partial pressure of oxygen (PO2)** w Reduced air temperature w Low humidity w Increase in solar radiation intensity

3. Highest Peak in Texas: Guadalupe Peak – 8,749 feet http://www.americasroof.com/tx.shtml http://www.srh.noaa.gov/maf/HTML/Gdppeak.html oC oF

4. CONDITIONS AT VARIOUS ALTITUDES oC oF

5. Effects of Altitude on PO2 Gradient The reduction in PO2 at altitude decreases the partial pressure gradient between the blood and the tissues and thus lowers oxygen transport. This primarily explains the decrease in endurance sports performance at altitude. PO2 at sea level = 760 mmHg  0.2093 = 159 mmHg PO2 at 8,000 ft = 564 mmHg  0.2093 = 118 mmHg Sea Level8,000 ft Arterial PO2100 mmHg 60 mmHg Muscle PO240 mmHg40 mmHg ΔPO2 60 mmHg 20 mmHg (diffusion gradient)

6. . w As PO2 decreases above 1600 m, VO2max decreases linearly. Acute Respiratory Responses to Altitude wPulmonary ventilation increases because of chemoreceptor response to hypoxia (low arterial PO2) – body fluids become more alkaline from blowing off CO2. This is followed by increased excretion of bicarbonate by the kidneys. w Pulmonary oxygen diffusion decreases because of ↓ ΔPO2. w Oxygen transport is slightly impaired; reduced Hb saturation from 98% at sea level to 90-92% at 8,000 ft. w Thus, VO2max is impaired once you are above 1,600 m.

7. . CHANGES IN VO2MAX WITH ALTITUDE Denver – 5280 feet

8. . Altitude does not affect VO2max until approximately 1,600 m (5,294 ft). Above this level, the decrease in VO2max is approximately 8-11% for every 1,000 m (3,281 ft). . Effect of Altitude on Aerobic Capacity

9. . VO2MAX RELATIVE TO PO2

10. . w Initial increase in HR and Q during submaximal work to compensate for lower PO2; SV is decreased with plasma volume decline . w Decrease in HR (because of reduced exercise capacity), SV, and Q during maximal work, which contributes to the decrease in VO2max. Acute Cardiovascular Responses to Altitude w Initial decrease in plasma volume (more red blood cells per unit of blood, thus more oxygen per unit of blood) because of increased ventilation and low humidity

11. Acute and Chronic Cardiovascular Responses to Altitude during Submaximal Exercise Brooks et al., Exercise Physiology, 2000

12. Metabolic Responses to Altitude w Increase in anaerobic metabolism w Increase in lactic acid production during submaximal work • Less lactic acid production at maximal work rates at altitude than at sea level because it isn’t possible to exercise at as high an intensity. • You won’t be able to train at an intensity than you normally could have at sea level.

13. Acute and Chronic Metabolic Responses to Altitude during Submaximal Exercise Brooks et al., Exercise Physiology, 2000

14. Acute and Chronic Catecholamine Responses to Altitude during Submaximal Exercise Brooks et al., Exercise Physiology, 2000

15. w Endurance athletes can prepare for competitions at altitude by performing high-intensity endurance training at any elevation to increase their VO2max. . Key Points Performance at Altitude wAt altitude, endurance activity is affected the most due to the reduced oxygen transport because of low PO2. wAnaerobic sprint activities that last 2 min or less are the least affected by altitude. w The thinner air at altitude provides less aerodynamic resistance and less gravitational pull, thus potentially improving sprinting, jumping, and throwing events.

16. . w Decrease in VO2max with initial exposure does not improve much Acclimatization to Altitude w Increase in number (volume) of red blood cells (RBC) w Short term decrease in plasma volume, later reversed wIncrease in RBC, hemoglobin, and blood viscosity w Decrease in muscle fiber areas and total muscle area, therefore shorter O2 diffusion distances from capillaries to muscle fiber mitochondria w Increase in capillary density w Increase in pulmonary ventilation

17. Hb CONCENTRATIONS AT ALTITUDE College Station – 362 feet Denver – 5280 feet

18. Altitude Training for Sea-Level Performance w Increased red blood cell mass w Not proven that altitude training improves sea-level performance w Difficult to study since intensity and volume are reduced at altitude – thus, what you gain in elevated RBC, you lose because of reductions in training intensity w Live at high altitude and train at lower altitudes—living high/training low

19. LIVING HIGH, TRAINING LOW 3,000 km time was tested at sea level before and after 27 days of training at 4,100 ft. and living at 8,200 ft. The mean increase in 3,000 km time was 1.1%, and the mean increase in VO2max was 3.2%.

20. . w Increase VO2max at sea level to be able to compete at a lower relative intensity while at altitude Training for Optimal Altitude Performance w Compete within 24 hours of arrival to altitude, or w Train at 1,500 to 3,000 m above sea level for at least 2 weeks before competing

21. Acute Altitude Sickness w Nausea, vomiting, dyspnea, insomnia w Appears 6 to 96 h after arrival at altitude w May result from carbon dioxide accumulation w Avoid by ascending no more than 300 m (984 ft) per day above 3,000 m (9,843 ft)

22. Microgravity Environments w 1 g is the standard acceleration produced by gravity. w Microgravity describes conditions where gravitational force is less than 1 g. w Microgravity is used to describe conditions in space that aren't always 0 g. wThe effects of microgravity on the body are similar to the effects of detraining and aging.

23. Physiological Alterations from Microgravity w Muscle atrophies and strength decreases w Cross-sectional areas of ST and FT fibers decrease wBone mineral content in weight-bearing bones decreases* w Plasma volume decreases w Transient cardiac output and arterial blood pressure increases • Weight decreases (nearly 50% of the decrease from fluid loss) • Orthostatic stress upon return to earth: failure to maintain blood pressure because of pooling of blood in the legs

24. How Do We Study Microgravity? w We simulate a microgravity environment

25. Effects on Skeletal Muscle of Bed Rest Versus Space Flight Changes in cross-sectional area in fibers after 30 days of bed rest

26. Bone Mineral Changes in Cosmonauts during Spaceflight Bone mineral changes in the radius, a non-weight-bearing bone

27. Bone Mineral Changes in Cosmonauts during Spaceflight Bone mineral changes in the tibia, a weight-bearing bone

28. . MICROGRAVITY AND VO2MAX 3 astronauts in Skylab 4 – increased because they actually increased their exercise training while in space

29. Exercise as a Countermeasure to Detrimental Effects of Space Travel Research shows that exercise during space-flight may be an effective countermeasure to prepare astronauts for successful adaptation on return to earth. The type and amount of exercise that produces the best results is still under debate. Because of this, a number of exercise physiologists are leaders in NASA-related research into countermeasures to the deterioration that occurs during space travel.

30. Exercise as a Countermeasure to Detrimental Effects of Space Travel