Exercise Physiology and Altitude Adaptation MCQs

Physiology · 27 free questions with answers & explanations.

1. A mountaineer ascends to 4500 m above sea level. After 2 weeks of acclimatization, which physiological adaptation is expected to persist?
2. A mountaineer ascends from sea level (PO₂ 160 mmHg) to 5000 m altitude (barometric pressure 405 mmHg, PO₂ ≈ 85 mmHg) over 2 weeks. Which compensatory adaptations occur in sequence to maintain oxygen delivery?
3. During maximal aerobic exercise, VO₂max is reached when further increases in workload produce no additional increase in oxygen consumption. Which factor primarily limits VO₂max in a sedentary individual?
4. During moderate-intensity exercise (60% VO₂max), which statement correctly describes substrate utilization and the hormonal milieu supporting it?
5. On acclimatisation to high altitude (e.g., 4500 m), the initial respiratory alkalosis from hyperventilation is compensated by renal HCO₃⁻ excretion. However, the sustained increase in ventilation at altitude occurs because of an adaptation in peripheral chemoreceptors. What is this adaptation?
6. At maximal exercise, the primary factor limiting VO2max in healthy, untrained individuals is:
7. Acclimatisation to high altitude (3000-4500 m) over 1-2 weeks is characterised by persistent hyperventilation despite normalised arterial pH. Which mechanism explains this paradox?
8. At high altitude, acclimatization involves an increase in 2,3-bisphosphoglycerate (2,3-BPG) in erythrocytes. What is the exact mechanism by which 2,3-BPG causes a right shift of the oxygen-hemoglobin dissociation curve?
9. At high altitude (>3500 m), a climber acclimatizes over days. A key feature of acclimatization is the rightward shift of the oxyhemoglobin dissociation curve, facilitating oxygen unloading in tissues. This rightward shift occurs primarily because:
10. During maximal aerobic exercise, cardiac output can increase from 5 L/min at rest to 20–25 L/min in trained athletes. The primary mechanism for this rise is increased heart rate; however, stroke volume also increases from ~70 mL to ~120 mL. The most important reason stroke volume increases during vigorous exercise despite reduced diastolic filling time is:
11. At high altitude (above 4,500 m), acclimatized individuals show increased 2,3-bisphosphoglycerate (2,3-BPG) in red blood cells. Although this rightward shift of the Hb-O₂ curve aids O₂ release to tissues, it is paradoxically limited at extreme altitude. Which acid-base phenomenon limits the 2,3-BPG benefit at extreme altitude?
12. During maximal aerobic exercise, cardiac output can increase 4–5-fold. The mechanism accounting for the majority of the increase in cardiac output during exercise is:
13. At high altitude, hypoxia-inducible factor (HIF-1α) mediates many adaptive responses. HIF-1α is normally rapidly degraded by the proteasome. Which molecular mechanism stabilizes HIF-1α during hypoxia?
14. During maximal exercise, cardiac output can increase 5-fold. The most important mechanism by which venous return increases proportionally to maintain cardiac output via the Frank-Starling mechanism is:
15. At high altitude (above 4500 m), chronic acclimatization includes a decrease in the hypoxic ventilatory response (HVR) relative to the acute response. This 'ventilatory acclimatization' results from:
16. At an altitude of 5000m (PO2 ~75 mmHg), a mountaineer after 2 weeks shows which pattern of ventilatory acclimatization and its mediators?
17. During maximal exercise, oxygen consumption (VO2max) is most accurately described as being limited by which factor in healthy untrained individuals?
18. VO2 max is considered the gold standard measure of cardiorespiratory fitness. The primary limiting factor for VO2 max in sedentary individuals at sea level is:
19. At high altitude (4500 m), acclimatized mountaineers show a rightward-then-leftward shift of the oxyhemoglobin dissociation curve during the acclimatization process. Which sequential physiological changes explain this temporal pattern?
20. During maximal aerobic exercise, a trained athlete's cardiac output increases from 5 L/min at rest to 25 L/min. Which of the following best quantifies the relative contribution of heart rate vs. stroke volume to this increase, reflecting training adaptations?
21. VO2max is the gold standard measure of cardiorespiratory fitness. In a highly trained endurance athlete, which is the PRIMARY limiting factor for VO2max?
22. An endurance-trained athlete has a resting cardiac output of 5 L/min and a maximum cardiac output of 35 L/min. An untrained individual has comparable cardiac outputs of 5 L/min and 20 L/min, respectively. The trained athlete's superior maximal cardiac output is primarily due to which adaptation?
23. At an altitude of 4500 m, the barometric pressure is approximately 430 mmHg. The inspired PO2 (PiO2) after humidification is approximately (assuming water vapour pressure = 47 mmHg):
24. The VO2max (maximal oxygen uptake) is the gold standard of aerobic fitness. The primary limiting factor for VO2max in healthy, trained individuals at sea level is:
25. VO2 max is considered the gold standard measure of cardiorespiratory fitness. Which physiological variable is the PRIMARY determinant of VO2 max, according to the Fick principle?
26. At high altitude (4500 m), a mountaineer has PaO2 = 48 mmHg and PaCO2 = 28 mmHg after 5 days acclimatisation. Her hemoglobin is now 17 g/dL. Which acclimatisation response most directly increases O2 delivery to tissues in the FIRST 24 hours (before erythropoiesis becomes significant)?
27. At high altitude (4500 m), a climber's PaO2 is 45 mmHg. Comparing his Hb-O2 dissociation curve to a sea-level resident, the climber's curve is shifted: