altitude acclimatization


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altitude acclimatization

physiological adjustments that help to compensate mainly for the shortage of oxygen. When blood is inadequately oxygenated in the lungs, the hypoxic condition (low PO2) of blood and tissues stimulates changes in: (1) ventilation: increase in rate and depth of breathing brings the partial pressure of oxygen in the lungs (and therefore in the arterial blood) closer to that in the air, whilst decreasing the partial pressure of carbon dioxide ( P CO2); the resulting alkalosis is gradually corrected and the hyperventilation later diminishes; (2) cardiac output (CO): initial increase at rest, and at any level of activity, provides greater blood flow to the tissues in compensation for the lowered oxygen content of the blood. Over a few days CO decreases again for any given O2 until it has returned to sea-level values, with tissues extracting more oxygen per litre of blood (i.e. the arteriovenous difference increases); (3) oxygen transport and delivery: after an initial increase in haematocrit due to reduction in plasma volume, stimulation of erthropoietin secretion enhances red blood cell production in the bone marrow, raising the red cell count and haemoglobin (Hb) concentration in the blood; this increases the amount of oxygen that can be carried per litre of blood at the lowered saturation (but the polycythaemia increases blood viscosity). The affinity of Hb for oxygen is modified by an increase in the enzyme 2-3 DPG, causing a rightward shift in the oxyhaemoglobin dissociation curve; this assists offloading in the tissues at a any given local PO2, but can be offset by a leftward shift of the curve due to low arterial P CO2. There are also changes in cellular metabolism. The timing and effectiveness of these adjustments vary among individuals, as does tolerance of the negative effects. See also acclimation, altitude sickness, altitude training, chemoreceptors, erythropoiesis, hypoxia, partial pressure.
References in periodicals archive ?
Indeed a different composition in membrane lipids (12), a higher concentration of intracellular ATP (10), and a partial fragmentation of actin (13), have been observed in a fraction of red cells populations from mountain climbers after high altitude acclimatization and return to sea level.
Red blood cell senescence and neocytolysis in humans after high altitude acclimatization.
Whereas the optimal organization of altitude training to optimize performance at sea level is heavily discussed in the scientific community, the benefit of altitude acclimatization (about 1 to 2 weeks) for competitions at moderate altitudes above 2,000 m is well established (2).
The potential benefit of classic altitude training is that altitude acclimatization provides the stimulus for both central and peripheral adaptations, as well as an additional training load compared to sea level (Bartsch and Saltin, 2008).
train at higher intensities) due to adaptations from altitude acclimatization.
The average HR per watt decreased after simulated altitude acclimatization via rebreathing, or, the efficiency of HR was improved in the TRT group.