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Acclimatization
Published in Andrew M. Luks, Philip N. Ainslie, Justin S. Lawley, Robert C. Roach, Tatum S. Simonson, Ward, Milledge and West's High Altitude Medicine and Physiology, 2021
Andrew M. Luks, Philip N. Ainslie, Justin S. Lawley, Robert C. Roach, Tatum S. Simonson
To mountaineers, acclimatization is the process by which they become more comfortable at altitude and find they can perform better than when they first arrived (Houston 1955; Roach 2019). The concept is nicely encapsulated by a statement from Charles Houston (1955), who, following decades of experience climbing at very high altitudes, wrote: “There is an altitude frontier beyond which humans cannot become accustomed to oxygen lack, but the approach to that frontier … is made possible by acclimatization—the process of becoming accustomed to an environment foreign to the organism.” For individuals traveling to high altitude, acclimatization prevents or alleviates symptoms and signs of acute altitude illness and restoration of some of the exercise performance lost on arrival at altitude (Latshang et al. 2013; Subudhi et al. 2014), whereas for physiologists, altitude acclimatization is, strictly, the sum of all the beneficial changes in response to altitude hypoxia that occur with time spent at a given altitude, and that eventually disappear on descent to low altitude. It refers only to the changes in response to hypoxia seen as beneficial as opposed to changes that result in illnesses such as acute mountain sickness (AMS), high altitude cerebral edema (HACE), or high altitude pulmonary edema (HAPE) and are considered pathological.
Exercise at altitude
Published in Robert B. Schoene, H. Thomas Robertson, Making Sense of Exercise Testing, 2018
Robert B. Schoene, H. Thomas Robertson
Both acute and chronic exposure to high altitude produce well-defined effects on physical performance. Persons travelling to altitude for work or recreation may first note altitude-related exercise symptoms around 1300 meters (or 4200 feet) and those symptoms increase progressively at higher elevations. As one ascends to higher altitudes, the fraction of oxygen in ambient air remains the same at 0.2093, whereas the barometric pressure decreases resulting in a lower oxygen content for a fixed volume of air. Thus, with ascent, the inspired partial pressure of oxygen as it enters the airways drops from the sea-level value of 150 mmHg to 130 mmHg at 1300 meters to 105 mm Hg at 3000 meters (9700 feet). Both acute and chronic adaptations take place during sojourns to altitude that help reduce the effects of the lower oxygen availability in the inspired air. These adaptations take place in all of the organ systems involved with the transport and utilization of oxygen by exercising muscle. The immediate and longer term responses to altitude acclimatization are discussed by organ system in this chapter. Finally, the effects on exercise performance and the benefits of athletic training at altitude are discussed, taking the known effects of acclimatization into account. Ventilation—immediate and ongoingCardiovascular—immediate and ongoingBlood—days to weeks and ongoingTissue—weeks to monthsExercise performanceTraining at altitude
Physiological and oxidative stress responses to intermittent hypoxia training in Sprague Dawley rats
Published in Experimental Lung Research, 2020
Megha A. Nimje, Himadri Patir, Rajesh Kumar Tirpude, Prasanna K. Reddy, Bhuvnesh Kumar
The natural countermeasures to the altitude-induced physical performance decrements and AMS are altitude acclimatization. Lowlanders who continuously reside at high altitude develop a variety of physiological adaptations during altitude acclimatization. Acclimatization to a target altitude can be induced by slow progressive ascents or continuous stays at intermediate altitudes. However, altitude acclimatization is a very time and resource consuming process and doesn’t suit to the activities which require urgent attention. Depending on the altitude to which a previously unacclimatized lowlander has descended, the time course for altitude acclimatization is 4-11 days.10 In military point of view, this altitude residency requirement drastically reduces the utilization of military personnel in rapid response military missions that exploit the air mobility capability of modern military forces to quickly deploy to an area of operations on short notice.