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Performing at altitude
Published in R. C. Richard Davison, Paul M. Smith, James Hopker, Michael J. Price, Florentina Hettinga, Garry Tew, Lindsay Bottoms, Sport and Exercise Physiology Testing Guidelines: Volume I – Sport Testing, 2022
Mike Stembridge, Charles R. Pedlar
For over 100 years, we have known that exposure to high altitude presents a significant challenge to the human body, particularly during exercise (West et al., 2007). Due to the nature of our atmosphere, the partial pressure of oxygen falls (hypoxia) as we ascend, such that by 5000 m above sea level (severe altitude), there is approximately half the amount of oxygen in the air as at sea level. Given that even mild elevations (500–900 m) can result in a decrease in aerobic performance (Gore et al., 1996), optimal preparation for any event held above sea level is essential. This chapter will summarise our current understanding of how to prepare for performance at altitude and provide guidance for the safe ascent to higher elevations.
Pregnancy
Published in Michelle Tollefson, Nancy Eriksen, Neha Pathak, Improving Women's Health Across the Lifespan, 2021
Nancy L. Eriksen, Kristi R. VanWinden, Anne Bingham, John McHugh
There are limited studies with few subjects on exercise and pregnancy at high altitude. Available studies show that acute exposure up to 2500 meters with moderate duration exercise poses little risk to mother and fetus during the third trimester of a normal pregnancy.159 General recommendations for exercise at high altitude include adequate hydration, allowing acclimatization to altitudes more than 2,500 m for the first 4–5 days of exposure, limiting intensity to the “talk test”, and being well informed regarding the symptoms of acute mountain sickness. Preexisting conditions such as hypertensive diseases of pregnancy and/or fetal growth restriction are considered contraindications for traveling to or exercising at high altitude after 20 weeks’ gestation.159,160
Geography
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
Although there is no precise definition of “high altitude,” the term is generally applied to elevations above 2500–3000 m, as this is the altitude range at which as most individuals manifest characteristic anatomic, biochemical, clinical, and physiological changes. There is considerable interindividual variation, however, and some people are affected at altitudes as low as 2000 m. The purpose of this chapter is to describe the geography of some of the major mountainous areas of the world. After a brief description of the primary high altitude regions in which people reside, the chapter considers the people, terrain, climate, and socioeconomic features of these regions with a focus primarily on two of the major high altitude regions of the world in which people reside on a permanent basis, the Himalaya and Andes Mountains.
Relationship between blood–brain barrier changes and drug metabolism under high-altitude hypoxia: obstacle or opportunity for drug transport?
Published in Drug Metabolism Reviews, 2023
Guiqin Liu, Xue Bai, Jianxin Yang, Yabin Duan, Junbo Zhu, Li Xiangyang
Our prior research has demonstrated that high-altitude hypoxic conditions have certain effects on drug metabolism pharmacokinetics, drug metabolizing enzymes and drug transporters in the blood, liver and intestine of rats. However, studies on the blood–brain barrier and drug metabolism in hypoxic conditions have rarely been reported, and the blood–brain barrier mediates the effects of high-altitude hypoxia on drug metabolism through a multifactorial mechanism of regulation by drug transporters and drug metabolizing enzymes, transcription factors, inflammatory factors and nuclear receptors, and there is no conclusive evidence as to whether the change in expression inhibits or facilitates drug transport across the blood–brain barrier, and extensive experiments are still needed to verify this. Although it is challenging to clarify the effects of blood–brain barrier-mediated high-altitude hypoxia on central nervous system drug transport, knowledge of the structural and functional changes in the blood–brain barrier in hypoxia under high altitude conditions can help explain the diagnosis and prognosis of brain diseases as well as develop rational pharmacological and non-pharmacological intervention strategies to facilitate the transport of central nervous system drugs to the blood–brain barrier.
Phospholipid metabolites of the gut microbiota promote hypoxia-induced intestinal injury via CD1d-dependent γδ T cells
Published in Gut Microbes, 2022
Yuyu Li, Yuchong Wang, Fan Shi, Xujun Zhang, Yongting Zhang, Kefan Bi, Xuequn Chen, Lanjuan Li, Hongyan Diao
Altitude sickness is a common high-altitude clinical syndrome after exposure to low-pressure and low-oxygen environments and is especially common when individuals who typically reside in plains areas quickly enter plateau areas over 2500 meters above sea level.2 Shortness of breath and central nervous system symptoms such as headache and dizziness are the main symptoms of acute altitude sickness, which can lead to life-threatening high altitude pulmonary edema and high altitude cerebral edema if left untreated.1 However, affected individuals can also experience gastrointestinal symptoms such as nausea, vomiting and diarrhea after entering plateau areas, which may further worsen dyspnea, dizziness and headache. Although increasing evidence indicates that intestinal mucosal injury is the main cause of gastrointestinal dysfunction, the pathogenesis of gastrointestinal reactions related to high altitude is still unclear.
Insight into the role of myokines and myogenic regulatory factors under hypobaric hypoxia induced skeletal muscle loss
Published in Biomarkers, 2022
Sukanya Srivastava, Richa Rathor, Som Nath Singh, Geetha Suryakumar
Skeletal muscles are highly dynamic and plastic organ primarily consisting of myofibers and multinucleated cells that have a regenerative capacity due to the presence of satellite cells. The ability to maintain the plasticity of skeletal muscles allows it to acclimatize and cope with the adverse conditions, by preserving it structural, metabolic and functional properties. The extreme environmental conditions at high altitude enforce several metabolic, physiological and biochemical changes, hence resulting into skeletal muscle atrophy and disturbing the muscle metabolism and regenerative capacity. Skeletal muscle secretes myokines in response to muscle contraction further allowing a cross talk between muscle and other organs. The HH at high altitude regulate myokines, myogenic regulatory factors as well as the energy sensing pathways, thus signifying the adaptive responses of skeletal muscle mass proteins during initial exposure to HH. However, a reduced regeneration and repair capacity of skeletal muscles were observed via activation of several degradation and catabolic pathways during prolonged HH exposure.