{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,5]],"date-time":"2026-05-05T02:10:20Z","timestamp":1777947020948,"version":"3.51.4"},"reference-count":0,"publisher":"S. Karger AG","license":[{"start":{"date-parts":[[2009,1,20]],"date-time":"2009-01-20T00:00:00Z","timestamp":1232409600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/karger.com\/pages\/terms-and-conditions"},{"start":{"date-parts":[[2009,1,20]],"date-time":"2009-01-20T00:00:00Z","timestamp":1232409600000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/karger.com\/pages\/terms-and-conditions"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Respiration"],"abstract":"<jats:p>High-altitude exposure impairs both maximal aerobic and anaerobic (lactic and alactic) performances. The maximal aerobic power (VO&lt;sub&gt;2max&lt;\/sub&gt;) decreases exponentially with increasing altitude. At 5,350 m, a sudden rise in inspired O&lt;sub&gt;2&lt;\/sub&gt; pressure (PIO&lt;sub&gt;2&lt;\/sub&gt;) was found to raise the VO&lt;sub&gt;2max&lt;\/sub&gt; of acclimatized lowlanders from 70 to only 92% of the control sea-level value. Since the hemoglobin concentration was about 35% higher than that of the controls, hemoglobin O&lt;sub&gt;2&lt;\/sub&gt; saturation was restored to about 100% and maximal cardiac output was only 10-20% lower than at sea level, the above result can only be the consequence: (1) of a reduced muscle mass and\/or of muscle deterioration, and (2) of impaired muscle perfu-sion. In muscle biopses taken from the vastus lateralis muscles of mountaineers after a 6- to 8-week sojourn at high altitude, a reduction in the fiber cross-sectional area was found which was accompanied by a decrease in the volume density of the mitochondria and by a lower tissue oxidative capacity. In acclimatized lowlanders, the maximal blood lactate concentration after exhausting exercise was halved compared to sea-level conditions. On the other hand, the peak anaerobic power was not affected by severe hypoxia within the first 3 weeks of exposure; thereafter, it decreased by about 25% probably as a consequence of muscle detorioration. It is concluded that, whereas in acute hypoxia VO&lt;sub&gt;2max&lt;\/sub&gt; is primarily reduced by a lack of O&lt;sub&gt;2&lt;\/sub&gt;, in chronic hypoxia muscle deterioration may become an important factor contributing to the limitation of the maximal aerobic performance.<\/jats:p>","DOI":"10.1159\/000196117","type":"journal-article","created":{"date-parts":[[2009,1,21]],"date-time":"2009-01-21T11:06:40Z","timestamp":1232536000000},"page":"24-29","source":"Crossref","is-referenced-by-count":23,"title":["Muscle Energetics and Ultrastructure in Chronic Hypoxia"],"prefix":"10.1159","author":[{"given":"P.","family":"Cerretelli","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"127","published-online":{"date-parts":[[2009,1,20]]},"container-title":["Respiration"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.karger.com\/Article\/Pdf\/196117","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/karger.com\/article-pdf\/doi\/10.1159\/000196117","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,5,2]],"date-time":"2026-05-02T21:28:22Z","timestamp":1777757302000},"score":1,"resource":{"primary":{"URL":"https:\/\/karger.com\/article\/doi\/10.1159\/000196117"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2009,1,20]]},"references-count":0,"URL":"https:\/\/doi.org\/10.1159\/000196117","archive":["Portico"],"relation":{},"ISSN":["0025-7931","1423-0356"],"issn-type":[{"value":"0025-7931","type":"print"},{"value":"1423-0356","type":"electronic"}],"subject":[],"published":{"date-parts":[[2009,1,20]]}}}