Hypoxia & Hyperoxia

Abstract

In altitude populationsacclimatization (physiological changes during sojourn) and adaptation (genetic variation) are important for survival and performance capacity. Here we compare physiological differences during exercise in highlanders in South America, Asia (Tibet and Nepal) and East Africa (Ethiopia and Kenya). During short-lasting activities, the reduced air friction is an advantage. During longer exercise duration, the reduced maximal aerobic metabolism is limiting. During submaximal exercise, various compensatory mechanisms are effective: increased ventilation, reduction of respiratory alkalosis by the kidneys, growth of the lungs during childhood with improved diffusion capacity, rise of hemoglobin mass and concentration (only in America), changes in hemoglobin-oxygen affinity, reduction of muscle fiber magnitude shortening the distance for O2 diffusion, reduction of mitochondrial volume corresponding to the lowered O2 consumption. There are genetic differencesin populations living longer at altitude than South Americans. In Tibetans hemoglobin concentration does not rise up to 4000m (reduction of the effect of Hypoxia Inducible Factor 2), while more nitric oxide facilitates ventilation and perfusion. In some of the Ethiopians, arterial O2 saturation is astonishingly high; an increased oxygen affinity of hemoglobin might be the cause. The high exercise capacity of Ethiopians and Kenyans living between 2200 and 2900m seems not to be mainly an altitude effect, but the result of intense physical training since childhood and of biomechanical factors (e. g. mass and length of legs). KEY WORDS: Hypoxia, Physical Training, Genetics