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Exposure to hypoxia is associated with a significant increase in EPO concentration within the first two days. Therefore, it was assumed that this effect leads to a stimulation of erythropoiesis with a subsequent increase in Imitrex online. However, controversial results on tHb-mass were published in the last decades showing either no increase or augmentations of more than 10%. These differences can be attributed to different altitude exposure patterns, but also to the lack of sensitive methods to determine tHb-mass. With the availability of the “optimized CO-rebreathing method” many studies were performed recently, which are mainly related to endurance athletes.

Schmidt & Prommer (2008, 2010) showed that although the response to altitude is very individual a mean increase of ~6% can be achieved in trained athletes with conventional altitude training but also with the concept Live-High Train-Low as long as the altitude is > 2100m and the hypoxic exposure is at least 3 weeks for > 14h/day. In case the altitude is lower (e.g. 1816m) no significant differences in tHb-mass were found in elite cyclists (Pottgiesser et al. 2009). In less endurance trained athletes (short and middle distance runners), however, repetitive altitude sojourns at low altitudes (1300m and 1650m for 42 days in total) also yield increases of ~5% (Frese & Friedmann-Bette 2010).
The effects of repetitive altitude training camps are of practical importance since athletes not always have the possibility to stay more than 3 weeks at altitude. A combination of four 2-week blocks, living and training at 1350m for 2 x 2 weeks and living at 2600m and training at 600m for 2 x 2 weeks also increased tHb-mass by 3.6% in elite swimmers (Robertson et al. 2010a). Also two 3-week blocks living at 3000m for ~14h/day and training at lowlands (600m) augmented tHb-mass by 4.2% in elite runners (Robertson et al. 2010b).

The same magnitude in tHb-mass increase (4.3%) is achieved in middle distance runners by performing just one 3-week block of living high and training low (3000m, >14h/day) but with an additional hypoxic training (4 times per week) at 2200m (Robertson et al. 2010c). Clark et al. (2009) calculated the weekly rate of increase in tHb-mass during a 3 week live-high train-low (3000m, >14h/day) camp in elite cyclists and found an average of 1% per week or 1% per 100h. Measurable increases, however, do not occur before 2 weeks at altitude.

In endurance athletes who are chronically exposed to altitude augmented tHb-mass is expected due to the continuous hypoxic environment. This is true for Colombian elite cyclists living and training at 2600m. They show 11% higher tHb-mass than elite cyclists from sea level (Schmidt et al. 2002). In Kenyan runners from 2100m, however, tHb-mass is the same as in German runners (~14g/kg) although a hypoxic effect can even so be identified. A six week sojourn of these runners at low altitude (350m) reduced tHb-mass by ~6% although training intensity and volume where maintained (Prommer et al. 2010). It seems that East Africans have developed different altitude adaptation strategies within their evolutionary history compared to Amerindians.