, 1995). Athletes are exposed to hypoxia in rooms; training is the only break from the hypoxia. In a hypoxic room, they breath with air depleted in oxygen by N2 enrichment (Koistinen et al., 2000; Gore et al., 2001) or sellekchem some oxygen is filtered out (Robach et al., 2006; Schmitt et al., 2006). These researchers recommend staying at a simulated height of �� 3000 m for at least 3h?d?1 for 1�C3 weeks. Those conditions, in which athletes who train using the IHE method, e.g. swimmers (Rodr��guez et al., 2007), closer to a high-mountain climate are those used in hypobaric chambers where a lower atmospheric pressure is present. Rodr��guez et al. (2000) suggest that IHE application prevents sport shape decrease after a sudden elevation at significant altitude, and support erythropoiesis with a simultaneous improvement of effort capabilities.

LL+TH �C live low and train high by IHT �C Intermittent Hypoxic Training �C Classified as �C LL+TH (live low and train high) �C living at sea level with altitude training (Wilber, 2007a). This AT model, in which athletes exercise in hypoxic conditions from seconds to hours for periods lasting from days to weeks (Millet et al., 2010). Hypoxia is produced artificially in rooms or hypobaric chambers as well as using hypoxicators, which enable the breathing of a gas mixture (Katayama et al., 2004). This solution was also used in swimmers (Truijens et al., 2003). Such methods simulate the atmospheric conditions present at an altitude of 2500 �C 3500 m above sea level. The interval effort in such conditions occurs in periods from 5 to 180 minutes (Wilber, 2007a).

Millet et al. (2010) show that intermittent hypoxic interval training interspersed (IHIT) is defined as a method where, during a single training session, there is an alternation between hypoxia and normoxia. The researchers claim that, in a manner similar to IHE, time spent outside the chamber, in which the IHT method is applied, might also be used for additional normal training activity, as in the case of swimmers in Truijens et al. (2003) and other athletes (Meeuwsen et al., 2001; Hendriksen et al., 2003). Another advantage of the IHT method is recovery after altitude training in sea level conditions, which prevents the occurrence of the negative symptoms of prolonged high-mountain exposure.

These circumstances do not force a reduction in the amount of physical training, and they prevent sleep perturbations and dehydration; they also enable normal alimentation. The behaviour of athletes using IHT methods results in the improvement of nonhaematological physical endurance indices, such as an increase in mitochondria density, the muscular AV-951 fiber of capillary ratio and the cross-section of muscular fibers (Vogt et al., 2001; Czuba et al., 2011). It also enables changes in the blood oxygen transport properties. These effects, however, are not always significant (Truijens et al.