INTRODUCTION: Among elite level endurance athletes hypoxic training became increasingly popular during the last decades. However the effectively in terms of improving the performance under normoxic conditions is still doubtful, especially by using the intermittent hypoxic training design. Recent studies show an enhancing effect of high intensity interval training under hypoxic (HIITH) conditions on repeated sprint ability (1). So we questioned whether HIIT under hypoxic compared to normoxic conditions may lead to a greater acute regenerative capacity during a set of four minutes of high intensive exercise. The ability to regenerate is one major factor for competing successfully in sports like Paralympic cross country sprint events, where athletes perform three to five time trails separated by 20 min breaks. METHODS: 10 endurance athletes were blinded and randomly divided into a hypoxic (HG FiO2 15± 0, 4 %) and normoxic (NG FiO2 19, 7± 0, 6 %) group. Ahead and after the training period performances tests were conducted on a cycle ergometer which consists of a ramp test followed by three four minutes time trails (TT) with a break of 20 minutes between each trail. VO2max, heart rate (HR) and tissue saturations index (TSI) detected at the musculus vastus lateralis were measured. The HIIT consists two sessions per week for three weeks. The session were built of 10 min of low intensity cycling followed by 12 for the first four sessions respectively 14 "15 sec. all-outsprints" in for the last two bouts interrupted by a break of 45 sec. RESULTS: VO2max increased by 1, 0 (pre 50, 0; post 51 (ml/kg/min)) for NG and 2, 0 (pre 53, 0; post 55 (ml/kg/min)) the HG respectively. During the breaks between the TTs HR decreases faster compared to pre values for both groups (6 ± 2 (b/min) NG; 3 ± 3 (b/min) HG). For TSI were no differences detected between both groups. CONCLUSION: HIIT under hypoxic conditions compared to identical trainings under normoxic conditions leads to a greater increase in VO2max, but isn´t advantageous in terms of an improved TSI or an acute regenerative capacity during a set of TT. These findings could base on the ineffective training load or the location of the post test, which may have displayed different results when conducted ten days after the end of the trainings period compared to six. --- The hosting University of Jyväskylä is planning to publish conference proceedings "Science and Nordic Skiing III". In case you are interested in this publication please contact the editors (Anni Hakkarainen anni.s.j.hakkarainen@jyu.fi) to become registered for the book.
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