Effect of intermittent hypoxic exposure delivered via cyclic variation in altitude conditioning chamber on anaerobic physical performance in well-trained athletes

Field: Medicine (Health Sciences)

Competitive endurance athletes often participate in altitude training in an effort to improve sea-level performance (Clark, Aughey, Gore, and Hahn, 2004). Traditional altitude training involves living and training continuously at high altitude, which was hypothesized to improve sea-level aerobic performance by stimulating the training intensity and the oxygen carrying capacity of the cell (Eckardt, Boutellier, Kurtz, Schopen, Koller, and Bauer, 1989; Mizuno, Bro-Rasmussen, Mygind, Schibye, Rasmussen, and Saltin, 1990). However, chronic continuous exposure to high altitude has been shown to compromise training intensity (Rusko 1996), thus the negative effects may offset the beneficial effects of altitude training (Levine and Stray-Gundersen, 1997). Moreover, access to high altitude exposure on a regular basis is limited and expensive (Levine, 2002). Intermittent hypoxic exposure (IHE) is defined as the discontinuous exposure to hypoxia, in an attempt to reproduce the adaptative effects of altitude without sustaining the reverse impact of chronic hypoxia (Levine, 2002). According to a review of the literature by Levine (2002), IHE can be further divided into two subcategories: 1) hypoxic exposure during exercise, where the main goal is to enhance the training stimulus (e.g., "live-low, train-high" methodology), or 2) hypoxic exposure at rest where the primary goal is to elicit the acclimatization effect (e.g., "live-high, train-low" methodology). Intermittent hypoxic exposure protocols have been administered at sea level with the use of nitrogen houses, hypoxic tents, or hypobaric chambers (Wilber, 2000). Study results indicate that IHE during exercise (Casas, Casas, Pages, Rama, Richard, Ventura, Ibanez, Rodriguez, and Viscor, 2000) or at rest (Rodriguez, Ventura, Casas, Casas, Pages, Rama, Richart, Palacios, and Viscor, 2000; Katayama, Sato, Matsuo, Ishida, Iwasaki, and Miyamura, 2004) can enhance aerobic performance without eliciting the negative effects seen in traditional altitude training. Intermittent hypoxic exposure has also been proven to stimulate, 'anaerobic' adaptation to altitude training as noted by increases in 100 m sprint swim times and muscle-buffering capacity (Martino, Myers, and Bishop, 1995). Intermittent hypoxic exposure while training physically has been shown to improve Wingate anaerobic test (WAnT) results of elite triathletes (Meeuwsen, Ingrid, Hendriksen, and Holewijn, 2000). However, conflicting results have been reported with this regimen after moderate- to high-intensity training under hypoxic conditions (Truijen, Toussaint, Dow, and Levine, 2003; Morton and Cable, 2005) as the improvement in performance may be attributed to the effects of the training regimen. Results of recent studies have revealed significant improvements in anaerobic performance following passive (rest) IHE (Nummela and Rusko. 2000; Gore, Hahn, Aughey, Martin, Ashnden, Clark, Granham, Roberts, Slater, and McKenna, 2001; Roberts, Clark, Townsend, Anderson, Gore and Hahn, 2001; Beidleman, Mum, Fulco, Cymerman, Ditzler, Stulz, Staab, Robinson, Skirinar, Lewis, and Sawka, 2003). However. performance improvement criteria were determined by 400 m sprint time (Nummela and Rusko et al., 2000), and four-minute all-out cycling performance, variables which were part of the sea level weekly training regimen (Nummela and Rusko et al., 2000). In the aforementioned studies, the "live-high, train-low" protocol involved "living" at high altitude for long periods of time (range = 8 to 16.5 hours daily). Rodriguez, et al. (2000), reported that erythropoiesis was effectively stimulated after relatively short exposures at rest, in a hypobaric chamber (90 minutes per day three weeks at 5,500 m). To our knowledge, the effect of short-term intermittent cyclic hypoxic exposure on anaerobic performance has not been investigated. The purpose of this study was to investigate the effects of intermittent cyclic hypoxic exposure at rest on 30-second maximal anaerobic performance variables. We hypothesized that: there would be no significant difference in anaerobic performances before and after cyclic THE delivered via the Cyclic Variation in Altitude Conditioning (CVAC) chamber.