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aim of the present study was to examine the influence of intermittent
hypoxia at rest and in combination with long-term high-intensity swimming
exercise on lipid peroxidation and antioxidant defense system adaptation
in skeletal muscles differing in fiber type composition. High-intensity
chronic exercise was performed as swimming training with load that
corresponded to ~ 75 % VO2max (30 min·day-1,
5 days·wk-1, for 4 wk). Intermittent hypoxic training (IHT)
consisted of repeated episodes of hypoxia (12%O2, 15 min),
interrupted by equal periods of recovery (5 sessions/day, for 2 wk).
Sessions of IHT were used during the first two weeks and during the
last two weeks of chronic exercise. Oxidative (red gastrocnemius and
soleus, mix) and glycolytic (white gastrocnemius) muscles were sampled.
Our results indicated that high-intensity swim training in combination
with sessions of IHT induced more profound antioxidative adaptations
in skeletal muscles than the exercise training only. This adaptation
has muscle fiber type specificity and is reflected in significantly
elevated superoxide dismutase and catalase activities in highly oxidative
muscle only. Training adaptation of GSH system (reduced glutathione
content, activities of glutathione reductase, glutathione peroxidase,
NADPH-supplying enzyme glucose-6-phosphate dehydrogenase) occurred
both in slow- and fast-twitch muscles. However, this process was more
effective in oxidative muscles. IHT attenuated the increase in TBARS
content induced by high-intensity swimming training. The test on exercise
tolerance demonstrated a significant elevation of the swimming time
to exhaustion after IHT at rest and after IHT in conjunction with
high-intensity exercise in comparison with untrained and chronically
exercised rats. These results confirmed that sessions of IHT might
improve exercise tolerance and increase maximal work capacity.
KEY
WORDS: Intermittent hypoxic training, swim training, oxidative
stress, antioxidative system, adaptation, muscle fiber type.
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