There are no studies analyzing the effect of training loads on purine metabolism during long training periods. Purpose: The study's purpose was to evaluate the effect of training load changes and subsequent detraining on purine metabolism in middle-distance runners during a 1-yr cycle. Methods: In four characteristic points of the training cycle, loads assigned to five intensity zones, pre- and postexercise plasma hypoxanthine (Hx) and uric acid, and erythrocyte Hx-guanine phosphoribosyltransferase (HGPRT) activity were determined in 11 male middle-distance runners at the national level, practicing competitive sport for 8.1 ± 0.3 yr and with a mean age of 22.3 ± 0.7 yr, body mass of 73.0 ± 3.4 kg, and body height of 180 ± 2.2 cm. Results: In the competition phase (CP), training loads in aerobic compensation and threshold zones decreased by 65.4% and by 20.5%, respectively. At the same time, anaerobic training loads increased by 132.5% in the VO2max zone and by 74.6% in the lactic acid tolerance zone. Postexercise Hx decreased significantly in CP by 6.2 µmol/L and increased in the transition phase (TP) by 17.4 µmol/L. Both pre- and postexercise HGPRT activity increased significantly in CP by 9.3 nmol/mg·h and by 4.9 nmol/mg·h, respectively, and decreased significantly in TP by 10.6 nmol/mg.h and by 12.0 nmol/mg·h, respectively. A significant uric acid increase of 54 µmol·L-1 was revealed merely in TP. Conclusions: The effect of anaerobic training on purine metabolism is significant despite of a very short total duration of anaerobic loads. Elevated preexercise HGPRT activity in CP suggests adaptation changes consisting in a "permanent readiness" for purine salvage. The detraining in TP leads to reverse adaptation changes. Probably, plasma Hx concentration and erythrocyte HGPRT activity may be considered as a useful measure of training status.
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