Background: Exercise increases production of reactive oxygen and nitrogen species (RONS) via several mechanisms. Inter alia, increased blood flow during exercise exposes endothelial cells to shear stress, resulting in increased nitric oxide (NO) production. Increased oxygen consumption or hypoxia during exercise induces increased production of superoxide anion radical (O(2) (-)).
Objective: This study investigates the effects of maximal progressive treadmill exercise test on time-course of peripheral blood NO and O(2) (-) production, as well as the effect of long-term training on NO bioavailability.
Methods: Blood samples of 19 elite soccer players were gathered immediately before the test, during last 10 sec of every test stage, and during active recovery phases.
Results: Significant increase (p<0.05) in NO production (estimated through nitrites (NO(2) (-))), found between stage I (5.69 ± 1.32 nmol/ml) and basal values (5.36 ± 1.25 nmol/ml), was followed by the decrease in stage II (4.21 ± 0.42 nmol/ml) and production lower than basal to the end of the test. Significant increase (p<0.05) in O(2) (-) values was found between stage I (4.18 ± 0.77 nmol/ml) and resting values (4.01 ± 0.69 nmol/ml), and at stages V (4.24 ± 0.85 nmol/ml) and 1st phase of recovery (4.39 ± 0.92 nmol/ml).
Conclusion: The regression lines of NO(2) (-) and O(2) (-) crossed at the level of anaerobic threshold, suggesting that anaerobic threshold could be of a crucial importance not only in the anaerobic and aerobic metabolism but in mechanisms of signal transductions as well. Long-term exercise increases NO bioavailability, and there is positive correlation between NO bioavailability and maximal oxygen uptake (VO(2max)).
Keywords: Exercise; Maximal oxygen uptake.; Nitric oxide; Oxidative stress; Superoxide anion radical.