Author(s): SUZUKI, R., HATA, N., HIRABUKI, K., FUKUIE, M., MURATA, H., MATSUSHIMA, S., HORINO, M., TAKANO, D., SAKURAI, A., HIRASAWA, A., MATSUDA, T., SHIBATA, S. , Institution: KYORIN UNIVERSITY, Country: JAPAN, Abstract-ID: 1235

INTRODUCTION:
Reactive oxygen species (ROS) generated during exercise exert both beneficial and detrimental physiological effects depending on their levels. Moderate increases in ROS act as signaling molecules that promote adaptive responses such as enhancement of antioxidant defenses and mitochondrial adaptation, whereas excessive ROS production during strenuous or prolonged exercise may contribute to oxidative stress and cellular damage. Previous human studies have reported inconsistent findings regarding exercise-induced oxidative stress, with some studies showing increased oxidative stress after prolonged endurance exercise while others report minimal changes, likely depending on exercise intensity, duration, and training status. Moreover, most previous studies have relied on pre–post comparisons, and continuous monitoring of oxidative stress during prolonged exercise remains limited. Therefore, the present study evaluated systemic redox responses during prolonged endurance exercise using both pre–post comparisons and minute-level time-course assessment.
METHODS:
Fifteen healthy adults (N = 15; age 32.1 ± 5.9 years; 13 men and 2 women; VO₂max 42.5 ± 7.9 mL·kg⁻¹·min⁻¹, mean ± SD) performed 180 min of moderate-intensity cycling exercise at approximately 60–70% of VO₂max. Blood samples were collected at baseline, during exercise at 5, 30, 60, 90, 120, 150, and 180 min, and during the post-exercise recovery period. d-ROM was measured as an index of oxidative stress, BAP as an index of antioxidant capacity, and the BAP/d-ROM ratio as an index of redox balance. Time effects during exercise and differences from baseline were examined.
RESULTS:
d-ROM did not show a marked increase throughout exercise, and the change from baseline to recovery was not significant (267 ± 41 vs 275 ± 44 U.CARR, p = 0.272). Linear mixed model (LMM) analysis also showed no significant time effect during exercise (p = 0.076).
BAP increased significantly from baseline to recovery (1851 ± 250 vs 2058 ± 319 μmol/L, p = 0.032). Consistent with this, LMM analysis revealed a significant time effect during exercise (p = 0.003), with estimated mean BAP values gradually increasing and reaching the highest level at 180 min. The BAP/d-ROM ratio did not change significantly from baseline to recovery (7 ± 1 vs 8 ± 2, p = 0.848), and no significant time effect was observed during exercise based on LMM analysis (p = 0.138).
CONCLUSION:
During a 3-h bout of moderate-intensity exercise, oxidative load as assessed by d-ROM did not change, whereas BAP increased significantly. These findings suggest that prolonged exercise does not necessarily indicate, excessive oxidative stress, rather, antioxidant capacity may be mobilized in response to the exercise load, thereby maintaining systemic redox balance.