Elevated serum antioxidant capacity and plasma malondialdehyde concentration in response to a simulated half-marathon run

Purpose and Methods: Indices of antioxidant status, membrane permeability, and lipid peroxidation were investigated in venous blood immediately before and after a simulated half-marathon run. In serum, these included the ability to scavenge free radicals (total antioxidant capacity, TAC), the concentration of uric acid (UA), and the activities of creatine kinase (CK) and β-glucuronidase (βG). The plasma concentration of malondialdehyde (MDA) was used as a marker of lipid peroxidation. Data were analyzed with paired t-tests. After a standardized warm-up, 17 trained male runners (mean ± SD, age 31 ± 4 yr, peak V̇O₂ 63.2 ± 4.8 mL · kg^-1 · min^-1) each completed a self-paced half-marathon run, on a motorized treadmill. Average exercise intensity was 77.1 ± 1.0% peak V̇O₂, with a performance time of 87.1 ± 7.0 min. Results: After exercise, elevations were observed in MDA from 1.48 ± 0.39 mmol · L^-1 to 1.65 ± 0.32 mmol · L^{- 1} (P < 0.05), TAC from 475 ± 84 to 564 ± 113 mmol Trolox Eq · L^-1 (P < 0.0001), UA from 268 ± 45 to 312 ± 51 mmol · L^-1 (P < 0.001), serum cortisol concentration from 339 ± 95 to 557 ± 157 nmol · L^-1 (P < 0.01), CK from 98 ± 67 to 133 ± 89 IU · L^-1 (P < 0.0001), and βG from 15.39 ± 5.34 to 17.05 ± 5.7 Sigma Units · mL^-1 (P < 0.001). Conclusions: The rise in TAC did not prevent exercise-induced lipid peroxidation and muscle damage as both MDA and CK were elevated after exercise. This may indicate inadequacies in the antioxidant defense system during the half-marathon run.