Abstract Physical exercise is likely to alter brain function and to afford neuroprotection in several neurological diseases. Although the favorable effects of physical exercise on traumatic brain injury (TBI) patients is well known, little information is available regarding the role of free radicals in the improvement induced by physical exercise in an experimental model of TBI induced by fluid percussion injury (FPI). Thus, we investigated whether 6 weeks of swimming training protects against oxidative damage (measured by protein carbonylation and thiobarbituric acid-reactive substances-TBARS) and neurochemical alterations represented by immunodetection of α subunit and activity of Na+ ,K+ -ATPase after FPI in cerebral cortex of rats. Statistical analysis revealed that physical training protected against FPI-induced TBARS and protein carbonylation increase. In addition, physical training was effective against Na+ ,K+ -ATPase enzyme activity inhibition and α1 subunit level decrease after FPI. Pearson's correlation analysis revealed that the decrease in levels of catalytic α1 subunit of Na+ ,K+ -ATPase induced FPI correlated with TBARS and protein carbonylation content increase. Furthermore, the effective protection exerted by physical training against FPI-induced free radical correlated with the immunocontent of the catalytic α1 subunit maintenance. These data suggest that TBI-induced reactive oxygen species (ROS) generation decreases Na+ ,K+ -ATPase activity by decreasing the total number of enzyme molecules, and that physical exercise protects against this effect. Therefore, the effective protection of selected targets, such as Na+ ,K+ -ATPase induced by physical training, supports the idea that physical training may exert prophylactic effects on neuronal cell dysfunction and damage associated with TBI.