The interest about the mechanisms of generation and adaptation of oxygen free radicals (OFR) to exercise has increased significantly from the demonstration of its relation with the oxygen intake. The OFR are formed through the incomplete reduction of oxygen, generating species presenting high reactivity to other biomolecules, especially lipids and proteins of the cell membranes and even DNA. The injuries caused by the oxidative stress present accumulative effects, being related to several diseases such as cancer, arteriosclerosis and diabetes. The acute physical exercise furthers the increase on the formation of OFR in function of the increment on the oxygen intake. However, the physical training generates adaptations able to soften the harmful effects caused by OFR. These adaptations are related to several systems, among which the most important are the enzymatic system, composed by the superoxide dysmutase, catalase and glutathione peroxidase; and the non-enzymatic system, composed by the ceruloplasmine, the sexual hormones, co-enzyme Q, uric acid, thermal shock proteins, among others. Such adaptations, despite the controversies about the mechanisms involved, further a higher tissue resistance and oxidative challenges such as those provided by long-duration high intensity exercises. The evaluations techniques of the oxidative stress, most times are not able to detect injuries in short-duration exercises. Thus, studies of physical efforts performed for long periods or until exhaustion have been conducted. New lesion markers by OFR action have been discovered and new techniques for its determination have been created. The objective of this work is discuss the formation mechanisms of OFR and the adaptations to the chronic oxidative stress caused by physical training.
Exercise; Oxygen free radicals oxidative stress; Antioxidants; Training
