The aim of our study was to investigate the effect of a single high intensity session of muscle contractions on the activity and expression of citrate synthase (CS) and of the following major antioxidant enzymes: Mn-superoxide dismutase (Mn-SOD), Cu,Zn-superoxide dismutase (Cu,Zn-SOD), catalase (CAT), and glutathione peroxidase (GPX). To accomplish this, soleus muscles of male Wistar rats were subjected to contractions using a intense electrical stimulation (ES) protocol. Soleus muscles were isolated either immediately or 1 h after the contractions and utilized for enzyme activity determination, and for analysis of gene expression by quantitative PCR. A significant increase in maximal activity (63%) and expression (80%) of CS was observed in stimulated soleus muscles, isolated 1 h after ES as compared to controls. However, this effect was not observed in muscles isolated immediately after ES. By using macroarray and Real Time RT-PCR analysis, an increase in expression of Mn-SOD, Cu,Zn-SOD, CAT, and GPX was also found. Interestingly, of these enzymes, only CAT activity was significantly increased (44%) 1 h after ES in soleus muscle. These results indicate that acute ES up-regulates activity and expression of CS and CAT in soleus muscles. This increase in expression of CAT may play an important role in counteracting the potential deleterious effects of elevated oxidative stress induced by a high oxidative demand in skeletal muscles subjected to exercise training.