All volunteers were allowed to drink water ad libitum. At the end of the trials, healthy control subjects were free to leave the CCG-203971 laboratory. In contrast, to minimize the risk of late-onset hypoglycemic events, patients were kept under supervision of a physician trained in diabetes until the following morning. Patients received their usual insulin doses and meals for lunch and dinner and were allowed to sit quietly in an armchair while their glycemia was tested by means of reactive strips at least hourly. All the glycemic levels were recorded on appropriate forms, the analysis of which confirmed us that late-onset hypoglycemia after the trials was actually avoided in all patients. The present study first showed that a single bout of prolonged moderate intensity aerobic exercise did not increase the lipid peroxidation levels, in both patients with type 1 DM and healthy subjects, despite higher peroxidation levels were observed throughout in patients. In contrast, an increase in the anti-oxidant defence was observed at the end of the exercise in both patients and controls. Physical exercise is strongly recommended in DM patients because of its numerous health benefits, but it might also cause G3335 oxidative stress, resulting in a potentially harmful condition. Indeed, accumulating evidence suggests that oxidative cell injury caused by free radicals contributes to the development of DM complications, thus patients should avoid situations that might increase oxidative stress. Our results suggest that the 3-h exercise performed in the present study, which simulate several outdoor leisure time physical activities, although fatiguing, were not of sufficient intensity to provoke a large enough increase in free radical production to overwhelm the antioxidant defences. Conversely, other authors found that an exercise at higher intensity and/or at exhaustion increased the oxidative stress levels in type 1 DM patients. The observed constancy of the oxidative stress during the 3-h exercise provided new information on the effects of a single bout of aerobic exercise both in the general population and type 1 DM patients, which are considered more prone to oxidative stress effects.