BackgroundType 1 diabetes patients have a higher risk of developing hypoglycemia or hyperglycemia during physical activity, which may compromise their safety during exercise but results regarding the exercise capacity of patients with type 1 DM when compared to control subjects have been contradictory.AimTo evaluate if type 1 diabetes affects the capacity of adolescents to exercise.MethodsThe study enrolled 37 adolescents in stage 2–4 of the Tanner scale, aged from 10 to 14 years, 21 with type 1 diabetes and 16 without any chronic diseases. All subjects performed an incremental submaximal exercise test in a cycle ergometer. At the end of every test stage, glycemia and blood lactate levels were measured. During the test, heart rate was monitored and the Borg rating of perceived exertion (RPE) was used to assess fatigue.ResultsThe two groups displayed no significant differences in anthropometric variables. The response to exercise, as evaluated by Borg RPE (p = 0.829), maximum oxygen uptake (VO2max) (p = 0.977), heart rate (p = 0.998), maximum load (p = 0.977), absolute load at lactate threshold (p = 0.377) and relative load at lactate threshold (p = 0.282), was also similar between the control and the type 1 diabetes group. Finally, there were no significant correlations between HbA1c levels, VO2max, duration of disease and pre-test glycemia levels.ConclusionsWe detected no significant differences in lactate threshold, VO2max and heart rate during exercise between healthy adolescents and non-sedentary adolescents with type I diabetes, indicating that both groups had similar physical fitness and, therefore, that type 1 diabetes is not an obstacle for physical activity. This study was approved by the ethical committee of the Hospital Israelita Albert Einstein (Ethical Committee Number: 53638416.9.0000.0071) and free and informed consent was obtained from all participants and their legal representatives.