Background: Patients with severe asthma need to be studied separately due to differences from less severe asthma. This is the first study to carry out a wide physical evaluation of children and adolescents with severe asthma. The objective was to evaluate maximal and submaximal exercise capacity, respiratory and peripheral muscle strength in children and adolescents with severe asthma. Methods:The study included children and adolescents (6 to 18 years) diagnosed with severe asthma, controlled in the last 4 weeks. The maximal exercise capacity was measured by the modified shuttle test (MST) and submaximal by the 6-min walk test. Respiratory muscle strength was evaluated by measuring maximal respiratory pressures and the peripheral strength through a handgrip.Results: Thirty patients were included, with mean age of 10.3 years, 63% female and 46.7% overweight or obese. Patients underperformed but reached more than 80% of expected in all evaluations. There was a moderate correlation between age and body mass index (BMI) with MST, maximal expiratory pressure and peripheral muscle strength. The correlation between MST and BMI was negative. There was a strong correlation between peripheral muscle strength and age. Peripheral muscle strength also correlated moderately with respiratory muscle strength and lung function. Conclusion:Children and adolescents with severe asthma had lower maximal and submaximal exercise capacity and reduced peripheral and respiratory muscle strength. These results are slightly below normal and very similar to patients with less severe asthma, allowing us to infer that patients with severe asthma have a good functional condition when the disease is controlled.