Aim. To evaluate the functional condition of skeletal muscles in children with type 1 diabetes (T1D), according to the duration of disease based on studying static and dynamic physical endurance. Materials and methods. 76 children with T1D from 11 to 17 years old were examined. The first group included 20 kids with the duration of diabetes less than 1 year. The second group – 27 patients with T1D from 1 to 5 years. The third group – 29 kids with T1D over 5 years. The group of control included 16 conventionally healthy children. Static muscular endurance with evaluation of total static muscular endurance (TSME) and dynamic muscular endurance with evaluation of wrist strength index (WSI) were evaluated. The index of muscle quality (IMQ) was evaluated too. Results. The greater duration of T1D was accompanied by the redistribution of percentage ratio of body components. The TSME was decreasing alomg with increase of T1D duration. Reverse correlation between glycated hemoglobin and TSME (r = -0.50; P < 0.05) was shown. The dynamic endurance revealed the progressing decrease of WSI before and after the physical exertion in children with T1D in comparison with the control group. The revealed peculiarities of functional condition of muscles were connected with TSME (r = +0.43, P < 0.05) and IMQ (r = +0.52, P < 0.05). Conclusions. Functional condition of skeletal muscles in children with T1D is characterized by decrease of static and dynamic muscular endurance. The first signs of changes are observed over the first year of disease and progress as the duration of a disease increases and leads to decrease of mucle mass and diabetic myopathy developing. The major factor contributing the worsening of functional condition of muscles is insufficient glycemic control.