**2.1. Study participants**

The study group comprised a total of 53 (27 girls and 26 boys) children and adolescents with type 1 diabetes mellitus (T1DM). Mean age was 11.8 ± 2.4 years (range 5 to 17 years); duration of diabetes was 2.8 ± 1.6 years (Table 1). All subjects lived and attended schools in Silesian Industrial Region in Poland and were recruited at the Diabetes Clinic of the Silesian Center for Child Health. They were treated with recombinant human insulin divided into daily doses, and performed self-monitoring of blood glucose on glycaemic control. The types of insulin used were: NovoRapid, Lantus, Humalog, Apidra. Only patients free of diabetic complications were enrolled. The other criteria for inclusion were no personal history of other cardiovascular or metabolic diseases, no simultaneous participation in another clinical trial, being free of any acute infections up to one week prior to the study, and HbA1c < 7.5%.

The medical history and information about diabetes etiology of the study participants were prepared by medical personnel. The adolescents and their parents were presented with a comprehensive description of the aim and methods of the study. Written consents were requested and obtained from all parents. The study protocol was approved by the Ethics Committee of the Academy of Physical Education in Katowice, Poland, and conformed to the standards set by the Declaration of Helsinki.
