The purpose of this study is to investigate the effects of aerobic exercise on glucose tolerance in individuals with cystic fibrosis.

The hypothesis is that performing High Intensity Interval Training glucose tolerance will improve in individuals with cystic fibrosis.

This is a controlled, randomized, and single blind trial. The first researcher (P1) will be responsible for the randomization process; the second researcher (P2) will be responsible for the evaluations and reevaluations. This evaluator (P2) will be "blind", meaning that for him it is totally unknown in which group each patient will be insert; and the third researcher (P3), will be responsible for statistical analysis.

Individuals will be recruited at the Child and Adolescent Health Care Unit of the Onofre Lopes University Hospital (HUOL) and in the Department of Physical Therapy of the State University of Paraíba (UEPB), Campina Grande - PB, Brazil. They will be evaluated at the Physical Therapy Department of the Federal University of Rio Grande do Norte (UFRN), Natal - RN, Brazil and in the Department of Physical Therapy of the State University of Paraíba (UEPB), in the city of Campina Grande - PB. A pilot study will be carried out and the sample calculation will be done with the data collected to reach a statistical power of 80% and a level of significance of 0.05%. Allocation in the groups will be performed by P1, randomly in blocks by the volunteer being prepubertal or pubertal. The R Core Team software (2015) will be used for this process.

In this study two groups will be considered: control group (CG) and aerobic exercise group (AEG). The CG will be submitted to educational intervention. The AEG will be submitted to the same educational intervention and to the High Intensity Interval Training.

After the pilot study, the patients will be evaluated to obtain information on severity and exacerbation of the disease, quality of life, metabolic evaluation, anthropometric measures, and lung function. All evaluations will be carried out at the same day period (morning). Researcher two (P2) will be responsible for the evaluation and reassessment procedure of the individuals, hence he will be "blind" meaning that for him it is totally unknown in which group each patient will be or was inserted. Individuals will be instructed to do not perform physical activity in the day before the evaluations. After this step, individuals will be randomly distributed in CG or EAG.

Volunteers from both groups will be instructed to maintain nutritional, drug and secretion care. In addition, they will be instructed to do not get engaged in any other kind of physical activity. The intervention will last 2 months and will occur 3 times a week until a total of 24 sessions. After the intervention ends and after the 8-week follow-up, all volunteers will be reevaluated.

Inclusion Criteria:

• Diagnosis of cystic fibrosis, according to the Brazilian Guidelines for diagnosis and treatment of CF;
• Prepubertal or pubertal, according to the Tanner scale
• Both sex.

Exclusion Criteria:

• Inability to perform the protocol established to the study;
• To be unable to understand and / or perform procedures.
• Exacerbation of the clinical picture, defined as modification and / or addition of antibiotic.
• To be pregnant.

Simple blind (investigador/outcomes aseessor)