Comparing Moderate and High-intensity Interval Training Protocols on Biomarkers in Type 2 Diabetes Patients

To overcome the lack of knowledge regarding the relative role of different intensities of aerobic training in adults with type 2 (T2D) diabetes, a 12 month randomized controlled trial will be performed to assess and compare the impact of two exercise groups: 1- high intensity interval training (HIIT) with resistance training; 2- moderate continuous training (MCT) with resistance training; and 3- a standard counseling home based control group; on hemoglobin A1c (HbA1c) as the main outcome, and other selected cardiometabolic, body composition and quality of life markers, as secondary outcomes. This investigation aims to increase the current knowledge on HIIT and the related benefits on diabetes control and treatment in a time saving and physiological efficient framework, which will improve the general health and well-being of the diabetes population. A total of 105 participants with T2D will be recruited from the Lisbon area (35 control, 35 HIIT, and 35 MCT). The investigators hypothesize that high-intensity interval training, compared to moderate continuous training, will optimize the physiological adaptations and quality of life in people with type 2 diabetes.

Contemporary exercise guidelines focus on continuous aerobic exercise using mainly moderate intensity exercises. However, there is growing evidence that HIIT has the same (or even further) benefits, with lower time commitment. This type of exercise has already been tested in T2D patients, using mostly short intervention studies, with significant improvements in relevant outcomes for T2D, such as glucose regulation. On the other hand, no study as yet compared the effects of HIIT and MCT (both combining resistance training, RT) in a long-term study design. Therefore, this study will use a 12 month randomized control trial to assess the effects of an HIIT combined with RT, and MCT combined with RT, in comparison with a control group (home base program), on glycemic control, inflammatory profile, endothelium function, cardiorespiratory fitness, quality of life, and body composition outcomes, in adult males and females with T2D.

The sample recruitment is planned to be made using media, mails, and community events. Participants can be considered eligible if age is set between 30 and 75 years old, a body mass index lower than 48 kg/m2, and if they have been diagnosed with T2D (according to the ADA criteria). Further criteria will be made upon their medical history concerning strokes, advanced neuropathy or retinopathy, and other health conditions that may interfere with this study's protocols or otherwise safe exercising. Power and sample size calculations (G-Power, Version 3.1.3) are based on a predicted hemoglobinA1c difference of 0.66 hemoglobinA1c units with an SD of effect of 1.2 hemoglobinA1c units, α=0.05, 1-β=0.80 and an expected dropout rate of 10%. The calculations yielded a minimum sample size of 105 participants (35 in each group).

The statistical analysis will be performed using SPSS Statistics (version 22.0, SPSS Inc., an IBM Company, Chicago IL, USA). Baseline differences between the interventions and the control group will be examined using ANOVA, or a non-parametric alternative in case of a non-normalized distribution. Outcome variables will be analyzed using three-way mixed factorial ANOVA. Intention-to-treat analysis will be performed. Simple and multiple regression analysis will be performed to test the relationships among the selected variables. Statistical significance will be set at p\<0.05.

Eligibility Criteria:
Inclusion Criteria:

* Men and women diagnosed with type 2 diabetes
* 30-75 years of age
* BMI \< 48 kg/m2

Exclusion Criteria:

* Documented cardiovascular disease
* Advanced neuropathy or retinopathy
* Physical health condition that may interfere with study's protocols or exercising safety