The increase in the prevalence of cardiovascular diseases (CVD), directly associated with the aging of the population, is a concern for public health in Portugal. Given the high prevalence of risk factors and the increasing number of cases of CD throughout Alentejo, where there is no cardiac rehabilitation (CR) coverage, there is an urgent need for the implementation of a CR program.

CR has evolved over the past decades to multidisciplinary approaches focused on education, individualized training, modification of risk factors, and overall well-being of cardiac patients. Studies suggest that high intensity interval training (HIIT) allows greater patient benefits compared to moderate continuous training (MCT), reversal of DC and increased aerobic capacity in CR patients. This study intends to compare HIIT and MCT interventions investigating direct and indirect associations between informally performed physical activity (AF), sedentary behavior, cardiovascular fitness and quality of life (QoL) among patients enrolled in RC programs in phase III.

According to WHO (1) cardiovascular diseases (CVD) are the number 1 cause of death globally: an estimated 17.5 million people died from CVD in 2012, representing 31% of all global deaths. In 2013 there were 1.9 million deaths resulting from CVD of the circulatory system in the EU-28, which was correspondent to 37.5 % of all deaths considerably higher than the second most prevalent cause of death, cancer.

In Portugal, cardiovascular diseases lead to morbidity and mortality rates, which makes evident the importance in the Public Health scenario and the need to implement measures aimed at primary and secondary prevention. In 2004, cardiovascular diseases signify 39% of all causes of death, since then a reduction in these values has been recorded and, according to more recent data (2013), the values are around 29.5%.

As these pathologies are associated, among other causes, with aging, the Alentejo emerges as one of the regions where the prevalence of these pathologies is greater. In fact, since Alentejo is the oldest region, it becomes an authentic Living Lab. In this way, this study intends to study the effects of different types of cardiac rehabilitation (CR) programs, emphasizing in particular the use of a high intensity interval program that we will compare with a traditional program.

For the program will be recruited patients who have been admitted in the Cardiology Services at Espírito Santo Hospital in Évora. Participants of both sexes will be included, between 18 and 80 years of age, meeting the criteria for low or moderate risk, class B for participation and exercise supervision, absence of signs/symptoms after cardiac surgery, with a left ventricular ejection fraction greater than 40%, according to the American Heart Association and the American Association of Cardiovascular and Pulmonary Rehabilitation.

Those who meet the inclusion criteria will be evaluated in a clinical context in order to determine the capacity to integrate phase III of CR. This phase will last about 6 weeks, will be held at the Nursing School located at the Espírito Santo Hospital.

The sessions will be supervised and will take place on a cycloergometer and treadmill, 3 times a week for 6 consecutive weeks. If a session is lost, it will be recovered that week or the following week. Each session will be limited to three participants.

The HIIT protocol will consist of four four-minute intervals at high intensity, stimulating 85-95% of peak-FC followed by active recovery at 70% peak-FC for a total of 20 minutes. The MCT protocol consists of continuously exerting moderate intensity, causing a peak-FC 70-75% for 27.5 minutes to equal the energy expenditure of the HIIT protocol. Both protocols will include a warm-up of 10 minutes at low moderate intensity (50-70% of peak-FC) and a 3 to 5 minute calm return period was performed at 50% of peak-FC.

During the intervention, the workload, FC and the subjective effort perception scale (EPE - Borg) will be recorded throughout each session, every minute for the HIIT training and all other minutes for the MTC. During the intervention the load will be adjusted to obtain the target FC.

After the exercise session, participants will complete 1 of 18 items of the Physical Activity and Pleasure Scale (PACES) on a weekly basis in which subjects rate their appreciation for the exercise of that week on a seven-point scale.

In the same period, the usual medical recommendations for cardiac rehabilitation through exercise will be provided to the Control Groups (phase III).

When subjects complete phase III CR, they will be given guidelines on exercise and nutrition. The intention is that participants after the program have adopted a healthy lifestyle, where the practice of physical exercise is a reality. The intention is also to verify if participation in one of the different exercise programs that have been implemented, in phase III of CR, can possibly provide better results both in maintaining good life habits and also in reducing the time in the sedentary activities, the "Active Couch Potato" phenomenon. More than solving a health problem at a certain stage of a subject's life, it is intended to consolidate healthy habits of life.

In order to verify which type of program allows to modify the habits of life towards the increase of the practice of physical activity, as well as the maintenance of these habits, we will carry out a follow-up at 6 months and one year after the beginning of the intervention.

Inclusion Criteria:

• low-moderate risk for physical exercise, with the following pathologies / conditions:
• stable coronary disease;
• after acute myocardial infarction;
• after coronary angioplasty;
• after cardiac surgery (coronary revascularization or valve surgery);
• stable chronic heart failure in class I-II of the New York Heart Association;
• acceptance of the informed consent assumptions of CR programs;
• must not have participated in physical exercise programs in the 3 months preceding the referral;
• should not have more than one hour of vigorous physical activity per week according to the International Physical Activity Questionnaire.

Exclusion Criteria:

• presenting symptoms of heart failure of class III and IV according to the New York Heart Association (or documented signs and symptoms of chronic heart failure with ejection fraction >45%);
• uncontrolled arrhythmias;
• severe chronic obstructive pulmonary disease;
• uncontrolled hypertension;
• symptomatic peripheral arterial disease; unstable angina;
• uncontrolled diabetes;
• inability to perform a maximum VO2 test;
• locomotion exclusively dependent on mechanical means.