Introduction:
Phase II of cardiac rehabilitation includes 36 sessions of exercise developed over 12 weeks, an intervention format that seems to be based on historical practice and not on scientific evidence. The objective was to evaluate the effect of two types of exercise volumes on exercise capacity, physical activity levels, and quality of life in subjects undergoing percutaneous coronary intervention.

Methods:
A randomized controlled clinical trial was performed in 17 subjects, who were randomly assigned to two groups. The first (n = 7) was trained for eight consecutive weeks, and the second (n = 10) for 12 weeks. The six-minute walk test, the International Physical Activity Questionnaire, and the SF-36 were applied before starting the cardiac rehabilitation program at 8 and 12 weeks.

Results:
No significant differences were found between the intervention groups. The rise of VO₂max was only significant in the 8-week group. Both groups improved the distance walked and sedentary behaviour. The 12-week intervention group improved the quality of life, specifically in physical functioning, and the 8-week intervention group in the domains of social function, physical, and emotional role. Additionally, the percentage of participants meeting physical activity recommendations was higher in the 12-week cardiac rehabilitation group.

Conclusions:
The implication for the practice is that the exercise traditionally used in cardiac rehabilitation shows early changes in exercise capacity and quality of life. The results of the levels of physical activity and sedentary behaviour improved after 12 weeks of rehabilitation without the presence of adverse events.