The goal of this clinical trial is to find out whether partly replacing aerobic interval training (AIT) with resistance training (RT) leads to greater improvements in physical fitness and muscle mass in women with coronary artery disease (CAD) during cardiac rehabilitation.

The main questions this study aims to answer are:

• Does combining RT (squats and pulling exercises with weights) with a reduced amount of AIT (cycling) improve aerobic fitness in the same way as AIT alone?
• Does the combined training lead to greater improvements in muscle mass compared with AIT alone?
• Does slow-speed RT (slower lowering phase) result in lower heart rate and blood pressure during exercise compared with normal-speed RT?

Researchers will compare three exercise programs:

• AIT only (control group),
• AIT combined with normal-speed RT (1-second lifting, 2-second lowering),
• AIT combined with slow-speed RT (1-second lifting, 5-second lowering).

Participants will take part in a 12-week cardiac rehabilitation program and will train three times per week.

At the start and end of the program, participants will complete a cycling fitness test, body composition assessment, blood sampling, two strength tests, and quality-of-life questionnaire.

CAD remains one of the leading causes of death among women worldwide. Although cardiac rehabilitation programs with AIT are well established, the optimal way to include RT in this population remains unclear. Historically, RT was limited in patients with heart disease due to concerns about excessive blood pressure responses and cardiovascular risk. However, recent evidence shows that properly prescribed RT is safe and may significantly improves muscle strength, aerobic fiitness, and overall quality of life.

The study consists of two sequential phases. The first is a crossover feasibility phase designed to compare the acute hemodynamic responses (blood pressure, heart rate) and rate of perceived exertion between two RT protocols: (1) traditional high-load RT (1-second lift, 2-second descent) and (2) high-load RT with a prolonged eccentric phase (1-second lift, 5-second descent). The goal of this phase is to confirm the feasibility and short-term safety of both approaches before inclusion in the main trial.

The second phase is a three-arm, parallel-group randomized controlled trial. After baseline assessments, participants are randomized into one of three groups using block randomization with variable block sizes to ensure balanced allocation throughout recruitment.

The 12-week intervention includes three supervised sessions per week, totaling 36 visits. AIT follows a structured progression based on heart rate reserve, alternating between high- and low-intensity cycling intervals on a stationary ergometer. RT sessions consist of compound lower-body and upper-body movements (hex-bar squat and horizontal cable pull), performed at approximately 80% of one-repetition maximum. Training intensity, load progression, and repetition tempo are standardized across groups, ensuring equivalent time under tension per set.

To maintain participant safety, all exercise sessions are supervised by medical and rehabilitation staff, including a physiotherapist, nurse, and kinesiologist, with a cardiologist on call. Continuous heart rate monitoring and pre- and post-exercise blood pressure measurements are performed during each session. Any adverse events will be recorded and reviewed by the study physician.

Statistical analyses will follow the intention-to-treat principle.

Inclusion Criteria:

• documented CAD,
• stable clinical status (at least 1 month since myocardial infarction and/or elective percutaneous coronary intervention, at least 3 months since cardiac surgery).

Exclusion Criteria:

• based on the American Heart Association guidelines for resistance training in patients with CAD,
• pregnancy.