Cardiac rehabilitation: endurance, strength or interval training?

I have already posted the KNGF's guidelines for cardiac rehabilitation. What is interesting to note here is the type of exercise that is recommended by these guidelines.

Let's remember first how this guideline defines cardiac rehabilitation:

"These KNGF clinical guidelines have been devised for the implementation of physical therapy in patients who have had an (acute) myocardial infarction, or who have undergone a coronary artery bypass operation, percutaneous transluminal coronary angioplasty, a heart valve operation, or operative correction of a congenital heart disorder".

Cardiac rehabilitation involves a wide range of activities, such as practicing basic skills and daily life activities,  and sports training. Therapy can take the form of fitness or aerobics exercises, swimming, or exercises in  water. The therapeutic approach chosen must provide the most appropriate and specific way of increasing the patient’s daily activities. If therapy is focused on physical training, use of an ergometer and sports training are involved. ECG and blood pressure monitoring are carried out if indicated by the rehabilitation team.

Examples of training variables are the intensity, frequency and duration of training, and the length of the rest intervals. However, training structure is also important. General indications of training variable values are:

1. Practicing specific functions, skills and activities while encouraging the patient to enjoy exercise: training frequency should be 2–3 times a week.

2. Aerobic exercise: training intensity should be at 40–85% of maximum oxygen uptake and at 11–16 on the Borg scale; training should consist of a warm-up period, aerobic training, and a cooling down period, and should last 20–60 minutes; training frequency should be 3–7 days a week.

Effects of aerobic training on the cardiorespiratory system. Source: Jongert et al.(52)

• lowers heart rate;

• increases heart pump output volume;

• increases heart minute volume during maximum-intensity exercise;

• increases blood volume and hemoglobin level;

• increases artery-vein oxygen differential;

• lowers blood pressure;

• increases VO2-max;

• increases anaerobic threshold;

• increases maximum respiratory minute volume;

• increases ventilation;

• increases lung diffusion capacity;

• increases lung volume and capacity.

3. Strength and aerobic exercise: training intensity should be at 40–50% of maximum strength; each training session should comprise 1–3 sequences of 10–15 repetitions with pauses lasting 1–2 minutes; resistance should increase with time, both relatively and absolutely; training frequency should be 2–3 times a week. Circuit training should last for 20–30 minutes and should consist of a warm-up period, strength training, and a cooling-down period.

Effects of strength training on skeletal muscle. Source : Jongert et al.(52)

• functional hypertrophy;

• increased mitochondrial numbers (mitochondrial hypertrophy);

• increased capillary circulation;

• increase in muscle enzymes;

• increased energy-rich phosphate level.

4. Reduction of risk factors: exercises that have a longer duration, lower intensity and higher frequency are recommended for patients with obesity, hypertension, diabetes mellitus (type-II), and lipid disorders.

Individual exercise programs are devised using the results of tests of maximum symptom-limited aerobic capacity.