## Why the heart is more important than the muscles The heart is the main muscle in the body and supplies all organs with oxygen through the cardiovascular system. This is why an untrained heart will experience quick fatigue and the person will sweat heavily after even a little bit of physical activity. The main characteristic of the pumping function of the heart is the ejection fraction, i.e. the percentage of blood that the heart pushes out of itself per contraction (of the total volume of blood in the heart). The normal value is 55 % or more. For the heart to contract well, it needs a lot of oxygen. To do this, blood flow in the coronary arteries — the arteries of the heart — must be operating optimally under all conditions. If an area is deficient in oxygen, the vessels there "collapse," and blood is redirected to areas with good oxygenation. Like other muscles, heart cells can be trained to work under conditions of lower oxygen saturation. For example, the average amount of oxygen in the blood decreases during high physical exertion. Regular training allows the cells to "learn" to contract in less than ideal conditions. However, it's a long process. Abrupt jumps in exercise risk a heart attack. You shouldn't expect that two months of intense training will prepare you for a marathon — it takes much longer to train the heart for prolonged physical activity. ## What is the goal? In your cardio training, aim to get your heart pumping more than 55 % of blood in a single contraction. This can be achieved if ===the heart rate is maintained at 110–140 (or better, 120–130) beats per minute during physical activity. If the heart is forced to contract more frequently, it can seriously undermine health. ## Train the heart correctly Good exercises for heart health include: - Running - Brisk walking - Swimming - Jumping rope - Aerobics - Cycling and elliptical trainers Be sure to monitor your pulse rate, which should be approximately 120–130 beats per minute during physical exertion. While exercising, take periodic 30-second breaks. A heart rate that is too low means the exercise is not stimulating enough, and a heart rate that is too high means the person could be in danger if they don’t reduce the level of exertion. The heart rate is measured several times per session. In contrast to strength training, which involves a much higher load on the muscles, the effect of cardio training is achieved by performing a large number of repetitions of a single exercise. With smaller loads, a person's heart and lungs work better and the metabolism speeds up. Training should be done regularly — ideally 3–4 times a week. Keep in mind that you should also monitor your diet and consult with your doctor before beginning cardio training.