How is the heart of a trained person different from the heart of an untrained person?

A trained person’s heart works more steadily under heavy loads or sports. This is achieved through periodic exercise and sports, when the heart is essentially “getting used”. In a person who does not play sports, the heart begins to beat violently under heavy loads. This is fine. But if the rhythm of the heart goes astray, then it is very dangerous for health and life, as it can cause a heart attack. Therefore, it is undesirable to engage in sports that load the work of the heart without special training.