The heart is a hollow muscle comparable to a pump that sucks the blood that circulates through the veins and pushes it towards the arteries; It changes its size throughout the life of the person, being larger in men than in women. Its size increases with exercise like any other muscle. In one day the heart moves 100,000 times, and in that same period 8,000 liters of blood circulate inside it. Our body has 125,000 kilometers of blood vessels; If we placed them in a straight line they would go around the world 3 times. The blood vessels divide and supply blood throughout the body, the smallest being the capillaries (these are very narrow), and oxygen and nutrients filter through their thin walls into the cells. Oxygen-poor blood returns to the heart through the veins. IMPORTANCE OF HEART RATE VARIABILITY Heart rate variability or coherence is the variation in time between two successive beats. Contrary to what most people think, it is important that the heart does not beat regularly and that the interval between beats varies. A healthy heart will beat faster during inspiration than during expiration (this means that there is a balance in our autonomic nervous system – the one that is automatic, involuntary). French psychiatrist David Servan, in his book Emotional Healing, describes the importance of good heart rate variability, stating that people suffering from depression or stress, without exception, have low heart rate variability. In the next post we will develop this topic in more depth and we will see an exercise to improve this situation.