Chronicles

It is well known that physical exercise is important for the preservation of a healthy lifestyle and mental well-being throughout life. During exercise practice, the tissues and organs of our body need more energy and oxygen than usual to function. For example, at resting, the skeletal muscles receive 20% of the total blood flow (containing oxygen and nutrients), but during exercise the demands increase, and this value goes over 80%! To compensate, our cardiovascular system, composed by the heart and blood vessels (arteries, veins, etc.), is stimulated by the central nervous system to increase its activity - the heart contracts and relaxes at a higher pace and more intensely, pumping blood through the blood vessels around the body with a bigger flow, an alteration that is accompanied by an increase in the activity of the respiratory system. Therefore, to allow for the practice of physical exercise, a sound state and function of the cardiovascular system is absolutely essential.

On the other hand, exercise practice contributes to the long-term and proper functioning of the cardiovascular system. This is partly due to the effect of exercise in calorie expenditure; an excess of calories can result in the accumulation of fat and an increase in blood cholesterol levels, which sometimes leads to obesity and the development of diabetes mellitus. These disorders increase the risk for cardiovascular diseases, the principal cause of mortality in developed countries and estimated to account for 17.3 million deaths a year. One of the most common cardiovascular diseases are myocardial infarctions - also known as “heart attacks”-, which in most cases are the result of the obstruction of a coronary artery. The coronary arteries are the blood vessels that supply blood to the heart muscle for it to function, and an accumulation of fat in these vessels (atherosclerosis), can block the flux of blood to the heart. This interruption in the bloodstream damages the heart muscle permanently, resulting in a diminished capacity of the heart to pump blood throughout the body. This reduction in the function of the cardiovascular system can also be manifest through an incapacity to provide the body with the quantity of nutrients and oxygen it needs, especially while practicing exercise (for example, these patients become short of breath with a lower level of physical effort than an average person). However, it is important to note that, in cases of serious cardiac deficit, these effects are apparent even during daily life activities, in the absence of exercise practice. Therefore, it is clear that not only the performance of exercise requires an efficient activity of the cardiovascular system (which can be affected in cases of cardiovascular diseases), but also that the practice of exercise helps preserve a lifelong good function of this system.

However, it is not only in disease states that the cardiovascular system suffers from disruptions that lead to a reduction of its function, these also occur naturally with aging. As we age, the heart suffers several changes: the cells of the heart muscle - the millions of minuscule alive components (10 times smaller than 1 millimeter) that synchronously contract and relax and together make the heart pump - start to lose its capacity to contract and relax; the extracellular matrix (the network of proteins, lipids and sugars that embeds and supports the heart cells) becomes more rigid, making it harder for the heart to relax; the mitochondria (the “energy generators” that exist within most cells) of the heart muscle cells become dysfunctional, which negatively affects the amount of energy available for the heart to pump blood; and in the end, with time, the heart muscle loses some of these contractile cells. Thence, as a general rule, old people also feel a certain intolerance to intense exercise practice due, amongst others, to a less efficient cardiovascular system. Similar to the relationship between cardiovascular diseases and exercise, studies show that regular physical activity can reduce, and even reverse, some of these alterations of the aging heart.

To sum up, physical exercise is intimately related to the cardiovascular system and it is important to practice exercise throughout our life. In the future, innovative strategies involving synthetic materials of nanometric dimensions (at least 1 million times smaller than a millimeter!) and stem cells (cells that can replicate and differentiate in different cell types, including heart muscle cells) - already under investigation by scientists, even here in Portugal - will contribute to repair and regenerate the cardiac muscle in cases of heart failure, which will, for example, accelerate the recovery periods of patients, allowing for an active and healthy lifestyle for the rest of their lives.

Author: Lino Ferreira is a Principal Investigator and Luís Monteiro is a PhD student, both at the Center for Neuroscience and Cell Biology (CNC), University of Coimbra (UC), in Portugal.

The project: This chronicle results from the collaboration between the Center for Neuroscience and Cell Biology (CNC) of the University of Coimbra, the European Advanced Training Network FOIE GRAS (http://www.projectfoiegras.eu), the Erasmus+ Program and the Academic Sports Federation University (FADU) in the scope of the European University Games Coimbra 2018.

Coordination: Anabela Marisa Azul, João Ramalho-Santos, Mireia Alemany i Pagès, Paulo Oliveira and Sara Varela Amaral

Illustration: Rui Tavares