Chronicles

As we age, we progressively lose mobility. We need more effort to move our joints and the movements that we are able to perform are less wide. With age, some people actually feel pain when moving one or more body joints, a sensation that can be quite intense. Additionally, these joints become stiff, the amplitude of body movements is further reduced and painful deformities, for instance the so-called “bone spurs”, can develop. These processes are no longer considered part of normal aging, to which we are all subject, but represent an accentuated and accelerated destruction of articular tissues that characterize a disease called osteoarthritis.

It is natural to assume that a joint that already hurts, will hurt even more when moving, but that is not necessarily the case. In fact, in recent years, the benefits of physical activity on joint diseases have been clearly demonstrated. Physical activity increases general well-being, improves the joint mobility and reduces pain, and therefore, exercise is now part of patient-centered integrated therapeutic interventions recommended for the treatment of people with arthritis.

The articular cartilage, that is, the tissue that covers the bone extremities, does not contain blood vessels, and therefore, the cells of these areas get their nutrients from the liquid that lubricates the articular surfaces which, in turn, is formed from the blood that circulates in the surrounding tissues and also probably from the subjacent bone. This process is greatly facilitated by articular movement, that is, the succession of compressions and decompressions of the articular cartilage, which allows for the elimination of waste products resulting from cellular activity that would otherwise accumulate in the cartilage and have a potential toxic effect on its cells, the chondrocytes. At the same time, articular movement allows for the joint to receive an influx of water, nutrients, oxygen and other compounds such as hormones and vitamins that are important for the activity of these cells. Altogether, these processes ensure an appropriate nutrition of the chondrocytes and the regulation of their activity according to the needs of the joint. We can assume then, that without movement, the survival of the chondrocytes is compromised and this in turn, threatens the integrity of the cartilage.

Hence, a sedentary lifestyle does not only increase the likelihood of developing joint diseases like osteoarthritis, but it also implies that cartilage that is already affected will have a diminished capacity of survival and regeneration, which will further aggravate the disease. On the other hand, it is known that the chondrocytes are highly sensitive to mechanical stimulation, managing to detect forces of a wide range of intensities and frequencies. These forces can have diametrically opposed effects in the activity of these cells. While forces of moderate intensity and frequency stimulate the formation of new cartilage, both immobility and violent movements have the opposite effect, stimulating the processes that destroy the cartilage and other articular tissues. That is why, it is important that exercise is tailored to each patient. Besides the beneficial effects of exercise on chondrocytes, the increase in muscle strength resulting from exercise practice is also fundamental because it contributes to stabilize the joints, such as the knee, the hip and the spine, enhancing posture and balance, and therefore, mobility. Osteoarthrosis is also associated to other diseases, especially metabolic diseases such as diabetes and obesity, that increase articular destruction. It is well known that a good control of our metabolism has many beneficial effects at the articular level, reducing significantly joint deterioration as well as the manifestation and progression of osteoarthritis symptoms, for instance articular pain and loss of mobility. Since exercise practice is highly beneficial for both obesity and diabetes, especially type 2, these positive beneficial effects also extend to the joints.

To sum up, either through direct effects on the articular tissues, or through the beneficial effects on other diseases that further aggravate the condition of osteoarthritis, adequate and tailored exercise practice significantly contributes to the preservation of articular health - mitigating pain and improving mobility - and to the promotion of a better quality of life and a healthy and active aging.

Author: Alexandrina Ferreira Mendes is a Researchers at the Center for Neuroscience and Cell Biology (CNC), University of Coimbra (UC), in Portugal and Professor at the Faculty of Pharmacy of the University of Coimbra (FFUC).

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