**3.3.5 Physical activity**

Physical activity plays an important role in our life, since it is the cheapest way of strengthening our health and reduces the risk of developing cardiovascular diseases. It has been confirmed that physical activity decreases the concentrations of total plasma homocysteine and thus the probability of developing a cardiovascular disease in healthy and already sick people. In the study called Bed rest "The influence of simulated weightlessness upon the human organism" performed in 2006, 2007 and 2008 at the Valdoltra Orthopaedic Hospital, Slovenia, in which young male participants (age 24-30 years) rested in horizontal position for 35 days, a statistically increased homocysteine concentration was documented (Plazar et al., 2008). The diet composition and the energy intake were daily supervised and monitored by a dietician. Volunteers were non-smokers, non-alcoholics, without history of cardiovascular and neuromuscular disorders*.* Several studies indicate physical activity as an independent lifestyle factor connected with lower homocysteine concentration. Besides, exercise is associated with a reduction in plasma fibrinogen concentrations, and with increasing activity levels of exercise a reduction in homocysteine was observed. So, this prolonged bed rest study confirms that increased levels of homocysteine in blood, negatively influences the cardiovascular system. Although, the precise mechanism is not well understood, similar consequences can result from prolonged physical inactivity in everyday life.
