Erythrocytic system under the influence of physical exercise and training.

It is obvious that physical performance, endurance capacity and resistance to fatigue in humans are dependent upon many different factors. One factor, the oxygen carrying capacity of blood, seems to be of particular importance. This factor is mainly determined by haemoglobin concentration, number of circulating erythrocytes and the efficiency of their functions. A single bout of physical effort and, even more, repeated exercise may change the morphological indices of blood and influence the erythropoietic processes in the bone marrow. That is why there is so great an interest now attached to the effects of physical exercise on the erythrocytic system. Although in recent years many papers have been published on the subjects their findings pertaining to the effects of single bouts of exercise and systematic training on the erythrocytic system are often contradictory. The haematological parameters in some top-class athletes, particularly those performing in endurance disciplines are lowered at rest. Anaemia has been described in sportsmen, even among the members of Olympic teams. This type of anaemia has been called 'sports anaemia', 'athletes' anaemia' or 'postexercise anaemia' in order to emphasise its character. Among many possible causes which may bring about the development of sports anaemia the most commonly recognised are: postexercise plasma expansion, intensified haemolysis during physical efforts, iron deficiency, losses of erythrocytes by the way of bleeding into the digestive and urinary systems and also some disturbances in erythropoiesis. However, there is evidence of the intensification of erythropoiesis by many factors occurring during physical exercise.