## 2 Topics and Results
### Blood Volume  
The change in blood volume in the body is an important adaptation process [81], occurring as a result of the impact of various factors: physical exercise, external stressful influences (thermal acclimatization and thermoregulation), injuries and diseases [82]. An increase in blood volume (hypervolemia) has been demonstrated after systematic training and physical endurance exercises [81]. Whole blood volume is the sum of the volume of erythrocytes (because they are the most numerous cells in the blood) and the volume of blood plasma. The volumes of the other types of blood cells are negligibly small. Both the erythrocyte and blood plasma volumes can change independently of each other and thereby change the total blood volume [82]. [PERSON] et al. (1999) [83] show the dependence of the three volumes (whole blood, blood plasma and erythrocytes) on body mass, specifying that the individual is not overweight. The data refer to young, non-obese men and were obtained on the basis of radioisotope examination (51 Cr and 125I scan of erythrocytes and albumin). Since vascular volumes are also directly related to body weight, their reference levels are expressed per unit of body mass (L/kg). The reference values for the three vascular volumes (blood, plasma, erythrocytes) are respectively--whole blood 63-82 mL/kg; plasma volume 38-49 mL/kg and erythrocyte volume 24-33 mL/kg [83; 84; 85]. Normally, the increase in erythrocyte volume occurs slowly (over several weeks to months, regular physical exertion), whereas the increase in plasma volume can occur rapidly (within hours or days) [83]. An increase in plasma volume, as a component of blood volume, is reported in almost all cases of induced hypervolemia as a result of exercise training (lasting up to 2-4 weeks). After this period, the increase in blood volume can be distributed equally between plasma and red blood cell volumes. Exercise as a stimulus for hypervolemia has a thermal and non-thermal component that increases total circulating plasma levels of electrolytes and proteins [81]. Although the movement of proteins and fluids from the extravascular to the intravascular space may be considered a mechanism for rapid hypervolemia (occurring immediately after exercise), there is also evidence to support the thesis that chronic hypervolemia represents an increase in total body water and soluble substances in the body. The increase in body fluids during exercise training is associated with increased water intake and a decrease in the volume of urine output. Hypervolemia provides increased amounts of body fluids in the body to \"dissipate\" heat and hence for increased thermoregulatory stability. Hypervolemia contributes to greater vascular volume and cardiac filling pressure, increased systolic cardiac output, and hence improved heart rate during exercise [81]. A review article is available in the scientific literature [81] which tabulates the specific percentage increase in blood volume, plasma volume and mean erythrocyte volume with gradually increasing training duration in days, with different load regimes at different active muscle groups. [PERSON]'s (1991) comparative analysis [81] included 15 different author groups and their results. It is important to note that the percentage change of the three parameters--erythrocyte volume, plasma volume and whole blood volume is different in absolute value, starts at different times, but settles to a constant level after a different time interval for all three volumes. It should also be added that even doing just one workout can contribute to an increase in overall blood volume. The observed hypervolemia in the aforementioned scientific paper shows a \"plateau\" in the increase in blood volume after about a week of intense exercise. The reported increase in blood volume after about 10 days of training may be mainly due to increased plasma volume, with an almost minimal increase in mean erythrocyte volume.