Still, the possible connections between hemorheology and longterm aerobic physical training in a relatively large ischemic heart disease population have not been investigated previously. A systematic literature search in PubMed with the keywords hemorheology, physical activity, physical exercise, cardiovascular diseases and atherosclerosis, identified only 14 nonrandomized controlled studies from the past 25 years in which original data were used to determine changes in hemorheological parameters, mostly in healthy volunteers and athletes, but also partially in patients with CV diseases, participating in short-term exercise training. Investigations involving healthy volunteers have proven that short-term physical activity has acute effects on the hemorheological parameters, including increases in Hct and WBV due to the fluid shift, water loss and release of sequestered red blood cells from the spleen. In contrast, long-term training causes autohemodilution, resulting in reduction of PV and WBV. On the other hand, the findings of red blood cell aggregation and deformability studies are not concordant. Some investigations dealing with long-term physical activity performed by healthy volunteers, suggested the deterioration of rheological factors, whereas others reached the opposite conclusion. These discrepancies might be explained by differences in training periods, study designs, methods, the selected populations and the exercise performed. Only few studies have focused on the effects of exercise on hemorheological factors in CV patients. Several investigations have shown that acute training evokes increases in PV and fibrinogen. Levine et al. were unable to demonstrate any hemorheological effects after a 10-week CR training, but Church et al. reported reductions in WBV and PV after a 12-week CR program. In our present study, we investigated whether we could demonstrate any hemorheological changes in ischemic heart disease patients participating in a 24-week ambulatory CR training program. The results pointed to a slight Reversine decrease in Hct, while significant decreases were observed in WBV and PV, resulting in a significantly increased Hct/WBV ratio. The red blood cell aggregation indices and the measured deformability parameters were also significantly enhanced at the end of the training program. Although the blood flow of the coronary vessel system is primarily determined by hemodynamic factors, under certain conditions the role of rheological parameters becomes important. The observed beneficial changes in the macrorheological parameters presented in this investigation presumably reduce the CV risk of ischemic heart disease patients. In addition to the positive findings among macrorheological parameters, microrheological changes could also have a pivotal role in the development of better physical fitness. The diameter of the narrowest capillaries in the body, found in the myocardium is the importance.