Physical activity in the form of exercise and training preserves and improves functional physical abilities and is an important factor in prevention, treatment and rehabilitation of many diseases. As well as for people, the way in which exercises are performed, the intensity, the physical condition, good shape and nutrition are very important for dogs too. All these factors if not properly used can cause disturbances in the body during exercise. Aerobic activity includes the increase in the number of erythrocytes, increases blood flow, myoglobin content and mitochondria in muscle cells, as well as an increase in enzymatic activity of aerobic glycolysis which then enables the creation of ATP necessary for muscular function and facilitates the delivery of oxygen to the tissues. In this study hematological parameters (the number of erythrocytes, hemoglobin concentration, hematocrit, MVC, MCHC, the number of leukocytes) and biochemical parameters (ALP, AST, ALT, CPK, glucose, BUN) were measured in the blood of 18 dogs that were running on a treadmill for 20 minutes three times a week in the period of four months. The blood samples were taken in the beginning and in the end of the four-month study. The results indicated a statistically significant increase in two biochemical parameters, namely the alkaline phosphatase (ALP) and aspartate aminotransferase (AST). However, the increased values were still within the reference range. The very increase of these enzymes may be due to the rapid metabolism caused by stronger physical activity and stronger muscular activity.