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The aim of our study was to determine changes in some biochemical indices (alanine (ALT) and aspartate aminotransferase (AST), lactate dehydrogenase (LDH)) as well as lactate and pyruvate level in the blood of horses exercised in recreational horseback riding from Pomeranian regions during a training session. Measurement of values of liver biomarkers (AST, ALT) and muscle damage indicator (LDH), followed by a variety of training programs, can help to better understand the acute and chronic effects of resistance training. Thirteen healthy adult horses from central Pomeranian region in Poland (village Strzelinko, N54°30'48.0" E16°57'44.9"), aged 9.5±2.4 years old, were used in this study. All horses participated in recreational horseback riding. Training started at 10.00 AM, lasted 1 hour and consisted from a ride of cross country by walking (5 min), trotting (15 min), walking (10 min), trotting (10 min), walking (5 min), galloping (5 min), and walking (10 min). Blood was drawn from jugular veins of the animals in the morning, 90 minutes after feeding, while the horses were in the stables (between 8.30 and 10.00 AM), and immediately after exercise session (between 11.00 AM and 2.00 PM). Blood was stored in tubes with K3-EDTA and sodium citrate (3.8%) and held on ice until centrifugation at 3,000 rpm for 15 minutes. The plasma was removed. Plasma was used for the determination of aminotransferases and lactate dehydrogenase activity; whole blood was used for determination of lactate and pyruvate level. The regular training lead to adaptive processes which provoke changes in biochemical indices. In our research, non-significant alterations of AST and LDH activities in horses involved in recreational horseback riding were observed. This may indicate a normal course of aerobic-anaerobic glycolysis in horses involved in recreational horseback riding during a training session. Moreover, ALT activity was decreased by 20.6% (p = 0.000) during a training session. Increased blood lactate level in horses involved in recreational horseback riding during training session could be explained by increasing lactate formation via the reduction of pyruvate catalyzed by LDH as a result of anaerobic energy supply. Based on these results, it is concluded that the endurance exercises lead to specific metabolic changes accompanied by a redistribution of energy supply for improving resistance to exercises and athletic performance of horses. Therefore, the present data can be useful to assess the status of athletes and the degree of their training adaptability providing an opportunity to modify the training schedule to achieve the desired performance.