EN
Blood from horses was examined during races at rest just before and 30 min after an effort. The horses started at steeplechase in which a distance of 3000 m with 16 handicaps they should cover at a speed of 520 m/min. The level of haemoglobin, hematocrit, blood sedimentation after 15 min. content of lactic and pyruvic acids, glucose, total protein and inorganic P were determined. Basing on the values determined at rest and on changes of the examined parameters after an effort, horses were divided into two groups: well trained and unprepared for races. In the last group was found a low content of haemoglobin and low value of hematocrit at rest, high value of blood sedimentation delayed removal of lactic acid from blood. The content of pyruvic acid at restitution increased causing an additional acidosis.