Abstract    The sport efficiency of horse depends on its ability to overcome excess metabolic requirements during severe physical activity. One of the methods to evaluate these metabolic requirements is determination of the kind and rate of changes preduced in biochemical parameters. In the present study that was done in nine Arab horses from 4 to 10 years old, serum concentration of calcium, phosphorus, sodium, chloride and potassium were measured in different times before and after intensive physical activity. The blood samples were collected at 1 h before (T0) just after )T1(, 3 hours (T2) and 24 hours (T3) after running with maximum speed in a 1250-meter course.The results showed that except for calcium and chloride, the other minerals were significantly increased just after running or in other times compared to (p