Author(s): Felipp da Silveira Ferreira, Marcelo Borges dos Santos Junior, Rafael Viana Barbosa de Almeida Guerra, Paulo Moreira Bogossian, Sebastian Ricardo Bustamante Bustamante, Jéssica Martins Linhares, Claudio Baptista de CarvalhoFifteen conditioned Mangalarga machador and Arabian purebred horses were used to verify continuous electrocardiography (Holter) variables, through different endurance tests. Animals were divided into three groups of five animals: G1, 4km endurance`s test with an average speed of 15km/h; G2, 8km endurance`s test with an average speed of 12km/h; G3, 20km endurance`s test and an average speed of 12km/h. Holter was implanted as standardized in previous studies. Samples were taken before the test (T0), half of the competition route (T1), at the end of the test (T2), beginning of the rest period (T3) and every five minutes throughout the resting time (T4, T5 and T6), which lasted 15 minutes. Data were considered significant if p<0.005. Results showed sinus tachycardia during physical activity and distances of 4km at 12 or 15km/h, as well as distances of 8km and 20km at 12km/h did not produce heart rate changes. In conclusion, the proposed activities were well tolerated in terms of heart rate and frequency in conditioned horses.