Effect of exercise on systemic blood pressure and heart rate in horses

Carotid loops were prepared in 3 horses several months prior to the experiments. Systemic blood pressure was recorded at rest and during exercise by insertion of a plastic cannula into the carotid artery. The pressure transducer was fixed at the neck of the animal. The blood pressure signal was transmitted by telemetry. When the horses were standing under the rider, the following results were obtained: heart rate 38 +/- 5 beats-min-1, systolic pressure 115 +/- 15, disstolic pressure 83 +/- 10, mean pressure 97 +/- 12, and pulse pressure 32 +/- 9 mm Hg. During steady gallop at a mean speed of 548 +/- 90 m-min-1, heart rate rose to 184 +/- 23 beats-min-1, systolic pressure to 205 +/- 23, diastolic pressure to 116 +/- 12, mean pressure to 160 +/- 20 and pulse pressure to 89 +/- 19 mm Hg. These values remained stable throughout the exercise period of 5-6 min. When the horses were exercised at stepwise increasing speed from walk through trot to gallop, both the mean arterial blood pressure and the pulse pressure rose in proportion to the running speed.