When your heart beats, it squeezes blood from inside its chambers to the large arteries. This sudden bolus of blood causes normal arteries to expand like balloons do when they fill with air. The walls of arteries have sensors that allow arteries to expand with each pulse of blood. If the arteries do not expand enough when blood enters them, blood pressure can rise very high. Blood pressure is determined by the force of the heart’s contraction times the resistance in the blood vessels. Normal blood pressure is 120 when the heart contracts and 80 when it relaxes. During exercise, the heart beats with increased force to raise blood pressure. It is normal for blood pressure to rise up to 200 over 80 during running, and to 300 over 200 while doing a leg press with very heavy weights.
People with normal resting blood pressures who develop very high blood pressure during exercise are the ones most likely to develop high blood pressure later on. If your blood pressure rises much above 200 during running, you are at increased risk for developing high blood pressure.
Ninety percent of Americans will develop high blood pressure, which increases risk for heart attacks, strokes, kidney damage and sudden death. High blood pressure usually occurs in people who have normal blood pressures when they were young. If you have an exaggerated blood pressure rise during exercise, you should go on a heart attack prevention program that includes a diet that is high in plants and low in saturated fats and refined carbohydrates, regular exercise, losing weight if you are overweight, not smoking, and avoiding stimulants and drugs that raise blood pressure.