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. These people have arteries that do not expand as much as normal arteries when blood is pumped to them. When your heart beats, it squeezes blood from inside its chambers to the large arteries. This causes normal arteries to expand like balloons. If the arteries do not expand enough when blood enters them, blood pressure can rise very high.
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. If your blood pressure rises much above 200 during running, you are at increased risk for developing high blood pressure. You should go on a heart attack prevention program that includes a diet 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. Check with your doctor.