Blood pressure is one of the many things affected physiologically when you exercise. Blood pressure is the pressure made by the blood against the arterial walls during contraction and relaxation of the heart. When you perform aerobic or anaerobic exercise--such as strength training and sprinting--there are both acute changes that occur during exercise as well as long-term adaptations that occur as a response to exercise.
Blood pressure is expressed by two numbers: the systolic blood pressure and the diastolic blood pressure. The systolic blood pressure is the higher of the two numbers and represents the highest pressure against the arterial walls when the heart contracts and pushes the blood through the arteries. The diastolic blood pressure is the lower of the two numbers. Diastolic pressure is the lowest pressure in the artery, and occurs when the ventricle is filling and the heart is at rest.
Blood pressure does increase in direct proportion with the intensity of the exercise. Systolic blood pressure increases to meet the demands of the body during exercise, and can increase from 120 mmHG before exercise and exceed 200 mmHg during exercise and still be considered normal. Diastolic blood pressure changes little, if at all, during exercise. Since diastolic blood pressure is the pressure in the walls when the heart is at rest, it is not affected during exercise. In fact, a diastolic blood pressure increasing greater than 10 mmHg during or after exercise represents an unstable form of hypertension, and may be associated with coronary artery disease, notes Len Kravitz, Ph.D. of the University of New Mexico.
After exercising, your systolic blood pressure should progressively decline during active recovery such as low-intensity walking. During a passive recovery such as sitting or lying down, your systolic blood pressure may drop suddenly due to the pooling of blood in your hands and feet. Additionally, because the blood vessels have widened slightly during exercise to allow for greater blood flow, there may be a drop in diastolic blood pressure following exercise.
Regular endurance exercise can result in a decrease in resting blood pressure in individuals with borderline or moderate hypertension, and can also result in a decrease in blood pressure during submaximal exercise. Resistance training or lifting extremely heavy weight can often cause your blood pressure to increase to extremely high levels that can exceed 480/350 mmHG. This is extremely dangerous, and usually occurs when the lifter holds his breath during a heavy lift. However, resting blood pressure after regular resistance training may lower or stay the same, notes Jack H. Wilmore and David L. Costil, authors of Physiology of Sport and Exercise.