A normal blood pressure reading is 120/80 mmHg. The first number indicates the systolic pressure; this is the pressure within your arteries while your heart is contracting and propelling blood throughout your body. The second number is the diastolic pressure; this reading indicates the pressure within your arteries between heartbeats. Diastolic pressure is a useful measurement when evaluating a patient for cardiovascular health. This value normally increases in males during exercise.
Effects of Exercise on Blood Pressure
According to the book "Hurst's The Heart," it is completely normal to experience increased diastolic pressure during exercise. Increased heart rate will lead to an increased diastolic pressure because there is less time for the blood to move away from the heart in between contractions. If there is more blood pumped into your arteries, pressure will be elevated during the diastolic phase of the cardiac cycle. Additionally, there is a flood of adrenaline circulating in your blood during exercise. This chemical acts on your heart as well as your blood vessels to increase cardiac output and decrease blood vessel diameter, respectfully. This arterial contractile force will also act to elevate diastolic pressure during exercise.
Consequences of Increased Diastolic Pressure
It is not only normal for diastolic pressure to increase during exercise; it is actually helpful for providing oxygen to the heart itself. The only time your heart receives blood flow is during diastole; when the heart muscle is not contracting, the coronary arteries are able to perfuse this tissue. When you heart rate increases during exercise, your heart muscle needs more blood and oxygen to function properly. Elevated diastolic blood pressures allow this demand to be met.
Decreased Diastolic Pressure
While it may seem counter intuitive, a decreased diastolic pressure during exercise is actually a bad thing. Normally, when your heart contracts and forces blood into the circulation, the aorta will dilate to accommodate the increased pressure and volume. This is helpful to maintaining a constant flow of blood to your organs. If blood only moved when the heart was contracting, you would have short periods of time in which no blood or oxygen was being delivered to your brain and other vital organs. To fix this problem, your aorta is designed to act as a capacitor; it "stores" energy during heart contractions to power the flow of blood during diastole, or between contractions. This is why it is not normal for your diastolic pressure to decrease during exercise. If this were the case, your aorta would not be properly acting as a capacitor, and the constant flow of blood to your organs would be interrupted.
Applications
If you have observed elevated diastolic blood pressures during exercise, then you have witnessed your body responding to physical activity in a normal and healthy way. Diastolic pressure can be a useful indicator of cardiovascular health, and should be considered a measurement of baseline arterial pressure between heartbeats. Pulse pressure, or the difference between systolic and diastolic pressure, is something your doctor will keep an eye on. When you exercise, both systolic and diastolic pressures are expected to increase. It is only when the difference between these measurements becomes significant that you begin to run into problems. Increased pulse pressures may indicate a stiff heart, which is unable to properly relax and fill with blood during the diastolic phase of the cardiac cycle.
References
- MayoClinic.com: High Blood Pressure (hypertension); Sheldon Sheps; December 2008
- "Hurst's The Heart: Normal Physiology of the Cardiovascular System"; Brian Hoit and Richard Walsh; 2010
