With about 31 percent of the adult population having high blood pressure, understanding how your heart pumps blood around your body is important. Different conditions, such as posture, weight, exercise, stress and diseases of the arteries, can all have an impact on the amount of pressure your heart uses to supply your body with nutrients. Moving from a standing to a supine, or lying on your back, position can also prompt a variation in blood pressure.
Blood Pressure
Without blood pressure, your body could not receive the oxygen, nutrients and other important biochemicals it needs to function adequately. You need blood pressure in order to move blood against the force of gravity. According to the National Heart Lung and Blood Institute, blood pressure is the measure of the force of blood against artery walls. Because the heart has two motions, contracting and relaxing, blood pressure is recorded as two numbers, one over the other. The systolic pressure is the actual beat of the heart while the diastolic pressure is when the heart relaxes. Systolic pressure is listed over diastolic pressure to give readings such as 120 over 80, which is considered normal.
Variation
As your body's need for oxygen increases, such as when you are working out, your blood pressure can increase. In contrast, your blood pressure should be lower when you are relaxed or at rest. Stress or excitement can also cause a rise in blood pressure, as can conditions where your arteries are narrowed by plaque buildup, states MayoClinic.com.
Supine
When you are lying on your back, in a supine position, blood is able to flow more easily to your brain and feet because gravity is evenly affecting your body. The heart does not have to fight against gravity to push blood to your brain. The supine or reclining position is favored by practitioners to measure your blood pressure because it is less stressful on the body.
Standing
If you move from a seated or supine position to a standing position, there may be a momentary drop in your blood pressure, according to the American Academy of Family Physicians. This drop occurs because your body experiences a temporary drop in blood volume as 300 to 800 mL of blood pools in your legs. However, MayoClinic.com states that special cells called baroreceptors sense this drop and signal the heart to beat faster. Blood vessels will then contract and increase pressure to pump the blood upward. Thus, after an initial drop, you experience a rise in blood pressure when moving from a supine position to standing. For some people, they exhibit a severe drop in blood pressure during this movement, which is a condition known as orthostatic hypotension.
Orthostatic Hypotension
If your blood pressure drops drastically when you stand up after lying down or sitting, you can experience dizziness, blurred vision, nausea and even headache. According to the American Academy of Family Physicians, orthostatic hypotension occurs if your systolic blood pressure decreases at least 20 mm/Hg or your diastolic blood pressure decreases at least 10 mm/Hg within three minutes of standing. Because it is normal to experience a slight drop in pressure, it is not uncommon to feel slightly lightheaded upon standing; however, if this feeling lasts for a few minutes and happens frequently, talk to your doctor.
