Why is my blood pressure lower after exercise

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General responses to selected questions from Joel Braunstein, MD, of Johns Hopkins University and Joseph Toscano, MD.

Question:

I am 6 foot tall and weigh 210 lbs. and have been exercising regularly for the past year. Oftentimes my blood pressure before exercise will read, for example, 145/89, but after exercise will read lower, such as 117/79. Is this normal? I feel great. Thanks for your help.

Answer:

Normally, blood pressure increases from resting level with exercise. Based on criteria used for exercise treadmill tests, any decrease in blood pressure during exercise might be a sign of heart disease. The same is true, to a lesser extent, if there is a failure of the blood pressure to increase with exercise. Once exercise has stopped, blood pressure should return to resting levels and may even drop to slightly below pre-exercise levels for a while based on a number of factors, like any medications one might be taking, overall fitness level, and the type and duration of exercise.

The whole question of what your fall in blood pressure really means depends on its timing. If it occurs during exercise or soon after stopping, talk to your doctor about having some sort of stress test (an exercise treadmill test or a stress echocardiogram), because, even though you feel well, this could be a warning sign of early heart disease. It may not be, but the exercise testing will help sort this out. If your blood pressure increases with exercise, then gradually decreases to a lower than pre-exercise level after something like 10 minutes or more, this may be fine. If you are still concerned, then having a stress test to be sure would not be a waste, especially given your age and the fact that you are a male. If you have any risk factors for heart disease (smoking, high blood pressure, diabetes, high blood cholesterol levels, or close relatives with heart disease before age 45), then a treadmill test might be an even better idea.

An interesting related topic has to do with "recovery time," or the time it takes someone's heart rate to return to resting levels after peaking during exercise. Recovery time depends on several factors, the most important of which is a person's level of conditioning. For this reason, there doesn't seem to be much predictive value of a certain recovery time as far as heart disease goes. There is some information, however, that specific rates at which the heart rate falls after exercise can predict increased cardiac risk, though this seems to apply only to those who are already known to have heart disease. For example, in those known to have heart disease, studies have shown that if the heart rate falls by less than 13 beats per minute (BPM) in the first minute after stopping exercise (e.g., you peak at 150 and it doesn't get below 137 after one minute) or by less than 42 BPM after two minutes of stopping (e.g., you peak at 150 and don't get below 108 after two minutes), there is an increased risk of dying of the underlying heart disease.

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When to Worry About Low Blood Pressure After Exercise

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Exercise is effective at lowering blood pressure, especially when you work out on a regular basis. But can physical activity lower blood pressure too much? Here's what you need to know about blood pressure during and after exercise and when you need to worry.

What’s in a Number?

When you exercise, two important indicators of its impact on your system are your blood pressure and your heart rate.

Your blood pressure is created by your heart when it pumps blood into your arteries and when the arteries resist the blood flow. This pressure against the artery walls gives you your blood pressure number. Systolic pressure — represented by the top number — indicates the pressure while your heart contracts, pumping blood into your body. The diastolic pressure —represented by the lower number — is the pressure when your heart is at rest between beats.

Your heart rate is the number of beats per minute. At rest, it could be anywhere from 60 to 100 beats. The lower the number, the better shape you're in — it can go even lower for well-conditioned athletes — even 40 beats per minute, according to the Mayo Clinic.

Because the heart is a muscle, exercise can help it become stronger and function more efficiently. Exercise also keeps arteries flexible, allowing for good blood flow and normal blood pressure. To enhance your heart health, your heart rate should reach 50 percent to 85 percent of its maximum during workouts, depending on whether you're doing a moderate or vigorous workout.

Your personal max is 220 minus your age, so it will go down slightly with every passing year, according to guidelines from the American Heart Association. During exercise, your heart pumps faster and harder to increase blood flow to muscles, and blood pressure increases as your heart rate goes up.

However, one effect of exercise is that, afterwards, it can lower your blood pressure. A drop in blood pressure after exercise is called post-exercise hypotension, and it's normal to see your systolic number (typically it's the only one affected) decrease by 5 to 20 millimeters of mercury, or mm Hg, and stay there for hours, according to research published in the October-December 2015 issue of Hypertension Journal.

What's more, consistent exercise is one way to keep normal blood pressure from rising as you get older and to keep high blood pressure consistently lower. For some people, it might be all that's needed to control slightly elevated blood pressure. Aim for 30 minutes on most days of the week, recommends the Mayo Clinic.

Why Your Cooldown Is So Important

For heart health to improve in a safe way, you need to gradually lower your heart rate after exercise. In fact, according to research published online February 2017 in the Journal of Applied Physiology, recovery after exercise is when many of the physical benefits of exercise happen. After exercise, your cardiovascular system is in a unique state, different from both rest and exercise, with the drop in blood pressure just one example of this.

The cooldown is an important part of this transition from exercise to rest. If you stop exercising suddenly, your heart slows down, decreasing blood circulation and making your blood pressure fall too quickly, which can lead to dizziness and even fainting. Instead, do 5 to 10 minutes of light activity to gradually start the process of bringing your system back to normal.

Sometimes your blood pressure can fall beyond what's expected after exercise. This can happen for a variety of reasons.

The type and duration of the exercise, how much water you lose through sweat and whether you exercise in the heat are factors that can lead to a drop in blood pressure. Rehydrating, particularly when exercising in hot and humid conditions, can make you less vulnerable, according to the Hemodynamics of Hypertension report.

But if your blood pressure frequently drops when you go from lying down to sitting up or from sitting to standing, you may have what's called orthostatic or postural hypotension. (Take your blood pressure, and you could see a drop from 120/80 to 100/70 within minutes of changing your position.)

Age may be a cause of postural hypotension. When you sit or stand, blood pools in the legs — they act like reservoirs. "As we get older, the system that sends blood back up slows down; it's not as efficient as it used to be, so you might feel dizzy while it's adjusting," says John A. Osborne, MD, PhD, a cardiologist who specializes in hypertension and preventive cardiology and medical director of State of the Heart Cardiology in Southlake, Texas. Your cooldown should help your body adjust.

You can experience postural hypotension as a side effect of having anemia, diabetes or Parkinson's disease. "If it happens after exercising, it could be related to taking blood pressure medication, especially if you're new to it," says Dr. Osborne. The medication plus exercise have a combined effect, temporarily bringing it down too low. "It can take time to find the right dose," he explains. "You might need to tweak the time of day you take it and the time of day you exercise, or switch to a different medication. It's important to work with your doctor to find the right formula."

The effect can be even more pronounced if you're on more than one medication, such as an ACE inhibitor and a diuretic. That combination plus the natural drop in blood pressure from exercise can leave you feeling dizzy and even faint. That 5-to-10-minute cooldown after each and every exercise session becomes even more essential, according to the American Council on Exercise.

Regularly taking your blood pressure is a must. You might not be aware of fluctuations if you don't have symptoms. "Use a monitor that goes on your upper arm, not your wrist, for accuracy," Dr. Osborne says.

Other warning signs of blood pressure that's fallen too low are:

• Feeling lightheaded or confused
• Blurry vision
• Weakness or fatigue
• Nausea

Talk to your doctor if you experience any of these symptoms after exercise.

If you're diagnosed with postural hypotension, always take your time when changing positions and hold on to a fixed object for balance, recommends Michigan State University, because the dizziness can make falling more likely. Avoid exercises that call for bending over and straightening up quickly, yoga poses that have your head below your heart and exercises with rapid changes in posture, like jump squats or burpees. Avoid rapidly going from one standing exercise to a sitting one and vice versa, such as from squats to sit-ups or push-ups to lunges.

When Blood Pressure Drops During Exercise

This is a concern because it could be a sign of certain types of heart disease. One way doctors check for that is with a treadmill test.

Under normal circumstances, your blood pressure will go up with exercise, typically in increments of 20 mm Hg, depending on the intensity of the workout, and then come down afterward. "The more quickly it comes down, the better shape you're in, and the more it's delayed, the more you're deconditioned," explains Dr. Osborne.

However, blood pressure that falls during a stress test can be a sign of severe coronary artery disease — blockages in your arteries. Studies have shown that a drop of 20 mm Hg during exercise can put you at risk for a cardiac event, so the American Heart Association guidelines are to stop a treadmill test if blood pressure falls by even 10 mm Hg.

Researchers also have found that a rise in systolic pressure can be a warning sign as well if it's too small — less than the expected 20 mm Hg increase that exercise should cause, according to a May 2015 study in the Journal of the American Heart Association.

Signs of low blood pressure during exercise include chest pain and light-headedness, fainting and whiteouts — when your field of vision goes white, says Dr. Osborne. Always stop immediately if you experience these symptoms and call your doctor right away.