The adverse effect of lack of exercise on the blood pressure is well known. A sedentary life frequently leads to chronic hypertension, and in turn, high blood pressure can lead to heart, brain, and kidney damage.
We will address the topic of chronic hypertension in a separate article. Today, we will discuss a phenomenon called “hypertensive response to exercise” which can occur in seemingly healthy subjects who have no history of hypertension but whose blood pressure during exercise seems to increase “too much.”
As a brief background, we should point out that the blood pressure varies all the time, even from one minute to the next. The reason being that the pressure inside the arteries reflects the intensity of movement of the blood throughout the body, and this movement changes all the time in response to the changing needs of the body and to multiple factors.
Many organ systems participate in the control of the blood pressure at various times, including the heart and blood vessels, the nervous system, the kidneys, and some hormonal glands. Regulation of the blood pressure is a very complicated matter.
To be sure, the blood pressure is expected to rise during exercise (in particular, it is the systolic blood pressure that goes up), and it returns to normal within a few minutes of rest.
In some people, however, the rise in blood pressure seems “excessive” or above the level of increase habitually seen. Cardiologists and exercise physiologists who encounter this effect during a treadmill or stationary bicycle stress test call this phenomenon a “hypertensive response to exercise” (we’ll abbreviate it HRE) or, alternatively, an “exaggerated blood pressure response to exercise.”
The phenomenon of HRE immediately raises several questions:
- Can we define HRE precisely? Is there a specific number over which one can say for sure that the blood pressure during exercise is “too high”?
- What is the significance of HRE in the short term? Is it dangerous?
- What is the the significance of HRE in the long term. Is it a marker of future risk of hypertension?
- Could it be that HRE occurs primarily during stress tests, but not when people are exercising for recreation?
1) Is there a cut-off number? Unfortunately, the answer to this question is “no.” There is no standard, satisfactory threshold number that allows us to confidently separate people who demonstrate HRE and people who do not. Since the blood pressure varies so widely depending on a number of factors, identifying specific cut-off numbers is elusive or misleading. Some researchers have used a systolic blood pressure cut-off value of 200, others 210, and still others 220 to define HRE. The inability to define a cut-off point makes the other questions difficult to answer also.
2) What are the short-term effects of HRE? For the most part, if everything else seems OK, the subject feels fine, and there are no abnormalities on testing, most experts agree that having HRE is not by itself a cause for concern during exercise, so athletes who demonstrate HRE (however defined) should not be alarmed on that basis.
For some people, however, the elevation in blood pressure with exercise is accompanied by other signs of problems. They may feel particularly short of breath, and the ECG may become abnormal. If images of the heart are taken during such cases, it is not uncommon to see that the heart is struggling and not squeezing as well as it should. This more worrisome response typically occurs in people who have more advanced underlying cardiovascular disease. Such cases may indicate that treatment for high blood pressure should be intensified.
3) What are the long-term effects of HRE? Unfortunately, because HRE is hard to define precisely, studies are not providing clear-cut answers to this question. Some scientists think that HRE could be an early sign of hypertension. In other words, the person is at a stage where the blood pressure is high during exercise only, but in a few years, it may be high at rest as well. This concern has not been confirmed in all studies looking at the long term effects of HRE.
A recent study using a new and sophisticated ultrasound technique has suggested that the hearts of people with HRE may be under subtle strain during exercise. At this time, this finding must be considered preliminary and is not by itself a cause for concern.
4) Could it be that HRE occurs only because of the stress of the stress test? There is no good answer to that question because it is hard to measure exercise blood pressure accurately outside of a clinic environment, or at least, it has not been done on a large scale.
There is some reason to think that HRE could be equivalent to “white coat hypertension,” which describes the fact that some people have a high blood pressure only when they go to the doctor, but not when they are more relaxed at home. One study showed that some people who have HRE during a stress test may not have it again if the stress test is repeated a separate time. Having gone through it the first time, the subjects may be more relaxed the second time.
On the other hand, even if HRE is “stress” related and equivalent to white coat hypertension, that does not mean that it is completely benign. People whose blood pressure increase excessively because of stress seem to be at slightly higher risk of long term cardiovascular complications compared to those whose blood pressure is always in a normal range.
What is the take home message from all this?
Generally-speaking, we are not too concerned by HRE, but here is our approach:
First of all, we make sure that our instruments are well calibrated and we measure the blood pressure during exercise manually. There is wide consensus that the automated devices are not reliable during exercise, and even with careful manual measurement, only the systolic blood pressure can be noted with reasonable accuracy.
When we encounter high blood pressure during exercise but all other signs are healthy, we do not raise any alarms. Routine monitoring of the blood pressure during an annual physical examination is normally sufficient.
If there are other subtle signs of concern during the comprehensive examination, we may suggest closer monitoring or additional testing. Ambulatory blood pressure monitoring is a relatively new technique that measures the blood pressure automatically during a 24-48h period of time. The test provides a lot more information than the standard blood pressure measurement at the doctor’s office, and in some countries (the United Kingdom, for example), it has become a routinely ordered procedure to screen for hypertension. Some other tests that measure arterial elasticity may also be of value.
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