My brother-in-law has high blood pressure and a family history of stroke. So in addition to taking antihypertension medication, he practices an exercise program developed by his trainer. The problem:His doctor informed him that exercise can elevate his blood pressure (and in fact he takes scheduled breaks during his workout so that his blood pressure can return to normal). He’s walking a difficult line in doing his best to keep healthy — but I’m happy to say that now a small study from University of Texas (UT) Southwestern Medical Center has shed at least some light on this tricky issue.
Before we get into the study findings, it will help to have a little background in how people with normal blood pressure respond to exercise. Any type of exercise triggers a need for increased blood flow to the exercising muscles. Seeming to counteract that, however, is the fact that exercise also stimulates activity in the nervous system that can constrict blood vessels (vasoconstriction). This would seem to set the stage for actually decreasing blood flow during exercise. Luckily this doesn’t happen in people with normal pressure thanks to an ingenious mechanism called functional sympatholysis, which the UT study discovered for the first time. Amazingly, this system blunts vasoconstriction and keeps blood flowing as needed to the working muscles.
The lead author of the hypertension study — which included 13 people with hypertension and 17 with normal blood pressure — was Wanpen Vongpatanasin, MD, director, hypertension section, cardiology division at UT Southwestern Medical Center. She told me that all participants performed a mild form of exercise — rhythmic squeezing of a hand grip. This was sufficient to activate muscles in the arm to trigger the nervous system response, and in the group with normal blood pressure, it also triggered the functional sympatholysis mechanism that blunted vasoconstriction in the muscles. But functional sympatholysis did not happen in people with high blood pressure. In fact, her study showed that having high blood pressure apparently impairs this protective mechanism along with its steadying influence. This is just what people like my brother-in-law don’twant to hear.
An additional finding of the study was that when people who have high blood pressure exercise, it stimulates the release of a hormone called angiotensin II. This hormone causes blood vessels to constrict, which in turn causes high blood pressure in some people. To further test the finding, for four weeks the study group with high blood pressure took a type of hypertension medication that blocks the hormone.
Then, for another four weeks, the group instead took a different type of hypertension drug called a thiazide diuretic, which does not block angiotensin. The finding: While the ARB drug had readily restored the functional sympatholysis mechanism in spite of hypertension, the thiazide drug did not — at last, pointing to a way for people with high blood pressure to exercise with less worry!
Dr. Vongpatanasin says that that people with high blood pressure can exercise safely by following certain guidelines. Although we still have much to learn about this subject, she says we do know that gentle exercising, such as brisk walking, easy bicycling, yoga and the like, are safe and, indeed, regular participation in them is encouraged. However, more intense workouts, such as heavy weight lifting, may be risky for hypertensive people. To determine if you are in the safe zone when doing more demanding workouts, Dr. Vongpatanasin advises checking your blood pressure immediately following a workout. (Do-it-yourself cuffs for monitoring pressure are inexpensive and useful to have.) Doing this every few weeks provides enough monitoring information, but if you see pressure headed toward the range of 220/120, she says, your exercise is too intense and you need to moderate it. And — the new strategy — if you are not taking an ARB type of drug, you might want to discuss with your doctor whether it would be an appropriate choice for someone with your medical profile.
