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Resting & Non-Resting Blood Pressure
Author: Cleaves M. Bennett MD FACP
Monday, January 07, 2008

How much pressure should there be in the arteries? What really is normal blood pressure—and I don't mean normal in the sense of average, I mean healthy, A-okay for humans, optimal?

Is 120/80 (that's the number most of us learned in medical school) really the answer?

I think these questions require a little explanation.

Basically, we need just enough pressure to keep the blood circulating to all parts of the body. And what that really means is that we need enough pressure to make sure the blood reaches the highest point—the brain.

Getting the blood to circulate to the rest of the body doesn't require much pressure at all—since gravity would do most of it anyway. There's no problem getting blood to your feet—unless, of course, you're standing on your head!

So the circulatory system is really designed to run at a fairly low pressure, about 80/40 or 90/50 mm Hg. In certain cultures (on the Solomon Islands, the Cook Islands, and in central New Guinea, for example) it stays about that level throughout people's lives. No need for 120/80. No needs for “essential” hypertension as you grow older. There's absolutely nothing essential about it.

Young children in our culture usually start with a blood pressure around 80/40, but it rises progressively with increasing age. Yet for most of us there's certainly no need for this increase. It's not optimal. It just happens.

If we were giraffes, of course, things would be different. Giraffes actually need to have high blood pressure, at least enough to lift the blood all the way from the heart, up all that long neck, to the brain. But unless you're a giraffe you can probably get by just fine with a blood pressure of 80/40 or 90/50, and you certainly don't need a systolic pressure that's higher than 100 at rest.

I've reassured a lot of patients about their new "low" blood pressure. When you're on an excellent low-salt, low-fat diet, exercising daily, losing weight, and relaxing—really taking are of yourself—your early morning blood pressure might be 85/52, or 90/56, something like that. "Are you sure it's okay, Doc? My pressure's never been that low," my patients say. I smile and tell them, "You're standing up, aren't you? Not feeling faint? Don't worry, that's the blood pressure you're supposed to have!"

So when we know a little bit about blood pressure we see that 120/80 isn't all that great, really. It's just a pretty darn good pressure for most of us, about as low as you usually see it in an adult living the "good" American life. But we'll talk more about your life style and what it does to blood pressure later.

By the time we try to define what high blood pressure is, or what qualifies as the disease of hypertension, we're really just picking numbers. Most all the experts agree that the lower your blood pressure is the better off you are.

The only reason to pick out a pair of numbers and say that anyone with blood pressure above them has "hypertension" is to know at what point to start giving medicines. If you don't have to give any medication, then the lower the blood pressure the better.

And by the way—low blood pressure doesn't produce a tired or rundown feeling. In the chapters on exercise, when we get into the program itself, we'll find out the real reason why so many people think they need Geritol!

If you can learn to get your blood pressure to be less than 100/50, great—because you're probably better off than if it's 110/60 or 120/80. But nobody would be willing to start you on medicines to get your pressure that low, that's for sure.

Most doctors now would call anything above 140/90 hypertension. That's the figure the American Heart Association uses, and it's the most common definition. However, you should know that a recent study showed that there was a higher risk of vascular disease associated with a diastolic pressure of 90 than with one of 80, and certainly if my own systolic pressure was consistently above 130 or 135, I'd want to do something about it.

The real truth is that the lower your blood pressures the better off you are.

Non-Resting Blood Pressure

So far we've been talking about blood pressure at rest. Rest; think about what that means. The dictionary puts it this way. Rest: to cease from effort or activity for a time. It means to be at peace, or be tranquil. It's an unusual state for modern man or woman, this state of rest, don't you agree?

What happens to your blood pressure when you're not at rest? There are, of course, a number of circumstances in which it's appropriate for your blood pressure to go up when you're not at rest. When the body has to meet a challenge or deal with stress, the emergency or sympathetic nervous system turns on. For a small stress (the toast is burned) it may turn on a little; for a big challenge (your son wrecked your new car) it turns on a lot. Your heart beats more rapidly and forcefully on these occasions, delivering more blood into the arteries, and the blood pressure rises. This happens whenever you get even a little bit excited or angry or tense. And it also happens when you exercise.

In a normal, healthy person who is exercising vigorously, the systolic pressure may go as high as 180 or even 200. This increase is due to the fact that, when you exercise, the heart fills up more fully and also empties more completely. When you're exercising extremely hard, your heart may be pumping out seventy-five to eighty percent or more of the blood it can hold with every stroke, whereas at rest the fraction is nearer fifty percent.

Not only that the venous reservoirs in your body deliver more blood into the active circulation, and more blood is returned rapidly to the heart. Cardiac output (the amount of blood pumped by your heart in one minute) can rise tenfold in these ways. Diastolic pressure, which might be driven up by the rise in systolic pressure and cardiac output, actually falls because the arterioles in the vascular beds in muscle and skin open up so completely.

Psychological stress can also raise the blood pressure. When the emergency (sympathetic) nervous system switches on to enable you to handle a stressful situation, your body prepares itself for one of two reactions: fight or flight. In fact, the stress response is often known as the fight or flight response.

What does this mean? For thousands of years the main threats to human beings were predators—wolves, tigers, other humans, or whatever. And the best ways to deal with them were either by fighting them or getting away fast. Usually the latter!

Both these ways of dealing with unpleasant situations call for drastic action—and so the body prepares itself by partially shutting down the blood flow to such organs as the stomach, bowels, and liver, shifting some blood stored in reservoirs on the venous or low pressure side into the heart and arteries, and getting ready to send an enormous amountof blood to the muscles. Adrenalin and other hormones pour into the bloodstream to give us strength and energy to deal with the crisis. And the heart beats more forcibly and rapidly.

When you feel threatened, it's not often a tiger that's bothering you. It may be a problem at the office or a run-in with your teenage son who won't cut his hair. And fighting the office problem—or the son—or running away from them at top speed—just isn't going to help.

The body is all prepared for fight or flight—and there's nowhere to go. Nothing physical is happening, or likely to happen. Oh, there may be some yelling if it's your son, but that doesn't use enough muscles to burn up all the energy you have ready to go. As a result, all the extra blood that's been readied for use by the muscles isn't in fact needed. Meanwhile, the hormones are still in the bloodstream, stirring things up—and there you are, cooking; right?

In situations like this your blood pressure remains high because your heart continues to beat more forcefully and rapidly, and the extra bloods still there . . . and that's the effect of stress on blood pressure.

What is stress?

Of course we all know that when people or things or situations push us or bump into us too much we get upset—and that's stress. Usually we associate stress with upset—anger, fear, unpleasant emotions. And most of us put the blame on someone or something outside us. It's the job; it's my mother, my husband. Maybe you blame it on the neighbors, or their kids.

For people with hypertension, however, the emergency nervous system is on a good deal more than they're aware of it. It's on even when they are not upset.

I remember a lawyer in his fifties from Miami. Just coming in my office sent his pressure up 30 to 40 mm Hg. And he liked me! That's the amazing part. He enjoyed our visits. He had absolutely no feeling of apprehension, anxiety or upset when he came to see me. Nothing seemed to be telling him, "Look out! Emergency! Emergency! Get ready to fight or flee!" No alarms going off in his head. He was totally unaware of the reaction that was going on in his own body.

Do you notice the reaction that takes place in you when you do mental arithmetic? Drive fast on the freeway? Watch a football game, or an exciting movie? Try noticing in your own life how often you are provoked, or excited, or turned on, or annoyed.

In some especially sensitive people the emergency nervous system goes on at almost every interaction they have with other people, indeed at most every kind of sensory input, unless it's very, very soothing and mellow.

And it doesn't happen only with other people. Man versus machine can have the same effect. It's not just the vacuum cleaner or your automobile anymore—we've got some real creative annoyances in our lives right now. The computer! Ever try to close a bank account and have the computer keep billing you service charges for a year?, backed with compound interest running at twenty percent? And how about answering machines? I know my blood pressure goes up when I ring someone up and one of those damn machines comes on the line!

It's all very simple and straightforward. None of these processes are mysterious. You know that when you're walking or running your blood pressure is going to go up, and come down again when you relax. And you know that when you're upset at the boss (or the telephone) your blood pressure goes up, and once again, it will come down again if you can relax.

That's the trick, isn't it? Letting go of the upset, completely!

And the main difference between these two kinds of stress is that running may well help your blood pressure in the long run, and getting mad at the boss is more likely to make things worse for you both physically and economically.

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Stephen Hales was the first man ever to measure blood pressure.
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Breathe a sigh of relief, because even if you show up in a doctor's office today with severe high blood pressure the chances are nobody's going to recommend the use of surgery. When I started in medical school a surgical procedure known as sympathectomy was commonly used in the treatment of severe high blood pressure. It involved cutting all the nerves of the sympathetic nervous system (involved in the stress response) along both sides of the spine. It was a pretty drastic procedure but it was the best option we knew about in some cases. It probably even saved lives. Read More