Blood pressure and heart rate go hand in hand in most people’s minds. After all, these two vital signs usually are measured at the same time at the doctor’s office. But each measures distinctly different factors related to your heart health. Blood pressure is the force of blood flowing against the walls of your arteries, while heart rate — sometimes called pulse — is the number of times your heart beats every minute. Below, cardiologist Luke Laffin, MD, explains some key differences — and busts some common myths along the way.

1. Blood pressure and heart rate are always linked

False: It is true that blood pressure and heart rate often rise and fall together, Dr. Laffin says. When you face danger, for example, your blood pressure and pulse may both jump upward at the same time. However, if your heart rate rises, that doesn’t automatically mean your blood pressure will rise — or vice versa. “When the two are disconnected, you may be looking at a specific problem,” Dr. Laffin says. “For example, if you are dehydrated, bleeding or have a severe infection, blood pressure typically decreases and heart rate increases.”

2. Blood pressure and heart rate have “normal” target numbers

False: There are guidelines, but what’s normal varies from person to person. Optimal blood pressure typically is defined as 120 mm Hg systolic — which is the pressure as your heart beats — over 80 mm Hg diastolic — which is the pressure as your heart relaxes. For your resting heart rate, the target is between 60 and 100 beats per minute (BPM).

Keep in mind that heart rate and blood pressure are a customized fit. You need to work with your doctor to establish a baseline that’s normal for you.

3. A low pulse or blood pressure always indicates a problem

False: What’s healthy for one person may indicate danger for another. For example, a fit person may have a resting heart rate in their 50s or, in some cases, even their 40s. “It can actually be a sign of being in really good shape,” Dr. Laffin says. Low blood pressure can be a bit trickier, especially in older patients and those with heart disease. If you’re in danger from low blood pressure, your body will tell you. “It’s really about how you feel,” Dr. Laffin says. “Are you feeling weak? The numbers on their own don’t tell the story; it’s the numbers paired with the symptoms you may have.”

4. High blood pressure is more dangerous than a high heart rate

True: Again, what’s considered normal varies. But Dr. Laffin says there is enough clinical evidence to suggest that when blood pressure is even a little over your typical average over time, the risk for heart disease and stroke go up. The physical effects of high blood pressure take their toll on your blood vessels. “Essentially, for each increment of 20 mmHg over 115 mmHg systolic, your risk of heart attack, stroke, heart failure or chronic kidney disease doubles,” Dr. Laffin says. Elevated heart rate can be a sign of danger, too, but the cause-effect relationship is not so clear. “Studies show that people who have faster baseline heart rates are more likely to have cardiac problems and premature cardiac death,” Dr. Laffin says. “But we’re not sure whether that is the cause of the problem or just a sign of what’s going on. The most common cause of a high resting heart rate is being deconditioned (in other words, out of shape).”

5. When you measure matters

True: To measure your resting heart rate and blood pressure, pick a reliable and reproducible time, Dr. Laffin advises. Ideally, check in the morning before medications and occasionally in the evening, around dinner time. Don’t take your readings right after exercising — unless you’re trying to establish a baseline for what’s called active blood pressure and heart rate. During readings, you want to be in a resting position with your legs uncrossed. Many people don’t realize that crossing your legs while taking a reading may cause an eight to 10 point increase in systolic blood pressure. Which measure is more important? This depends on your health, too. For patients with atrial fibrillation, heart rate might be more important to watch, but many other heart diseases depend more on blood pressure. To be saf e, measure both. “Almost all automated kits you buy at a store provide blood pressure and pulse on one readout,” Dr. Laffin says. “It’s convenient — and knowing both numbers helps better understand how to make lifestyle and medication adjustments.”

6. The faster the heart rate, the shorter the lifespan

True: In a large study of people going for a health checkup in China, those who had a high-normal resting heart rate of 80 bpm to 90 BPM had a 40 percent shorter lifespan than those with a desirable heart rate of 60 BPM to 69 BPM. However, the good news is that 15 minutes to 30 minutes of daily moderate exercise, such as brisk walking, could eliminate the increased mortality and reverse the life-span loss, the researchers say. The study underlines the important role that physical activity can play in keeping your heart healthy — and giving you a longer life, Dr. Laffin says. “Even moderate activity has benefits,” he says. “So there is no longer any reason to stay on the couch.”