May 7, 2014
News Review From Harvard Medical School -- Another Reason to Boost Exercise with Age
Older adults who keep up or increase their exercise may have improvements in a measurement of the heart's electrical health. That's the conclusion of a study of 985 adults. Their average age was 71 when the study began. Everyone in the study wore a monitor to record the heart's rate and rhythm for 24 hours. People wore the monitor again for a day 5 years later. They also answered detailed questions about physical activity at the start of the study and 3 years later. Researchers focused on a measurement called heart-rate variability. This is the name for differences in the time between one heartbeat and the next. The heart rate tends to become less variable as people get older. But this study found better heart-rate variability among older adults who got more exercise. This was especially true for those who increased their exercise over time. The journal Circulation published the study. HealthDay News wrote about it May 5.
By Howard LeWine, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
You might think that a healthy heart is one that ticks at a very steady beat, like the second hand of a clock. But the reality is quite different. A healthy heart constantly changes the time interval between heartbeats. It's responding to what's happening throughout the rest of your body.
These changes between heartbeats are not something you can detect by taking your pulse. They are too small -- just milliseconds. But they can be measured using an electrocardiogram hooked up to a computer. While not ready for prime-time use by your doctor, this may be an important measure of heart health in the future.
As we age, our heart rate varies less. But you can help maintain your heart-rate variability with walking and other leisure-time activity.
In this new study, the researchers looked at the relationship between heart-rate variability and physical activity in older adults. People who walked the fastest and farthest had more heart-rate variability than those who seldom exercised.
The authors suggest that maintaining heart-rate variability may be an important reason that staying physically active throughout life lowers your risk of heart attack or heart failure.
The concept of heart-rate variability is hardly new. It was first suggested in the mid-1700s by a Swiss scientist named Albrecht von Haller. He concluded that the beat of a healthy heart isn't absolutely regular. Modern tools have proved him to be absolutely right.
What Changes Can I Make Now?
Neither you nor your doctor can measure your heart-rate variability. Even if there was a simple way to measure it, we really don't know how much useful information it provides. Other, simpler measurements that you can do yourself might be just as good, or even better.
For example, you can keep track of your resting heart rate as you increase your amount of physical activity. In general, as your fitness improves, your resting heart rate will fall. If you take a certain type of heart medicine, such as a beta blocker, your heart rate will already be slow. In that case, you might not see any change.
It's best to take your resting heart rate when you first wake up and before you get out of bed. You need a clock or watch with a second hand. Feel your pulse at your wrist or in your neck. Count the number of beats for exactly 15 seconds and multiply by 4. That gives you the number of beats per minute.
An even better test for heart health is heart-rate recovery after exercise. Measure your heart rate as soon as you finish your sustained, moderate-intensity exercise. Measure your heart rate for 15 seconds and multiply by 4. Stop, rest and wait 60 seconds. Measure your heart rate again the same way. Continue this for a few minutes. Your heart rate should fall by at least 12 beats per minute.
Heart-rate recovery is also something you can track as you ramp up your physical activity. Here's an example. If walking is your main exercise, you should aim to walk a little faster and a little longer each week. Repeat the heart-rate recovery test regularly. You can expect to see your heart rate recover more quickly over time.
What Can I Expect Looking to the Future?
If heart-rate variability is to become an important predictor of heart health, we will need much more research to prove it.