If they start in time, middle-aged people could reduce or reverse their risk of heart failure from years of sedentary living with a 2-year program including high- and moderate-intensity aerobic exercise.
This was the conclusion of a recent study, led by researchers from the University of Texas Southwestern in Dallas and published in the journal Circulation, that revealed that exercise can reverse damage to aging hearts.
However, the cardiologists who carried out the research emphasize that the exercise must be done at least four to five times per week.
The team had shown in an earlier study that two to three times per week is not enough to protect against heart failure.
"Based on a series of studies performed by our team over the past 5 years," explains senior study author Benjamin D. Levine, who is a professor of internal medicine at the University of Texas Southwestern, "this 'dose' of exercise has become my prescription for life."
He urges people to exercise as "part of their personal hygiene," similar to showering and brushing teeth.
Heart failure is a serious condition in which the body's cells do not receive a sufficient amount of oxygen and nutrients because the heart muscle is too weak to pump enough blood.
This leads to symptoms such as fatigue, shortness of breath, coughing, and difficulty carrying out everyday things such as climbing stairs, walking, and carrying shopping.
Heart failure can be ongoing, or chronic, or it can be acute and develop suddenly. Although it can affect younger people as well, it is one of the most common reasons that people aged 65 and over are admitted to hospital.
Estimates made in 2016 suggest that there are around 5.7 million people living with heart failure in the United States, and only around half of those with the condition survive for longer than 5 years following diagnosis.
The heart has four chambers that pump blood in an organized way: a left and right upper chamber, or atrium, and a left and right lower chamber, or ventricle.
Blood depleted of oxygen comes in from the rest of the body into the right atrium and then goes out to the lungs through the right ventricle. The lungs enrich the blood with oxygen and it travels back to the heart, entering the left atrium. This oxygen-rich blood is then pumped back out to the rest of the body through the left ventricle.
One of the measures that is used to diagnose heart failure is the ejection fraction, or the amount of blood that the left ventricle pumps out with each heartbeat.
Ejection fraction is considered normal if it is in the range of 50–70 percent. This means that 50–70 percent of the total volume of blood in the left ventricle is pumped out each time the heart beats.
An ejection fraction of 40 percent or less might be evidence of heart failure. If it is 41–49 percent, it might indicate borderline heart failure, but not necessarily; other conditions, such as a heart attack, can also reduce ejection fraction.
However, you can still have heart failure if your ejection fraction reading is normal — this is called heart failure with preserved ejection fraction (HFpEF).
In their study paper, the researchers note that HFpEF is often preceded by a loss of heart muscle elasticity. This increased "cardiac stiffness" is also associated with poor physical fitness in middle age.
Stiffened heart muscle
In earlier research, cardiologists from the University of Texas Southwestern had found that middle-aged people who do not exercise and are unfit often have a smaller, stiffened left ventricle that does not pump blood very well.
In contrast, they observed that this is not the case in very fit athletes and even in non-athletes who exercise on 4 to 5 days per week over decades. Instead, their heart chambers remain large and elastic.
In other research, Prof. Levine had found significant improvement in "cardiac compliance," or reduction in heart muscle stiffness, from a year of exercise training in young people, but no such improvement in people aged 65 and over.
Therefore, in the new study, the team wanted to find out whether or not more intense, prolonged aerobic exercise can restore elasticity in stiff heart muscles of middle-aged people whose lives have been largely sedentary.
They recruited 53 participants aged from 45 to 64 who were healthy but largely sedentary — that is, they spent a lot of time sitting and did not exercise very much.
A program with high-intensity 'four-by-fours'
The investigators randomly assigned the participants to one of two groups — the exercise group or the control group — in which they undertook 2 years of exercise and underwent various tests of heart function.
The control group participants completed 2 years of regular balance training, yoga, and weight training on 3 days per week.
The exercise group participants undertook a 2-year progressive exercise program comprising high- and moderate-intensity aerobic exercises on 4 to 5 days every week.
The progressive exercises included working up to doing "four-by-fours," during which the heart rate is monitored. These exercises consist of four sets of 4-minute exercises wherein the heart works at 95 percent of its maximum heart rate, followed by 3 minutes of "active recovery," during which the heart rate is 60–75 percent of its maximum.
The scientists defined maximum, or peak, heart rate as the level of heart rate measured when the participant was working as hard as they could while still able to complete the 4-minute exercise.
At the end of the study, the results showed that overall, the exercise group became fitter. They increased the amount of energy that they used during exercise — measured as the volume of oxygen uptake — by 18 percent.
There was also a noticeable reduction in cardiac stiffness.
There were no such improvements in the control group. It appears that exercising only two or three times per week was not enough to protect the heart against the effects of aging, says Prof. Devine.
"But," he adds, "committed exercise four to five times a week was almost as effective at preventing sedentary heart aging as the more extreme exercise of elite athletes."
'Exercise 4–5 days per week' to stay healthy
Prof. Devine says that they also found that the time to start exercising is in late middle age, "when the heart still has plasticity."
"I recommend that people do 4 to 5 days a week of committed exercise as part of their goals in preserving their health," he urges.
He suggests a similar program to the one that the participants undertook in the study. This should include:
- at least one long session per week lasting around an hour of cycling, walking, tennis, or aerobic dancing
- one high-intensity aerobic session per week, such as four-by-four interval training
- one session of strength training per week
- two or three sessions of moderate-intensity exercise per week
Moderate-intensity exercise is that which still causes you to perspire but is not so intense that you cannot carry on a conversation.
Because the study included mostly white volunteers who wanted to take part and were physically able to do so, the findings may not apply to the population in general or to other racial groups, explain the researchers.
"The key to a healthier heart in middle age is the right dose of exercise, at the right time in life."
Prof. Benjamin D. Levine