Some doctors caution people with heart failure against pushing themselves too hard physically. But a new analysis of past studies suggests heart patients may actually benefit more from relatively intensive exercise.
Researchers found people with heart failure had a 23-percent improvement in heart function after taking part in relatively high-intensity exercise programs. That compared to a 7-percent improvement among those in low-intensity programs.
"I think we need to open up our eyes and really ask ourselves, ‘Does high intensity equal higher risk or does it mean higher rewards?'" said Neil Smart, the study's lead author.
"I personally think it's not higher risk," he told Reuters Health. "I think it means higher rewards."
Smart is an associate professor at Australia's University of New England in Armidale, New South Wales.
About 5.8 million people in the United States have heart failure, according to the National Institutes of Health (NIH).
The condition occurs when the heart can't take in enough blood or adequately pump enough blood to the rest of the body. There's no cure, but the NIH says doctors can help people manage the condition to improve the quality and length of their lives.
One strategy that has been tested among people with heart failure is exercise training, such as the kind that exists within cardiac rehabilitation programs.
People who have had heart attacks and other cardiac problems like heart failure may take part in those programs to get medical supervision while learning to safely exercise and manage their condition.
Smart and his colleagues write in JACC: Heart Failure that past analyses have found exercise helps improve breathing and heart health among people with heart failure.
But the largest trial to compare people in an exercise program to a comparison group showed smaller improvements than expected. Many of the people in that trial stopped exercising during the study, which may have made it harder to see an effect.
For the new analysis, the researchers looked at randomized controlled trials, which are considered the gold standard of medical research.
They found 74 studies that compared 3,265 people in exercise programs and 2,612 in non-exercise groups.
Of people randomly picked for exercise programs, 241 were put on high-intensity training programs. Another 2,215 worked out at a vigorous intensity, 672 at a moderate intensity and 137 at a low intensity.
The intensity is relative to each participant's ability. That means high intensity for a heart failure patient may be a brisk walk for a healthy adult.
Exercise programs lasted anywhere from four to 52 weeks.
At the beginning of the study, each participant's peak oxygen consumption was used as a measure of heart health. Peak oxygen consumption increases with how effectively the body is using oxygen during exercise.
Between the beginning and end of the programs, oxygen consumption increased by 23 percent among people exercising at a high intensity. That compared to about a 7-percent increase among those in the low-intensity groups.
A 23-percent increase in peak oxygen consumption would be noticeable to people with heart failure, according to one expert who was not involved with the new study.
People with heart failure would notice they are no longer tired after their daily care, said Gordon Blackburn, an exercise physiologist and program director of cardiac rehabilitation at the Cleveland Clinic in Ohio.
Blackburn also said it's a large enough difference to suggest there could be a reduction in deaths among people in the high-intensity exercise groups. The study, however, did not find that to be the case. It also showed no differences in deaths and hospitalizations between exercise groups.
"In a supervised cardiac rehabilitation environment, it's suggesting we can be more aggressive with these patients, but we have to pay attention to the whole disease," Blackburn said. "The patient has to be stable with their heart failure managed."
He noted that it's important people know this analysis is based on data collected during closely controlled and supervised programs.
"I would hate to think that someone with heart failure would go out and think, ‘I'm going to push myself,'" Blackburn said.
Smart also cautioned that all exercise should not be intensive. Instead, a fraction of a person's program should be spent on high-intensity exercises.
"I still think we need a bit more evidence before we make people exercise a bit more," he said.
"This isn't definitive, but it's a good start."