Exercise used to be considered potentially dangerous for people with heart failure. However, two major studies are showing that may not be the case.

In fact, the research has found it can improve patients' quality of life.

When Lise Coleman was diagnosed with heart failure, doctor's orders were to take it easy.

"They told me to do nothing, basically, they didn't want me to even lift a basket of clothes. I was scared to do anything," she said.

Heart failure is a condition in which the heart is unable to pump enough blood to meet the body's needs.

Like many patients, Coleman went on medication to try to control her symptoms of fatigue, shortness of breath and swelling in her legs.

She also enrolled in HF-Action, the largest clinical study of its kind, to look at the safety and efficacy of exercise training among those with moderate to severe heart failure.

"We thought, 'What was most important was to see if we could influence keeping these patients out of the hospital, whether for any cause or for heart failure, and whether we could prolong their life,'" said Dr. Kathryn Flynn of the Duke Clinical Research Institute. "Equally important is quality of life. Could we improve their quality of life?"

The study enrolled over 2,300 patients, dividing them into a usual care group and an exercise group.

The groups were followed for an average of 30 months.

The study findings are published in the Journal of the American Medical Association.

Modest improvements were found across the board, when it came to the safety and medical benefits of exercise and the effect on quality of life.

"Exercise training is safe in patients with advanced heart disease. Second, we showed a modest improvement in clinical outcomes, a reduction in hospitalization or death," said Flynn.

Patients in the exercise group reported improvements in their quality of life greater than patients in the usual care group did, and the improvements occurred early and they were sustained over time.

Although the study has ended, Coleman is still exercising, and is a firm believer in the benefits.

"When you exercise, you're helping your heart pump the blood through your body, you're helping your organs, you're helping yourself feel good, and when you feel good, you can do more, so exercise has been life changing for me," she said.