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MONDAY, March 16 (HealthDay News) -- Any exercise program can improve blood flow after a heart attack, but the benefit vanishes just four weeks after exercise is stopped, a new Swiss study finds.

"The main goal of our study was to determine the impact of different types of exercise on vascular [blood vessel] function," said Dr. Margherita Vona, director of the Cardiac Rehabilitation Center at the Clinique Valmont-Genolier in Glion sur Montreux. "The conclusion was that in our patients, after a heart attack, all types of exercise were useful for correcting vascular dysfunction, without any difference among aerobic, resistance or combined training."

But the improvement in blood flow seen in the 209 heart attack survivors enrolled in the program was lost four weeks after they stopped exercising, according to the report in the March 31 issue of Circulation.

"These data imply that good, long-term adherence to training programs is necessary to maintain vascular benefits on endothelial dysfunction," Vona said.

The endothelium is the inner lining of blood vessels. Its failure to perform efficiently increases the risk of a blood clot that can block an artery, causing a heart attack.

Participants in the trial were randomly assigned to aerobic training, resistance training, a combination of aerobic and resistance training, or no training at all.

Those who did aerobic training had four weekly sessions, including a 10-minute warm-up, 40 minutes of cycling that increased the heart rate to 75 percent of maximum and a 10-minute cool-down. Resistance training had four weekly sessions of 10 exercises with weights and rubber bands, lasting 45 seconds to one minute, with recovery intervals of 15 to 30 seconds.

Endothelial function was measured by flow-mediated dilation (FMD), the amount that blood vessels widen to increase blood flow. FMD more than doubled, from 4 percent to 10 percent, in both exercise groups. There was no significant change in FMD in the non-exercising participants.

However, the increase in FMD was lost a month after the regular exercise program ended.

"This aspect is particularly important in patients with coronary artery disease, in whom correction of endothelial dysfunction could help to slow the progression of atherosclerosis and probably avoid new cardiovascular events," Vona said.

None of the exercises caused problems for the participants, she added.

The resistance training program followed American Heart Association guidelines, Vona said. "Following the guidelines of the American Heart Association, all people can do resistance training," she said. "Many papers show beneficial effects of resistance training on cardiac and muscle function, in normal people and also, for example, in diabetic subjects."

The study does add some insight to the well-worn subject of exercise and the heart, said Dr. Johnny Lee, an assistant clinical professor of medicine at Mount Sinai Medical Center in New York City.

One is about the type of exercise that should be done, Lee said. "Most of the time, we tell patients about aerobic exercises -- running, jogging and swimming," he said. "We haven't thought that resistance exercise, lifting weights and the like, can have an equal benefit. This shows that it does. That there was benefit from aerobic exercise was no surprise. What was a surprise was that resistance exercise gave equal benefit."

Second, the loss of benefit after exercising stopped that was seen in the study participants, who by definition are in the highest cardiac risk group because they have had heart attacks, carries a message for lower-risk people, Lee said.

"If this applies to the sickest patients, that if you stop you are going to lose the benefit, it shows that continuing to exercise can only have a positive effect if you are a normal subject with no heart disease," Lee said.

More information

A guide to exercise after a heart attack is offered by the American Heart Association.