(NaturalNews) Heart attack survivors are often instructed by their doctors to get as much cardiovascular exercise to stay heart healthy and avoid recurrent and deadly heart attacks. A staff scientist at the Lawrence Berkeley National Laboratory in Berkeley, California, has found somewhat conflicting evidence. He gave a word of caution to heart attack survivors everywhere. "More isn't always better," said study researcher Paul Williams, referring to exercise for heart attack survivors.

Dr. James O'Keefe, cardiologists at St. Luke's Mid-America Heart Institute in Kansas City, Missouri, chimed in as a co-author for an editorial of the new Berkeley study:"It's not good to be sedentary, but you can overdo [exercise]."

When 2,377 heart attack survivors were monitored over the course of 10 years, the Berkeley researchers found an important correlation. For heart attack survivors, too much exercise can more than double cardiovascular risk.

How much exercise is too much for heart attack survivors?

According to the study, published in the Aug. 12 edition of Mayo Clinic Proceedings, cardiovascular disease deaths rose sharply for those who exercised the most. For running, risk of death increased sharply when patients ran more than 4.4 miles per day (7.1 km). For brisk walking, risk of death increased sharply when patients walked more than 6.6 miles per day (10.7 km). In those 10 years of study, 526 people passed away and about 75 percent of those deaths were due to recurrent heart attacks.

Still, daily exercise levels that fell below 4.4 miles of running per day or 6.6 miles of walking per day benefited heart attack survivors immensely. The smaller increases in daily exercise routines reduced participants' risk of dying from a heart attack by up to 65 percent.

The researchers recommend that cardiologists encourage heart attack survivors to exercise more, but to not overdo it. Running more than 30 miles per week, or walking beyond 46 miles, actually has the opposite effect on cardiovascular system recovery. Those who exercised excessively only made up a small fraction of the study participants, 6 percent, but this group had a more than double rate of recurrent heart attacks that lead to death during those 10 years.

Dr. Carl Lavie, medical director of cardiac rehabilitation and preventive cardiology at the John Ochsner Heart and Vascular Institute in New Orleans agreed with the study from a general health standpoint, "[Y]ou don't have to do a lot of exercise to get a lot of benefit."

Study author Paul Williams pointed to the Physical Activity Guideline for Americans as a good starting point for exercise levels. This chart recommends 150 minutes a week of moderate-intensity exercise or 75 minutes of vigorous-intensity exercise for most Americans. Williams said it's okay to exceed the recommendation of the chart but not to go beyond the limits highlighted in this study, especially if one is a heart attack survivor.

Sources for this article include:

http://consumer.healthday.com

http://www.mayoclinicproceedings.org

http://www.counselheal.com

http://science.naturalnews.com