(RxWiki News) Exercise is a crucial part of a healthy lifestyle. But for some people, it appears there is such thing as too much exercise.
Two recent studies looked at the relationship between physical activity and heart health.
For the first study, researchers tracked the physical activity habits of patients with heart disease.
They found that patients who engaged in moderate physical activity had the lowest rates of stroke and heart attack, compared to both inactive patients and very active patients.
The second study tracked rates of irregular heartbeat among adult men who reported their exercise habits as a teenager, 30-year-old and 60-year-old.
The researchers found that vigorous exercise at age 30, especially when followed by a sedentary lifestyle by age 60, was tied to an increased risk of irregular heartbeat.
"Work with your doctor to figure out physical activity levels that are safe for you."
Ute Mons of the Division of Clinical Epidemiology and Aging Research in the German Cancer Research Center led the first of these two studies.
Previous research has shown that physical activity has helped to decrease the risk of heart disease in healthy adults. This study by Mons and colleagues looked at how different amounts of exercise affected heart disease patients.
These researchers recruited 1,038 participants with heart disease for their study. All participants were 30 to 70 years old and were being treated for heart disease.
The majority of the participants were overweight, older than 60, and current or former smokers.
Over 10 years, the participants periodically reported the amount of strenuous exercise they performed.
The researchers kept track of how many cardiovascular events, such as heart attack or stroke, took place over the course of the study.
Mons and team found that about 40 percent of the participants were active two to four times per week. About 10 percent reported that they rarely or never exercised.
The most heart health problems occurred among the group who engaged in physical activity the least. This group had a twofold risk of developing a heart problem compared to the group of moderately active participants.
The group that exercised two to four times per week experienced the least major heart health events.
The researchers also noted that the most frequently active participants also experienced more heart health problems compared to the moderately active group. However, the most active group still had fewer heart problems than the least active group.
The researchers suggested that the participants who exercised two to four times per week were reaping the most heart health benefits from their physical activity.
Nikola Drca of the Department of Cardiology at the Karolinska Institute led the second of these two studies.
Drca and team collected data about 44,410 men and their exercise habits.
These men were free of atrial fibrillation at the start of the study. Atrial fibrillation is an irregular, very fast heart beat that increases the risk of heart failure and stroke.
Participants reported how much they had exercised at age 15, 30 and 50. The researchers followed up with the men for an average of 12 years.
During the follow-up period, 4,568 participants developed atrial fibrillation.
The researchers found that men who exercised for five hours or more per week at age 30 were 1.19 times more likely to develop an irregular heartbeat than those who exercised for less than one hour per week.
On the other hand, men who reported walking or bicycling regularly at age 60 were less likely to develop atrial fibrillation than those who did not walk or bike.
Drca and colleagues suggested that physical inactivity is a far more problematic health issue than getting too much high-intensity exercise.
However, they also noted that frequent high-intensity physical activity in midlife was tied to irregular heartbeat later in life.
These studies were both published in Heart on May 14.
The first study was funded by the German Federal Ministry of Education and Research and the Willy Robert Pitzer Foundation. The researchers disclosed no competing interests.
The second study was funded by the Swedish Research Council and the Karolinska Institute. One researcher reported receiving consultancy fees from Medtronic.