On the heels of research suggesting too much running could lead to an earlier death, two new studies say too much high-intensity exercise could lead to heart problems.
The first, conducted by German researchers, followed more than 1,000 people mostly in their 60s, who had existing heart disease and had enrolled in an exercise program to prevent further heart health issues. As hypothesized, the least physically active people were at increased risk for heart problems and earlier death. But the most active group, those who did daily strenuous physical activity, also had increased risk of dying of heart problems than people who were active only two to four times a week, according to the study.
In the second study, Swedish researchers surveyed more than 44,000 men between the ages of 45 and 79 about their physical activity habits at various ages throughout their lives. Researchers also monitored the heart health of the men for an average of 12 years, looking in particular for atrial fibrillation, a type of irregular heartbeat. The most active men -- those who completed intense exercise for more than five hours a week -- were 19 percent likelier to have developed an irregular heartbeat by age 60 than men who exercised for less than an hour a week. Among men who exercised more than five hours a week when they were younger but for less than an hour a week by the time they reached age 60, irregular heartbeat risk jumped to an increase of 49 percent. However, older exercisers were less likely to develop atrial fibrillation than their peers who didn't exercise at all.
Both studies, published in the journal Heart, "describe a similar U-shaped or reverse J-shaped pattern for the dose-response effect of exercise: maximum cardiovascular benefits are obtained if performed at moderate doses, while these benefits are lost with (very) high-intensity and prolonged efforts," Spanish researchers wrote in an accompanying editorial.
While the studies add to mounting evidence that more exercise isn't always better, the editorial authors reiterated that some is still better than none. "The benefits of exercise are definitely not to be questioned; on the contrary, they should be reinforced," they write. "The studies reviewed here, and future studies, will serve to maximize benefits obtained by regular exercise while preventing undesirable effects -- just like all other drugs and therapies."