Too much exercise can be as risky as too little exercise for patients who already suffered a heart attack, according to new research by the Department of Energy’s Lawrence Berkeley National Laboratory.
The research followed 2,377 subjects who had suffered a heart attack before they enrolled in the laboratory’s National Runners’ and Walkers’ Heath Study. About 10 years later, 376 of the participants had died of cardiovascular disease.
When researchers crunched the numbers, they found that the exercise sweet spot for heart attack survivors is running up to 30 miles or walking up to 46 miles per week. Those who got that much exercise showed a 70% lower risk of a cardiovascular death than subjects who didn’t run or walk.
However, more exercise did not mean a better outcome for study subjects. Those who ran more than 30 miles per week were twice as likely to die from heart disease.
“The results are surprising,” says life sciences researcher Paul T. Williams, who co-authored the study with Paul D. Thompson. The work appears in the upcoming issue of the Mayo Clinic Proceedings.
William says previous research has shown that the risk of nonfatal heart attacks decreased the more patients ran, at least through 40 miles per week. Further, there were no indications “that things got worse at higher mileages,” he says.
But, the new research suggests that, “Like other medical treatments, there appears to be a level that can be excessive,” Williams says.
The new study also shows that current public health recommendations of 150 minutes per week of moderate-intensity exercise, like brisk walking, may not be the best thing for heart attack survivors.
“The current finding underscores the importance of precisely defining the dose-response relationship between exercise and its health benefits,” Williams says.