Americans as a whole don’t exercise nearly enough, as evidenced by the obesity epidemic. As a result, many Americans face numerous health conditions, including diabetes, cancer and heart disease. But can there too much of a good thing when it comes to exercise? How much exercise is enough? The answer may not be so simple.
In a report recently published in the Journal of the American College of Cardiology, researchers from Denmark suggest that people who exercise too hard or too much may actually be at just as great a risk of premature death than those who don’t exercise at all.
Researchers looked specifically at running and found that people who ran at a fast pace more than four hours a week for more than three days a week had about the same risk of dying as those who were sedentary—even after researchers accounted for potentially compounding factors such as age, sex, heart health history, diabetes, smoking and alcohol consumption.
In this particular study, those with the lowest risk of dying during the 12-year study period were those who ran less than three times a week for one to 2.4 hours at a slow to moderate pace. Both too little running and too much running are linked to higher mortality rates, and the most intense runners had a risk of dying similar to that of someone who would rather sit on the couch.
Authors of this study did acknowledge, however, that it is possible other factors common to avid runners, such as sun exposure, could increase their risk of skin cancer, which might explain the higher risk of dying during the study.
In a review of studies from the past 30 years, Dr. Paul Thompson — chief of cardiology at Hartford Hospital in Connecticut and a dedicated marathon runner — and his colleagues examined the evidence that extremes of endurance exercise may actually increase cardiovascular disease risk. What Dr. Thompson and his cohorts found is that there is no evidence that exercise is dangerous for a normal, healthy person.
Frequent training can, however, cause changes in cardiac physiology and structure, which may mimic heart damage, though these changes are typically short-term with no long-term effects.
Dr. Thompson and his colleagues found that for people who are predisposed to heart problems, such as a buildup of plaques in the arteries — a condition known as atherosclerosis — too much strenuous exercise may indeed be dangerous. If an individual has a buildup of plaque in the arteries, exercise is more likely than sitting to cause the plaques to rupture, leading to a heart attack.
Similarly, people with a hereditary heart abnormality, such as an enlarged heart (cardiomyopathy), may have a greater risk of complications with strenuous exercise—complications that could lead to premature death.
“The best evidence remains that physical activity and exercise training benefit the population, but it is possible that prolonged exercise and exercise training can adversely affect cardiac function in some individuals,” writes Dr. Thompson and his co-authors.
How much exercise is enough?
The proper response to the research is not to avoid exercise altogether, but to know your family history of heart conditions and sudden death. It doesn’t take extreme exercise to reap the heart health benefits of exercise.
Spend one to four hours a week no more than three days a week jogging at a slow to moderate pace. Walking, swimming and cycling are other forms of exercise you can do to improve your cardiovascular health.
Before beginning any exercise regimen, talk to your doctor about your family history to determine whether you need to be tested for conditions that could make strenuous exercise dangerous. When you do exercise, pay attention to any symptoms you may experience during exercise, such as extreme or unusual fatigue, shortness of breath or chest pain.