Running and the risk of death: Can it be too much of a good thing?
A large study on the impact of high intensity running on mortality was reported in the February issue of the Journal of the American College of Cardiology. In this study, 1098 runners were compared to 3,950 sedentary non-runners from 2001 to the present and their survival rates were compared. They then divided the running population based the intensity of the weekly exercise to see if the extent of exercise impacted survival.
Last year we reported that marathon runners seemed to have a higher risk of death than other types of runners but this was from smaller studies that provided a lower strength of evidence. In this newest study, running was associated with a lower risk of death than being sedentary and doing no running at all. However, they found that the running subgroup with the most vigorous exercise were almost twice as likely to die as the sedentary population while those doing mild to moderate exercise were less likely to die than those doing no exercise. Greater than 4 hours of running a week at a fast pace was associated with this higher risk. It was actually the mild exercise group, those doing 1 to 2.4 hours of running per week at a slow or average speed of 5 mph or less that derived the most benefits.
All of these studies are based on self-reports of running length and intensity and so we are not certain that the differences in survival are directly related to running. It is very difficult to do the definitive study type to truly answer this question. However, it seems that exercise, like water, food, vitamin, and mineral intake is a double-edged sword. Too little or too much of any of them can be harmful and the secret to good health is balance. The high adrenaline rush and physical demands stresses the heart and can damage it. People who run many marathons have been found to have heart scarring suggesting that driving the body to continue past the point of exhaustion is dangerous. During a marathon people’s body temperatures can rise to dangerous levels. Dehydration can result and drinking water to cool the body can cause low blood sodium which can be damaging to the body.
The government suggests 2.5 hours of exercise a week is optimal which is right in line with this study’s result. Running to compete in a 5K might actually be healthier over the long run than trying to become a marathon runner and it is much easier to fit in a busy schedule. No study suggests that just sitting at home is a good option so get out there and exercise, just do it in moderation.