For weekend warriors or amateur athletes, new studies show that "excessive exercise" can make you sick, not healthy. But how do you measure what is excessive?
This week Runner's World asked two researchers behind recent studies on the damaging effects of over-exercising to see what they think is overkill. Marathon training? A four-hour bike ride on Saturday?
Cardiologist Chip Lavie, a veteran runner with a marathon best of 3:04, had his name on two exercise studies that have attracted a lot of recent attention, notes Runner's World.
In one study, he and his team found a lower all-cause mortality rate among runners averaging about 15 miles a week, while those running longer distances had a higher mortality rate (the highest risk was still lower than nonexercisers).
When it comes to determining what's excessive, "it's hard to put an exact number on it," he said. "There's a tremendous amount of variability when you look at age, ability, activity levels, intensity, prior history and even genetics."
He adds: "We can't pick one point for everyone, be it 10 miles a week, or 15 or 20 or 25. For some people, running a half marathon is harder than a marathon is for others. A marathon might not be very hard if you're well trained for it. But as a general point, if you exercise hard for 3, 4, or 5 hours, a number of people may have adverse effects."
"The benefits of exercise are analogous to a powerful drug; indeed if we had a pill that does everything that exercise does, most of us cardiologists would go out of business," adds researcher James O'Keefe, M.D., who coauthored a recent study on bad heart-related outcomes sometimes seen in distance runners. "Still, like any potent drug, an ideal dose exists: enough to get the full benefit but not so much as to cause dangerous side effects."
His best advice: "The latest data from our studies and others strongly suggests that the ideal dose of daily vigorous exercise is about 30 to 60 minutes."