This item from The Wall Street Journal uses a cheeseburger metaphor to drive home the idea contained in some recent studies that endurance running may not be all that good for you.
Before my couch potato friends start saying, "Ha! I knew it -- pass me some more chips, please," the point is not that exercise is bad for you -- it's that too much exercise may not be as good for you as a moderate amount.
[There is] mounting evidence that extraordinary doses of exercise may diminish the benefits of modest amounts ... That extra six years of longevity running has been shown to confer? That benefit may disappear beyond 30 miles of running a week, suggest recent research.
The improved blood pressure, cholesterol levels and robust cardiac health that exercise has been proven to bestow? Among extreme exercisers, those blessings may be offset partially by an increased vulnerability to atrial fibrillation and coronary-artery plaque, suggest other recent studies.
In the face of this research, long-standing skepticism about the possibility of "exercise overdose" is softening among many sports physicians. "The lesson I've learned from 40 years of cardiology is that when there's this much smoke, there's often some fire," said Paul Thompson, a sports-medicine specialist and veteran marathoner who is chief of cardiology at Hartford Hospital in Connecticut.The breaking point suggested in the article is thirty miles a week -- which I've never achieved, much less maintained. I checked my records (yeah, I keep a log of my exercise -- yet another symptom of my OCD) and the most I've ever done in a week is 28.8 miles. When I get on a roll, I may do five-six miles four or five times a week (usually it's five miles three or four times).
So if a potato is worried that if he gets up off the couch he might accidentally start running more than thirty miles a week, I can reassure him that there's little danger of it happening any time soon.
There may be no danger anyway. The other side of the story:
Yet sports-medicine specialists are sharply divided over whether any warning is warranted. For every American who exercises to extremes, after all, there are thousands who don't exercise at all—and who might embrace any exercise-related warnings as cause for staying sedentary. Moreover, the evidence for extreme-exercise hazards is far from conclusive—and is contradicted by other studies suggesting the health benefits of exercise may accrue to infinity.
"It's true that the majority of cardiovascular protection comes from exercise at more moderate levels, but there is compelling evidence that there's no upper limit," said Benjamin Levine, director of the Institute for Exercise and Environmental Medicine in Dallas and professor of medicine at the University of Texas Southwestern Medical Center.And, besides, I love cheeseburgers.