It’s been a painful week for exercise.
First, a review of six studies of physical exercise found that 10 percent of the subjects—people who exercised regularly—actually experienced a decline on one of four common measures of heart disease (blood pressure, insulin, HDL cholesterol, and triglycerides). Seven percent scored worse on two measures. So, for reasons that aren’t clear right now, for a small but meaningful group of adults, exercise does the opposite of what you want it to do. Researchers controlled for the obvious possible explanations—age, race, gender, medication—but could find no way to determine who might fall into the adversely affected 10 percent.
The research also found the exercise led to “an exaggeratedly good response on at least one measure” for another 10 percent. So we’re intrigued and interested but we’re going to call this one a wash. Winners and losers in about equal proportions. Nothing that would spook us away from the gym.
The second research story is a little more sobering. The Mayo Clinic reports that “chronic training for, and competing in, extreme endurance exercise such as marathons, iron man distance triathlons, and very long distance bicycle races may cause structural changes to the heart and large arteries, leading to myocardial injury.”
The study appears in the June issue of Mayo Clinic Proceedings. In its press release, the clinic notes that the condition (which it calls “Phidippides cardiomyopathy” after the courier who ran from Marathon to Athens to bring news of the Greek victory over Persia and then dropped dead, presumably from the exertion) could explain the recent death of Micah True: “the pathologic changes in the heart of this 58 year-old veteran extreme endurance athlete may have been manifestations” of the condition.
While noting the widely documented benefits of exercise for many conditions—including a reduced risk of heart disease, hypertension and obesity—the researchers also pointed to previous studies that suggest overdoing it brings risks. “In one study, approximately 12% of apparently healthy marathon runners showed evidence for patchy myocardial scarring, and the coronary heart disease event rate during a two-year follow up was significantly higher in marathon runners than in controls….Endurance sports such as ultramarathon running or professional cycling have been associated with as much as a 5-fold increase in the prevalence of atrial fibrillation.”
The docs at Mayo suggest that you can still give yourself a pretty good workout. If you pound the treadmill for a half hour or even twice that, you see benefits. But it tapers off fast after that: “Beyond 30-60 minutes per day, you reach a point of diminishing returns.”
Apparent bottom line: overuse it and lose it. The first “it” refers to your heart; the second to your life.
Oddly erotic painting of Pheidippides by Luc-Olivier Merson, 1869, via Wikimedia Commons.
