I recently started running. Now I am certainly not a fast runner, but have endurance. The first couple of weeks it was all I could do to get a couple of miles in, then I was able to gradually increase my endurance and can now do 7 miles in a day and run 6 days per week. It is pretty addicting, as you begin to feel great! So I came across this post today and had to share it with you. Just like everything there is moderation to consider even with exercise. What does that mean for my run? Some day’s 2 miles is just fine, and have a couple of distance runs each week.
The not-so-long run: Mortality benefit of running less than 20 miles per week
JUNE 6, 2012 Michael O’Riordan
“We were thinking that at some dose of running, things would level off, that we’d see that runners would have a reduction in mortality at certain distances and then it would kind of level off,” Dr Carl Lavie (Ochsner Health System, New Orleans, LA), one of the study investigators, told heartwire. “The fact that it reached its plateau at such a low level is surprising, as is the fact that it didn’t level off but actually went the other way. We never had a point where runners did worse than nonrunners, but really, if you put it in almost a joking way, it showed that if you ran enough you got yourself back to the level of a couch potato. You lost the survival advantage.”
The results of the study were presented last week at the American College of Sports Medicine (ACSM) 2012 Annual Meeting by lead researcher Dr Duck-chul Lee (University of South Carolina, Columbia). Lavie stressed that while the study is one of the largest performed to date, including data on more than 52 000 men and women participating in the Aerobics Center Longitudinal Study (ACLS), it is a retrospective analysis and that results will likely vary among individuals with differing athletic abilities or different ages.
“There is not going to be a set cut point where we say this is the magical amount of running,” said Lavie. “But certainly, it looks like you get the benefits at relatively low, modest amounts. If you shoot for superhigh amounts of running, you’re certainly not getting more benefit, and it actually appears from our data that you could be getting less benefit.”
Running linked with a 19% lower risk of death
In the ACLS, participants were free from cardiovascular disease, cancer, electrocardiographic abnormalities, and diabetes at baseline. Running and other physical activities were self-reported on the medical history questionnaire, and patients were followed for an average of 15 years. During this time, 2984 deaths occurred and approximately 27% of the men and women participated in running as a form of exercise.
Overall, running was associated with a 19% lower risk of all-cause mortality when compared with individuals who did not run (hazard ratio [HR] 0.81; 95% CI 0.73-0.89). As noted, the researchers observed a U-shaped relationship with all-cause mortality, with faster paces, longer distances, and increasing frequency suggestive of a diminishing mortality benefit.
Regarding pace, individuals who ran six and seven miles per hour had a significant 21% and 27% lower risk of all-cause mortality, whereas those who ran eight or more miles per hour had a nonsignificant 7% lower risk of all-cause mortality. Running up to 20 miles per week was associated with a significantly reduced risk of death, with the largest benefit observed in those who ran between 10 to 15 miles weekly (HR 0.73; 95% CI 0.60-0.89). For those who ran 20 to 25 miles and more than 25 miles per week, however, there was a nonsignificant 10% and 5% reduction in all-cause mortality. Similarly, the mortality benefit was observed in individuals who ran two to five days per week, but the benefit began turning in the other direction when subjects ran six or seven days per week. At six and seven days, the reduction in all-cause mortality was not statistically significant.
“Honestly, my weekly running mileage is above the level where we’re seeing the benefit,” Lavie told heartwire. “I average 35 to 40 miles a week, and in many previous years have probably averaged more than 45 or 50 miles per week. I’ve done a few marathons and a ton of half-marathons, so I sure would have liked to have seen the benefit leveling off rather than going the other way.”
Lavie noted that it is impossible to say definitively that more running is making the reduction in all-cause mortality go in the other direction, as it’s possible that unmeasured variables might have influenced the results. That said, the group corrected for the usual variables—age, gender, hypertension status, lipid levels, smoking status, and alcohol intake, among others. It’s possible that runners might not be taking care of themselves in other ways, offered Lavie by way of explanation, although he didn’t think that was plausible. “I would have thought that runners are more likely to be more health conscious,” he said.
Review article highlights the running risk
As for the underlying mechanisms, Lavie highlighted a review paper published this week in the Mayo Clinic Proceedingsby lead author Dr James O’Keefe (Mid America Heart Institute of St Luke’s Hospital, Kansas City, MO), of which he was a coauthor, highlighting the potential for adverse cardiovascular remodeling among individuals who participate in long-term endurance exercise, such as marathons, ultramarathons, Ironman-distance triathlons, and long-distance cycling races . Regular and intense endurance exercise such as these events might lead to myocardial fibrosis, particularly in the atria, interventricular septum, and right ventricle, which in turn can lead to atrial or ventricular arrhythmias. Endurance exercise may also be associated with coronary artery calcification, diastolic dysfunction, or arterial stiffening.
Dr Benjamin Levine (University of Texas Southwestern Medical Center, Dallas), an expert in the effects of exercise on the heart, told heartwire that he believes concerns about endurance exercise, even long-term events like marathons and ultramarathons, are overblown. In fact, another exercise study presented at the ACSM meeting showed that right ventricular mass increased following six months of endurance exercise, but the ratio of left ventricular mass to right ventricular mass was unchanged, a finding that is suggestive of a physiological adaptation to exercise. Levine was not involved in any of the studies or with the writing of the review paper.
“We have studied some of the most extraordinary athletes on the planet,” said Levine. “We’ve done invasive studies, very high-resolution studies of cardiac and vascular performance, and elite endurance athletes, including young and elite master athletes, have no evidence of fibrosis whatsoever. They have youthful, compliant hearts and blood vessels.”
He added that his group has also analyzed data from the Cooper Center Longitudinal Study (CCLS), examining outcomes among individuals who ran two to three days per week, four to five days per week, and those training at an elite master’s level. After performing MRI scans, they saw no evidence of myocardial scarring as evidenced by delayed gadolinium enhancement. In fact, he contends that casual recreational activity, performed two to three days per week, is not enough to change cardiac compliance, whereas lifetime running at 30 miles per week makes cardiac compliance equivalent to healthy 30-year-olds regardless of age. In the CCLS study, those who exercised four to five times per week had aortic and cardiac compliance approaching values achieved by the master athletes.
“I think there are a lot of good things that happen when you only exercise a few times per week,” he said. “There are changes in autonomic function and endothelial function, but I wouldn’t disagree with you that there must be some level, occasionally, where people can hurt themselves running. I think the evidence is quite compelling that exercise in untrained people does increase the risk. It increases the risk of thrombosis, it increases the risk of an arrhythmia, and every time you exercise that risk goes up a little bit. We know that exercise does transiently increase cardiac risk, but over time the overall risk is clearly lower.”