Higher mileage provides no more longevity benefit, according to the research summary. In fact, running more than 20 miles a week may erase some of the gain. "The low-dose runners had lower levels of fitness than higher-dose runners but appeared to get maximal protection against cardiovascular and all-cause mortality," Lavie told Runner's World by email.
This seeming paradox has previously been called the "excessive exercise hypothesis." Now the researchers are using a different term, "cardiotoxicity."
"We're not trying to scare anyone," said Lavie. "We just think athletes and their clinicians should be informed. The chance of a very serious risk is probably small."
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The paper notes that 52 minutes of running per week is less than the U.S. government guidelines, which recommend 75 weekly minutes of vigorous activity like running.
According to the current guidelines, one minute of running is equivalent to two minutes of light exercise like walking. The new paper's authors find that the correct ratio is more like 1:3 or 1:4. That is, one minute of running is worth three to four minutes of walking. This is true because running is a very vigorous exercise, even at paces of 10:00 to 12:00 minutes per mile. In addition, some health researchers say, many walkers move along too slowly to get optimal benefits from walking.
In their conclusion, the authors write, "The overall benefits of running far outweigh the risk for most individuals, and are associated with considerable protection against chronic diseases and CVD [heart] and all-cause mortality."
The Mayo summary gained most of its data from 18 reports from the National Runners Health Study, as well as the National Running Aging Study, the Copenhagen City Heart Study, and the Aerobic Center Longitudinal Study's Running Report. The authors include exercise all-stars such as Steve Blair, PED, Tim Church, MD, PhD, James O'Keefe, MD, Duck-chul Lee, PhD, and Lavie.
Read the original article at Runner's World
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