How much should you run each week for optimal health benefits? Apparently between 10 to 15 miles per week, according to doctors and researchers who presented at the recent annual meeting of the American College of Sports Medicine. Perhaps to a lot of people that seems like a high figure, something they wouldn't really be in fear of surpassing (who has time to run more than two miles a day every day?) – but for some "extreme exercise" afficionados, this might be a tough pill to swallow.
It all has to do with how this intense form of exercise affects our heart muscles. You see, when you're sitting at home exercising your fingers on your iPad or DVR your heart pumps 5 quarts of blood per minute. But, when you're out being physically active and running up hills or pushing yourself, your blood increases the rate it pumps blood to 35 or 40 quarts per minute.
According to cardiologist James O'Keefe, this type of exercise for hours and hours has the potential to do some serious harm. He studied marathoners, ultra-marathoners, triathletes, and other people who do long-distances bike races. He found that the pressure those athletes put on their heart causes muscle fibers to tear.
When these muscle fibers tear the scientists found an increase in the enzyme troponin, which signals damage to the heart and is something doctors look for when they suspect a heart attack.
If you're in the middle of training for your first and only marathon, you can probably keep going, as it appears the damage only results from long-term exercise at these levels. My wife will probably read this blog and say I'm just coming up with an excuse to not run another marathon with her (we finished Detroit's 2010 marathon together, well, she finished way ahead of me and waited patiently). So if that's you, keep on going, because this once in a lifetime challenge won't be likely to harm you.
Basically, the doctors have concluded that moderate levels of exercise certainly increase longevity – sometimes by as much as 7 years as non-active individuals. But there is definitely a limit to the benefits of long-term long distance training. Some of the findings suggest that after a while your body starts to regress and you love the benefits that you started to accumulate.
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