Monday, April 22, 2013

How Many Heart Beats Do We Get?
It's a question that every runner is asked at some point: "Aren't you afraid you're using up all your heart beats by exercising so much?"

First of all, for the record, let's just do some simple math. Let's say you're a sedentary dude with a resting pulse of 60. Each day, your heart beats 24*60*60 = 86,400 times. Now let's say you're a real nut who takes up running, and works up until you can go for an hour every day with a pulse of 160 (which is likely an overestimate). As you get fitter, your resting pulse drops to 50. Now, in any given day, your heart beats 23*60*50 + 60*160 = 78,600 times. So in fact, by running, you're saving 7,800 beats every day!

The reason I bring this up is an interesting Danish study just published in the journal Heart. Essentially, they followed 2,800 middle-aged and older men for 16 years, and found that higher resting heart rate at the beginning of the study predicted a greater chance of dying before the end of the study. This is no big surprise -- cardiovascular fitness lowers resting heart rate and also raises life expectancy. But this study had a twist: in addition to asking the subjects how much exercise they got, they also tested their VO2max to get a reliable measure of cardiovascular fitness. Here's the relationship between resting pulse and VO2max:


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