Many of you may have heard me discuss this article from the New York Times. I had always felt that my maximum heart rate was much higher than 220 minus my age (the widely accepted formula) so this article was very eye-opening for me. 30/60/90 is based on raising your heart rate to 80-90% of your max heart rate, but if you do not know your true max heart rate you may not be pushing yourself hard enough. This is why I usually use Rate of Perceived Exertion instead, which is when you judge your own exertion on a scale of 1-10. Feel free to comment on this article. I would love to hear your thoughts. Warning...if you are married to your heart rate monitor this might be difficult to read.