With the help of the internet many things that are patently false and based on nothing get repeated and quoted to the point where they are everywhere and all too often taken as true. Case in point: Max heart-rate = 220 minus your age. http://www.webmd.com/fitness-exercis...ate-calculator for just one example.
Yesterday I rode up Wilke Street in Austin. It gets progressively steeper and tops out at well over over a 20% grade as calculated by my GPS. I glanced down at my heart monitor and it said 173. According to the formula my max is 157 as I am 63 years old. My real max is probably more than that as I was only motivated by male testosterone-fueled ego to show my personal trainer who was on the ride with me that I could get to the top without stopping. (He got to the top non-stop also, but, unlike me, had to zig-zag to do it. LOL) If I was riding somewhere with a snarling pit bull nipping at my legs my maximum heart rate would probably be a few more points yet.
I am happy to report that my trainer does NOT have one of those bogus heart-rate charts posted in his gym.
Probably preaching to the choir here.
Don in Austin