Quote Originally Posted by Yelsel View Post
@Oakleaf -- I'll take up more on heartrate later in a new thread. The short answer is that the Garmin is just using a formula 220-age if you do not set your max heart rate manually; so you haven't necessarily dropped your max heart rate. Your Garmin has no clue what your maximum heart rate actually is, and is just merrily assigning you one and decreasing it every year by rote.
No, it isn't 220-age. You have to do a certain number of all-out anaerobic efforts, and then it calculates your LT based on the point where your speed increases but your HR doesn't any more. I'm giving my max based on the highest I ever see on a hot day on about the fourth or fifth all-out-sprint interval, when I'm deep in oxygen debt but not too fatigued to push as hard as I can. I'm figuring that's my max. I'm not sure how it calculates the start of zone 2, but as I said, both the LT and the start of zone 2 jibe really well with how I feel. There's 95 BPM between my RHR and the start of zone 2, as auto-calculated by the Garmin....

Unless maybe I'm 32 years old and somebody forgot to tell me about the last almost-18 years.