I run with a Garmin forerunner 35. I know wrist hr is typically inaccurate, but in which direcion? My typical easy day heart rate is between 162-170. This is almost certainly aerobic. BUT, 170 seems pretty high compared to most people's top of Z2. I am curious if my heart rate is actually quite a bit lower than this. I think this may be the case for 3 reasons. 1. Often when I compare my pulse (just by using my fingers against my wrist) it is much lower than the Garmin wrist heart rate. Often up to 10 bpm difference. 2. Even when I increase slightly over 170, it still feels very easy and I can still sustain this heart for 90+ mins. According to Maffetone and most basic heart rate zone calculators based on age/ max heart rate my top end of Z2 should be around 165-170. 3. I can also sustain over 170 bpm (according to Garmin wrist HR) by nose breathing without feeling short of breath or anything. This all leads me to believe that either my Z3 is so overdeveloped that it's just crazy. Or the wrist heart rate is just always a lot higher than my actual heart rate. This is confusing because I've seen tons of peoplle saying that Garmin wrist HR underestimates heart rate. I am also strongly considering buying a heart rate strap, is this worth it? Discus.