Way back when I was using Suunto devices, I became familiar with Firstbeat Technologies through an app that isn't supported anymore, "Firstbeat Athlete". They have many white papers describing their entire process, and it appears very valid. Not so much for me, a 71 year old overweight guy that's just trying to render out a little of the lard that has accumulated from having a sitting job for-ev-er... but the concept makes sense. I particularly like the "training load" and Recovery times, as I'm wary of my heart, and would like to keep it going in the best shape it can be.

We'll see what happens, but it's for those reasons that for serious activities, I'll strap on my Garmin Fenix 5+ and a chest strap, or possibly an OH1 Polar Optical strap. I have had a Tickr-X for a couple years and absolutely it's my "go to" chest strap, unless I'm on a bike ride, then it's a PowerCal chest strap that determines power as well as heart rate.