Bests & Worsts Reviews from Amazon

After trying two of the new models (the 24) and one of the old one, I can say that they do NOT replace a heart rate monitor chest strap AT ALL. These arm worn optical HRMs have the exact same limitations as do the wrist worn ones on any fitness tracking watch. They only deliver good results for moderate levels of activity in an upright running position. Vigorous sprinting, High Intensity Interval training, any sort of bodyweight activity on the ground like burpees, push ups and animal flow and you will have all sorts of connection and performance issues. This is STRICTLY for runners and not even for sprinters. ANY vigorous arm movement causes the monitor to either lose connection or report ridiculously low readings (such as 40 or 50 while running 40 yard sprint intervals or hill sprints). Do not be fooled by marketing. It WILL NOT replace your reliable chest strap. I have spend MONTHS trying to make this work. And since I gave up in exasperation and allowed the Amazon return date to pass by, neither the vendor nor Garmin will give me a refund. It's a fine unit that does perform better than the optical HRM on my Garmin devices but ONLY for upright activities that do not involve vigorous arm movements. So if you are doing HIIT or athletic training (other than straight running) forget about it. Stick with your chest strap. I wanted this to work and I really tried but please save yourself the trauma of the experience and just don't buy this unless you are simply running, jogging or some light jump rope or slow moving weight work.