My Garmin watch has an app that converts distance and heart rate into a suffering score. This app is the only reason I finally invested in a heart rate monitor. Plastic is also quite comfortable under a sports bra. I actually came back from a run, stretched and forgot I was wearing it for the 2 hours it took me to cook and eat dinner. I only noticed that when I was taking a shower. I haven't compared it to other devices so I can't guarantee accuracy but based on old school testing it seems perfect. The additional data it sends to the Garmin Connect app can also be overlaid with time, distance and elevation. I'm a nerd so I like to have extra stats to look at.
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