Fenix5 HR accuracy issue in cardio activity

My Scosche Rythym + (Valencel sensor I believe) proves this untrue. It is dead on accurate (if only 1/2 second timing difference) with Polar or Garmin heart rate straps

This is not my experience of the Scosche Rythm+, I've tried multiple placement positions all up and down my arms and all are woeful during strength training; better than the Fenix 5 wrist OHR, but still unuseable. The only thing I find that reliably works for strength training (whether lifting weights or functional/bodyweight exercises) or circuit training is a traditional HR strap. But maybe your success with the Scosche is that your skin type works perfectly with OHRs. Therein lies the problem with OHRs, even the best; they are not only sensitive to placement, but many other factors such as skin colour, temperature and ambient light. Whereas a chest strap that has a little water between the strap and skin, seems far more reliable in a much broader range of situations. We all love the convenience of OHRs, but folks really do need to understand their limitations too.

Yes if you want to be pedantic about it.

Since we are discussing the OHR on a wrist watch, on a wrist watch forum, I had assumed a context to the discussion had already been established.

Your point about Garmin and others misleading the public about the usefulness of wrist-based OHR included your opinion, stating-- "where you really need a proper HR chest strap." My point is--that's not true. The Valencell sensor on the Scosche product, with whatever hardware benefits or firmware algorithms it uses produces accurate OHR readings under many conditions by my testing and others I've read--without requiring a chest strap. If you want to keep it on the wrist, the Suunto Spartan Sport, for whatever other flaws, also uses Valencell OHR and has apparently received good ratings for it's OHR performance.

The Scosche Rythm+ does slightly better than the Fenix 5 WHR, when it's placed on my upper arm with the sensor on the outside edge of my biscep.

Just curious and a little offtopic - why the outside of the bicep? I'm very happy with my Scosche but have always worn it on the inisde of the arm above the bicep.

Grove erba

I am mostly a cardio/gym person. Here is what I've noticed.

My Fenix 5s seems pretty darn accurate for cardio classes like Body Combat and Sh'Bam. These are mostly steady state cardio classes, with no huge herky-jerky movements.


The latest Body Combat release has a section with mountain climbers and "sprawls" (damn burpees). These huge broad movements seem to throw my Fenix 5s off. The OHR can't keep up with these full body movements up and down.

It also is completely useless in HIIT classes like Grit. Again, the large arm and full body moves confuse my watch, I think. It does well with HIIT on a stationary bike, however.

Just what I've noticed.

Just curious and a little offtopic - why the outside of the bicep? I'm very happy with my Scosche but have always worn it on the inisde of the arm above the bicep.

I tried many different placements when I first got the Scosche and that happened to be the one that I got the best results with. It works for me but something else may work better for others as peoples' bodies are all different.