Disappointing first day with the Venu. (HR during a bike ride)

HR during a bike ride is never very good because of the trembling when you hold the bar. It's more reliable when running or doing other sports. I believe this is just physics and there is no way around. You have a strap exactly for that reason. Fitting the watch tighter might help, but I don't think this is so unexpected.

What I dislike much more is that there are no courses on Vivoactive/Venu, and there is no Komoot or native Google Maps app. Sleep tracking and pulse ox are horrible, and I can't adjust the volume of my Bluetooth headphones. In short: the Forerunner 245 seems to be a better smartwatch since you don't have music you can't play, and the navigation properties are better. It only looks slightly less sophisticated, unless you really favour the AMOLED screen, which is understandable.

If you don't activate a cycling activity on the watch, your wrist HR will stay in a passive or low power mode for the optical HR measurement, which just assumes you going about your normal routine. There is no way it'll give accurate readings in this mode during a cycle...

For activities, the watch uses a high power mode, and then it uses different algorithms for different activities to filter out noise and erroneous readings. Even with said algorithms, optical HR readings are not always very accurate for activities like cycling outdoors. 

Cheers for that, makes a bit more sense.

I'll try it on the next outing and see if it tracks in a similar fashion to the chest strap.

like 7956961 commented. Usually during riding your bike your wrist is bended. Therefore the blood circulation is somewhat disturbed and then the optical heart rate sensor is less good. If you want a better optical HR for bike rides you can pair on of those flexible HR bands (like Polar OH1 or Wahoo tickr) and put it on you upper arm for example.

So tried it again today starting the cycling activity with some optimism.

I'm aware wrist based HR isn't accurate but this is too much of a difference and renders it useless. 

Venu:

Chest strap:

I had a Huawei GT2 that actually tracked my chest strap pretty accurately but returned it because of the lack of Strava integration and that it doesn't automatically pause mid ride if I stopped.

At twice the price i was expecting much better from the Garmin.

Its going back for a refund!

Oh dear, that looks really bad. But something seems to be wrong with the watch or something else. I have never seen such bad measurements from the Venu. I know that the watch sometimes measures strange peaks in the heart rate, but overall it is quite ok. Also with interval training. You can see it here for example for running and intervall trainings:

Venu review gadget.fitness (measured against Polar H10 chest strap)

Venu review dcrainmaker (measured against Garmin HRM-DUAL chest strap)

Comparing a chest strap to wrist hr has to be the most "Garmin forums" comparison to do. It makes no sense. There's a reason why you buy a chest strap. Please inform yourself, checkout DCRainmaker, he explains with great details how some challenging situations definitely require a chest strap. 

I have "informed" myself by reading DCRainmaker's review of the Venu, prior to purcahse, and if you look at the HR tracking compared to a chest strap it looks pretty good in his findings.

This is not what i experienced yesterday on a 3 hour ride where the average HR was out by a massive 50+bpm.

I'm not expecting it to track exactly but simply in the same ball park.

With all due respect, but I haven't heard a single reviewer say "yeah this wrist based OHR can definitely replace a chest strap while on a bike".

If you can judge a device from using it once, then I wish you the best luck in finding a device that fits you.

I'm not expecting it to replace a chest strap, just that it should be close or at least follow the elevations and drops in HR.

And yes first impressions count in my view, although this was the second ride.

When they're that bad they leave an impression.

Like i said earlier the cheaper Huawei GT2 tracked very well, on the first outing but unfortunately it lacked in other important (to me) areas.