how to delete an activity like it was never ever ever done!

Unfortunately, most of the FirstBeat analytics are calculated right on the watch when you save the activity.  The watch doesn't have a "guest" mode that I am aware of to allow you to loan it to someone and let them save without it affecting your stats.

You can delete the activity itself, but it will not delete the impact of that activity on your analytics.

The good news is that one non-representative activity won't have a long term impact and should fall out within a week or less.  I've even had this personally if I forgot my heart rate strap and went on a run using the optical HR and, not paying attention to it, had a long period of the run with cadence lock making it appear that I ran for an hour in zone 5.  It will cause the most pain for you for the next couple of days if you use the recommended workouts.

You can delete the run from Garmin Connect but I'm pretty sure you can't undo the effects on any training-related stats.

I think you just have to wait for your stats to go back to normal. Shouldn't take more than a few days.

This is very dumb.

I paid for two premium watches and can't use them with someone else in guest mode?

This is a tool (my tool), Please someone at garmin get this guest option working.

My new max heart rate has been updated to 200 mHR? because my 10 year old son ran at 190 bpm for 30 minutes.

Now all my stats are broken.

The only way I can see lending a watch is having user profiles like on a computer. 

But we should have an option to undue something.

Imagine starting a watch with a bad sensor...

I can't guarantee it would work, but I believe that if your son discarded instead of saving at the end then it would not impact any of the metrics.  Of course, you/he would not have a FIT file for the activity either, but maybe you don't care about that.

You could have turned off lactate threshold and HR auto update before loaning out your watch. When my wife rides with me she uses my F7 all the time but you have to make sure you discard the activity and not save it, once you save it will write the fit file.

It is possible to grab the file before saving/discarding.

ok so since its saved the damage is irreversible ?...this is so dumb

ericgottlieb said:

I can't guarantee it would work, but I believe that if your son discarded instead of saving at the end then it would not impact any of the metrics

Actually, I once discarded an activity on a 935, and the recovery time metric still popped up immediately after.

I've also seen some people mention that discarded activities affect training status, training load, recovery time, etc.:

https://forums.garmin.com/sports-fitness/running-multisport/f/forerunner-645-645-m/280009/discarded-activity-and-training-load

Lately I've been letting my son borrow my watch. He discards the activities, but it sure seems like this is affecting training status, training load, recovery time, etc. Any way to fix this?

https://forums.garmin.com/sports-fitness/cycling/f/edge-830/171065/discarded-rides-will-be-counted-by-training-load

when you discard a short ride e.g. 5min because you deteced there is something wrong, missing sensor or so, this activity will be counted by Training Load, but you see this wrong calculation only with active Physio True Up!

www.trainerroad.com/.../26

Hmm, I’ve just checked my records for the 530 and it looks like [training load] is being saved despite always discarding the ride:

Patk said:

The only way I can see lending a watch is having user profiles like on a computer. 

IMO, Garmin will never implement that for (probably) the same reason (I'm guessing) Apple doesn't do it for iPads: they want each user to buy a separate device.

It would be nice tho.