Usefulness of Stamina

Did you do it as 6 different activities (6x1h) or as one long activity (pausing or let the timer run)? I guess as 6 different activites.

Is seems the watch thinks you have no Stamina left after 2h. Stamina takes previous activies in consideration. For example, if I do a threshold run and have a Stamina of 35% in the end and then a short while afterwards (10 minutes change of clothes) do a bike session the bike session starts with a Stamina of 35% + whataver Stamina I have recovered from 10 minutes rest.

Have you checked your settings for max HR, threshold HR (or power e.g. FTP) to be accurate? If the HR settings (or FTP) are wrong (including estimated VO2 i assume) also the Stamina calculations will probably be wrong. 

For me Stamina seems to be rather accurate, perhaps it says I have more Stamina left in the tank than what I feel. But then, I haven't used it in a race. Only training and usually you can do it a little bit harder in a race...

Basically the same joke. During a 24h gravel race the stamina indication dropped to zero in 1:35, but, in real life avg speed did not drop at all and there was plenty of real stamina left for final push :)

interesting. I think garmin will imporve this statistic later, especialy on longer, ultra distances. I feel this firmware is in late beta stage for now.

I am curious about more than maraton run or 200Km bike ride. For now i have done only one 130km+gravel ride and it was about ok for me. On start it show 230+km max but after i hit gravel and  a lot of sandy traills it started to decline faster.  Maybe it need stime to calibrate like body battery

On runs it shows about correct max distance which i can achieve when rested and well fueled. I am more curious how it will work when i will be fatigued on start (illnes, bad sleep etc) on with bad nutrition. 

Not very impressed when used for running, that's for sure. I did a full out 15k race and was told I still had 35% stamina at the end (time in line with predictions and VO2Max/HR/TPace all correct). I'm hoping it makes more sense when used with a power meter for road biking and you can actually recover on a bike but not holding my breath ;-)

Real-time stamina offers the most insight in activities where you are really pushing your limits. 

As your stamina approaches zero, you will likely find that your ability to sustain hard efforts is significantly compromised. You may be unable to attack or maintain speed on climbs. You will still, however, likely be comfortable sustaining moderate-intensity efforts slightly below your lactate threshold or FTP provided you still have potential stamina available.

When your potential stamina is depleted, you will probably find maintaining even a moderate-intensity effort is a significant challenge. It doesn’t necessarily mean you won’t be able to put one foot in front of the other but expect to find yourself more focused on simply completing the course than achieving a great result.

What if the insight you get from real-time stamina doesn’t match your own experiences? You’re exhausted, for example, but your device shows you are good to go? Like other advanced performance analytics, the reliability and meaningfulness of real-time stamina improves with how well your device knows you.

The minimum information real-time stamina needs to work is your VO2 max. This requires running with a combination of speed and heart rate data or cycling with both heart rate and power data. You should also ensure that your personal maximum heart rate is set correctly on your device. Setting the wrong maximum heart rate has a cascading effect that negatively impacts the reliability of real-time stamina feedback by compromising VO2 max, lactate threshold/FTP and current intensity assessments.

Following an ideal fueling strategy can also help ensure meaningful real-time stamina, especially for longer activities. Smart nutrition and hydration decisions keep you on track toward your performance potential and prevent you from fatiguing prematurely.

Recording all your activities with your device is the final key to getting the best results from real-time stamina. Not only do stamina levels carry over from one activity to the next, but activity intensity profiles, durations, distances and training load accumulations also are used to enhance the personalization of your real-time stamina feedback beyond your basic fitness metrics. This data is used to model individual fatigue resistance and personal tolerances for aerobic and anaerobic exercise.

From: www.garmin.com/.../