Hi guys.
A question about the results on the 2x 8’ FTP test. Actually, the question is about the Avg Hr from those intervals. is it accurate to use it as my Threshold Hr for cycling? I don’t have long intervals (>20’) at full power output yet, since I’m a newbie in the triathlon/cycling 
Thank you all
IMHO 2x8’ FTP test is not good to assess FTP nor threshold HR. It will give you too high numbers.
For example on a 2x8 min test knowing myself I think I will put 290ish watts @ 165 bpm
But my FTP is around 240 these days and my SV2 threshold HR for cycling is 155ish
RHR 42 Max HR 180 62 kg 40 yo
Do this 20 minute test is better (not perfect at all) to assess FTP, or even better do a 60 minute test and a 20 min test. Then you will have your own ratio between these two tests.
If you have got latest garmin devices I find them quite good at estimating VO2max, FTP and threshold HR (comparison with lab test for myself) (I think there will be some comment on this doh !)
Well, I actually agree on that 
There will always be debate and it can go either way (too high, too low), but remember that a lab test a) is expensive and b) result gives you a measure for that particular day and may differ a week after.
You use your Garmin every day and it will be better at monitoring and calculating your exercises and fitness parameters throughout the season. It’s also not bad at estimating your training effectiveness - in fact, better than what I see here or on Strava.
In my own experience, the Garmin results are within error margin range of lab results.
Hey guys, thanks for your answers.
I could not find a threshold HR estimation on garmin connect for cycling, only for running.
Also, I’ve not doing continuous long hard efforts (>20 minutes) in a while since my last race (10k run - 03:53/km and 183 bpm average) was on August 2019. Since then, I’ve been using 183 bpm as my LTHR for running, 110% of it as my maximum (201 bpm), 173 bpm (10 bpm less) LTHR for cycling. The threshold pace I’m using currently is also the same value of this last race.
Last months garmin connect have been estimating my running LTHR to be around 177 bpm at a pace of 4:27 based on training paces and HR.
What do you guys think?
BR
Which Garmin device is that? I believe my Fēnix 5 did both, but I now and Edge 530 and I’m not sure.
It depends on the athlete, but as a sort of rule of thumb, you may assume that your cycling LTHR is about 10 beats lower than for running.
Based on that 177 you get for running, it would be 167-ish for cycling.
Forerunner 945…
But the 177 seems weird since I’ve done an effort that guided me to 183 on the past, as I’ve mentioned. Unfortunately, my garmin device was a forerunner 235 back then and garmin connect didn’t save it’s LTHR information. I’m using the 945 for a couple months and the only race I’ve done with it wasn’t at full throttle.
With your 945 you can do a lactate threshold test running with your watch and a HR strap, just launch run, training, guided threshold test and follow the watch instructions
You will get your running threshold HR, then you can use the rule of thumb for determining cycling LTHR or also do the garmin FTP guided test or a 20 minutes or a 60 minutes test