BT 3 hours into a ride⊠great work @davesans 
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You can see just how that power developed that the system is going to have a very hard time extracting a valid signature for that effort - unfortunately short, peaky efforts arenât extracted very well by the system.
You get to ride outside, lucky you!! Nice work on the BT too 
!
Here you go Scott - this was a tough hour not that long after starting to use Xert earlier this year:
Soon after I settled on GC Specialist and am in the build phase now so lots of endurance rides which donât really drop my MPA at all.
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Curious to get @ManofSteeleâs perspective but looks to me like you didnât necessarily reach a point of failure in this one i.e. you were able to follow a (super tough) workout in ERG mode?
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Hi @SimontheBike, great effort on this activity! Was this your own workout, or one you did elsewhere?
Now you might have a extraordinary capacity to suffer in agony, but whatâs more likely the case is that your current fitness signature in Xert is under-estimating your âtrueâ fitness signature. As @wescaine mentioned, I suspect that this activity doesnât accurately capture your true max. A difficulty score of 290 is INSANE! Dr. Stephen Cheung, our Chief Sports Scientist here at Xert is known for being able to sustain a pretty high difficulty score, but even he is often forced to back off around a 200 DS. In my own data, I know that hitting a DS of ~165 is about my maximum tolerable limit - Iâm simply unable to continue riding hard and am typically (mentally) forced to back down.
If you open this activity in Xert and go to âAdvanced MPAâ and bump up your Threshold Power by ~5W, I suspect youâd see a more accurate representation of the Difficulty Score, XSS, etc.
Looking back to dig into that activity and I cannot even find it now, which is really odd. I suspect it was early on when I got started in Xert and hereâs another one from that time period, which was a Zwift Academy Road Race, so I was pushing it, but Iâm sure youâre right about it being the weakness of the signature database at that point causing the crazy XSS etc
This one is more recent, again from a Zwift event (my Xert-determined rides are all Endurance-focused currently) where I went for a quick sprint after finishing.
Just picking up on the XSS comment though, this is my highest steady grind - and no breakthroughs!
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Tour de Zwift Stage 5 Volcano Afterparty. Found a group a cruised at an endurance pace for the flat portion, then went full gas on the KOM. Started a bit too hard but push to the end got a breakthrough. Fun ride.
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Does this mean you rely on Zwift events for BTs and do not perform BT workouts on occasion? By that I mean purposely select one from the library after a rest day or when you are feeling particularly fresh. XATA wonât recommend this but does warn you when your signature has become stale (time to try for a BT).
Zwift events are a possible source for a BT, but BT workouts are expressly designed to sample your power curve, draw down MPA, and generate a BT. Not guaranteed of course, but more reliable than an event or lively group ride. 
Search the workout library for âbreakthroughâ then read description for instructions. You can also view details in Workout Designer to see how each one is setup. Most should be ridden in slope mode but at least one works in Auto mode.
Try them all over time and see which one you like the best or is it worst? 
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Itâs amazing how I could already infer that just from looking at your MPA chart! One of the quick lessons that Xert can teach is properly pacing an effort - itâs amazing how much a short little burst near the start of an effort can negatively impact your ability to generate power many minutes later!
Congrats on the BT though!
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Hereâs mine from a lunch ride today:
Have been on âNo decay TL matchedâ for ages (last BT start of November) and this suggests my signature based on Xert estimates wasnât too far out at all.
I did the Xert BT test number 3 without trainer control, just to have a little structure to it⊠but shortened the rest between blocks as I was getting bored!
I do wonder if HIE is a bit overstated, noting I couldnât quite get MPA down in the second block⊠could also be fatigue (my TL is only in the 40s which could affect recovery from all-out efforts), shortening the rest beforehand (though MPA had recovered), or bad technique sprinting indoors (including gear selection / cadence) I guess.
Iâve been lazy over Christmas and started in January with some endurance workout but they seemed to easy so I went for a breakthrough. I did Xert BT test number 3 but tried to have slightly higher power. Iâm having a hard time to do high power output on the trainer, but the 5 minute interval worked.
It seems iâm having the same issue as @wescaine as HIE seems quite high now (higher than last summer) so iâm not quite sure about itâŠ
The parameters of the signature that get changed are a function of how the BT was generated. Typically, these short âPull MPA down in a hurryâ will put more emphasis on changes in HIE, since HIE is the largest contributor to work performed around the 30s-3 min mark.
OK, but MPA is actually drawn over 10 minutes plus when you look at the intervals? Or does each 25 second ârestâ between intervals cause some kind of reset? Ignoring the small recovery of MPA, would simply continuing the ramp without those short breaks give a very different signature?
Yeah, it seems the shorter intervals before werenât high enought to pull the MPA down, I just did it in the 5 MMP interval. I just wanted to look at the workout again and noticed itâs not a gold breakthrough anymore and calculated different stats. I didnât change any parameters, how can that happen?
I guess I was looking more at @fantasticfuhr 's BT when I made that comment. His change in HIE was dramatically higher than yours. Expected given the visual difference between the two BTâs.
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Hi ridgerider2, I hadnât done any specific BT workouts until today when I did the Version 3 Fitness test after a day off the bike and gave it my all!
Amazing to watch that MPA come down during the first repeated efforts but the final segment of the workout had me grinding to a halt as I hadnât got my cadence up before the ERG leapt up - to be fair I couldnât maintain if for more than a few seconds when Xert dropped the demand for me either - I was a gonna! Gave it a while to recover on the cool down and then a quick few seconds maxxing it during the cool down which had turned ERG off.
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Iâm following this topic some time now, really nice to see everyoneâs BT and efforts 
Here is my BT of today:
I was on a groupride on RGT (a very nice online platform to ride, if you want some visual stimulus while doing an indoor ride/training). I wasnât really looking to get a breakthrough, but I found myself in a nice group and decided to stick with them. I got dropped 1 time, so in my effort to sprint back to the group I made a Breakthrough 
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Nice jump in sig values on that one. Subsequent workouts are going to be tougher with the new TP. 
It takes practice to learn the ins/outs of the BT workouts. First couple times I blew the efforts or hit a wall unprepared.
It amazes me how the Xert model can predict what you can and cannot do. You look at the workout think âOh, I can do that. No problemâ. Then when it hits youâre suddenly âUgh!! Cancel that thought.â Better luck next time.
Yes, itâs an amazingly accurate and dynamic system. I think this workout demonstrated to me the downside of pushing to the limit in ERG-mode - if you donât raise your cadence going into the hardest efforts the system drives up the torque requirement, which you canât meet, so it asks for more! Even though it (uniquely I think) slackens off pretty quickly the momentum is hard to build-up again. Slope mode I guess it better/best?