I started using Xert this week and uploaded my last 3 months of training data (max allowed during the trial). I was a bit skeptical of both the initial fitness signature and the power curve based on my best efforts from the end of last season. I figured I would let things ride for the first workout and see if I need to adjust, and maybe go for a breakthrough and see what the updated values worked out to be.
Well I finished the first workout and acheived the breakthrough. This tweaked my fitness signature a little but did not fundamentally change it. Here is where I currently stand:
I was skeptical of the 5m power estimate as I had been doing 5x5x6 intervals two weeks prior and was at 290w for my best effort from those. I was also pretty skeptical of the LTP number as my understading was this should be around LT1 or lower Z3 in a 5 zone model. For me this is low Z2, I estimate my Z2 ends around 170W.
I looked into the power curve and input some of my PB values from the end of last season. While not 100% accurate for my current fitness they are within 5-10% and what I had off-hand without digging through my power data. Anyway, it came up with the red curve which is much more inline with what I expect, especially given my actual measured power curve from the same time frame.
So circling back to the workout I completed, I was reccommended around XSS split 114|23|3. As mentioned, I got a breakthrough and while it was not an easy workout I never felt at risk of not completing it. Here is the power curve from where I accumulated the bulk of my XSS high:
So given all this information I wanted to mock up a few interval workouts that I am more familiar with so I went back to the 5x5x6 workouts I had done 2 weeks ago. With my current signature I would get nowhere near my XSS high target for the day and I would say those were significantly more difficult for me to complete than this workout. Like at least 2-3/10 RPE more.
So I how do I start to make sense of this all? I completed this workout with what I think to be an incorrect fitness signature, yet more difficult workouts I have done (in the RPE sense) wouldn’t have some close to fullfilling the same XSS target as this workout. I can force the fitness signature to be inline with the calculated power curve but I’m not sure that’s a long term solution. Would that even be beneficial or should I continue on with this signature because I can complete the work even if only with specific interval types?
your signature looks like a strong sprinter ones. Huge legs. 1441 Peak and 35.5 HiE is really very strong, but your aerobics are not as much. That is the tradeoff. LTP=TP-2.5*HiE. Sprinters have even lower Zone2 percentage wise. Your 5 min-power in the signature is a “perfect one timer”, not a 5x5 one.
It is quite possible that 5x5@120% TP is something that is too easy for you while 3h@150W will grind you to exhaustion.
Your HIE looks a bit high, also considering the guidance here… could be worth using your other manual signature?
what happens if you use that signature in your latest breakthrough? if you’re happy with it, you can save / lock it in that activity. If it’s still causing a big breakthrough you can first enter the parameters from your manual signature estimate, and then extract and see what comes out… save when happy. This also assumes that you did max efforts… did you?
Am not sure what 5x5x6 is (5 lots of 5x6m max efforts doesn’t seem reasonable to me)… but if it’s something like 5 (or 6) x 5 (or 6) min max efforts, while they are above TP, they are not as strongly focused on HIE (as you will need to get to a 23 High XSS)… so it’s a different focus than what you were recommended… you will need higher intensity (but more reps and shorter) to get a very high high XSS load. And you shouldn’t consider high XSS in isolation - it’s the ratio to low XSS (and peak XSS) which is important.
Longer intervals often have a higher RPE than repeated short intervals… just think about long threshold intervals which have 0 high XSS but can be very difficult.
TLDR: Xert’s power curve will almost always sit above your historical bests. It’s optimistically showing what you could theoretically achieve based purely on your 3 signature parameters. In practice, achieving those efforts (especially in the sub-3 min range) is challenging due to pacing, correct cadence/gearing, having adequate resistance, etc.
You’ll notice as you play with the Workout Designer the MPA graph and Difficulty Score (shaded portion of chart) indicate how hard the workout is going to be based on your signature.
Dynamic intervals can be defined for both work and rest intervals ensuring a specific recovery level between efforts.
You can also import your favorite %FTP workouts and SMARTify them during import. Import Workouts into Xert (ERG/MRC/ZWO) + SMART Conversion Settings – Knowledgebase
Really appreciate the quality reponse, it is very helpful
That manual signature estimate was max efforts yes. I took your advice and I think my fitness signature and power curve look much more reasonable. Power curve looks potentially acheivable with perfect pacing, or maybe in erg mode. 5x5x6 was intended to mean 5min work, 5min rest, 6 repeats, apologies I should have specified. I was giving close to maximum effort for each interval and they stablised around 265W for the third onwards. To that end, I created the same workout with the updated fitness signature and got 13.5 high xss and 133.0 low xss. Based on what you said about high xss and based on what I can find about HIE, would it be accurate to say that it is analogous (if not exactly equal) to anearobic energy capacity? If so, and expending this is required to get high xss load I think the whole equation makes more sense.
Understood, I think with the signature calculated bast on best efforts that is more or less what I get. Something I could maybe achieve on the perfect day in the perfect scenario.
Yes, similar to W’ but I think not exactly equal. It’s a detail, and the Xert team can explain better than me, but at least when it comes to modeled power curves, the CP / W’ model assumes that in a max effort you’ve exhausted W’ and so can theoretically only hold CP… while in Xert when you fail e.g. a 5 min effort, it just means you can’t hold that power level (eg 120% or whatever it is) anymore, but still could ride above TP for a bit…by definition of a BT your power is equal to your MPA / max power available of 120% at that point in time (but declining rapidly).
