W’ and CP are constructs and modeling parameters. I agree, they are never going to be accurate down to a T.
Thanks for the explanation. My main motivation on seeing the W’ numbers is to see how many matches I burn and how much I can sustain before I totally burn out during a ride w/ my mates.
All, I’ve a question on using W’bal, how far to “trust” it, and what to learn from it…
I am still relatively new to cycling, first (Gravel) bike 18 month ago, structured training with powermeter (inside and outside) for 9 months now, Roadbike since February, first few races done in the last weeks.
This is all at age 50+ and 80 kg.
I use i.icu to analyze my rides and training progress and generally also to determine FTP and W’bal, generally using its building eFTP/eCP metrics (I am using Morton’s best effort algorithms). For the whole time with powermeter, I have been using FTP according to eFTP and matched that with the W’ from the eCP model… because these are the two higher numbers in my case;-)
Right now i.icu gives me eFTP = 314 W, W’ = 22500 kJ; eCP = 308 W, W’ = 25200 kJ; thus, I set my FTP to 314 W and W’ to 25200 kJ…
These data were just updated from a “best 6 min effort” during a hilly 3:15 h race yesterday, these 6 min were on a first “longer climb” ~1 h into the race.
Still despite already fudging the data and using the “after-race data to analyze the race itself”, at this very “climb” I get a W’bal down to -3 kJ.
And this is a recurring pattern: I set FTP + W’ to the larger individual values from eFTP and eCP and still run into W’bal < 0 for hard efforts. I have previously adjusted W’ accordingly, to avoid going negative, as I understand that the estimates are not super accurate;-)
However, what I am wondering about is if I should (partly) compensate these negative W’bal values by increasing the FTP for training/analysis, which would, of course, also mitigate the “negative W’bal” problem. Would this lead to a better FTP estimate and thus better training?
All thoughts and suggestions welcome:-)
Btw. yesterdays race went pretty well;-)
Check your power duration curve. Do you have values below that of what the model predicts at a given duration? If so, look at the duration and consider during some future ride or workout, doing a max effort for that duration. This should help to update aka feed the model.
For example, I don’t do short efforts or intervals very often. As a result, my 1min power is 51W lower than what the model predicts. I also know that I can actually do much more than what the model predicts if I do a 1min max effort. If I do the 1min max effort, the model will update and likely give me new eFTP, eCP, and/or W’ values.
Thanks.
Which would mean I have to do some max. efforts in the 75–150 s range and also for 12+ min…
Exactly these long steady max. efforts is it that I am trying to avoid;-)
And the short ones don’t seem to be used in the modeling – in settings there is a “min duration for estimating eFTP” with a default of 5 min and on the power page it says that the algorithm “requires one max effort between 180 s and 30 min”.
I am happy with being a little “personal” about it and to use my own “natural intelligence” (in contrast to artificial intelligence;-) in the analysis… and thus looking for some more background on what might be going on here with my FTP-W’ relationship;-)
In a recent podcast I’d also learned about using both AP and NP from hard rides, e.g., races, to (manually) estimate FTP. @david , it would be great to get an additional power- curve using NPs for the different durations on the i.icu/power page!
Hi, is the W’ bal graph for an activity calculated using user inputted FTP or eFTP?
It uses user inputted FTP.
Alright, thanks!
Hi. Consistent with many on this thread I am trying to fine tune my w’. Sounds like come variability and imprecision is expected. When I look at my interval.icu activity w’ graphs it looks like it’s working correctly. I recently changed to Morton 3p, because I have a lot of regular 5s, 3min, 12min etc. full efforts. This gives me a value of 15782 which is a bit lower than the default eFTP at 17425. On my garmin edge though and using the w’ prime app someone mentioned above, I am getting really deep negative values. Like -30% at max efforts. Why is there a disconnect with the intervals.icu graph for the activity and what my garmin shows? I assume it’s something to do with skiba and the other one and I should just try the other one?
I somehow forgot a plot that I discovered some years ago while using Golden Cheetah regarding the CP/W’ model.
But it is a very interesting plot and probably quite easy to implement for @david.
Might be worth reviving this:
Thats a very interesting plot and article. Tx.
At some point soon I will have to “pause” implementing complicated stuff and build some new charts (quadrant analysis and this one spring to mind). I like building charts.
Hey Robin, it is important to have the ftp and W’ both obtained from the same calculation, if you want to use the eFTP then take the one that comes with the eFTP. Both metrics are related and when one is higher the other one is lower and the other way around. Try using 17425 with eFTP or 15782 with morton’s CP. The other way would be to increase W’ it so that the -30% equals 0%. But I would try the first option first.
My eFTP and CP are showing as 257 and 258 respectively, yet the default vs the morton’s 3 parameter w’ are a ways off. However, your point is taken to use the coinciding numbers. Where I am still confused is what to input on my garmin edge. Do I use the eFTP w’ amount of 17425 or the morton’s 3 parameter value of 15782. And secondly, do I use the skiba differential or the integral? Appreciate your help.
The difference between the 2 values for W’ is about 10 %. For this parameter, that’s to be considered ‘normal’…
That may sound ridiculous, but given the fact that there are 2 models (integral/differential), with both an average value for an unknown recovery parameter and the 1001 possible ways to deplete W’, that’s just what it is.
Some are better of with the integral model and others with the differential one. If your pattern for depleting W’ is somewhat recurring, you will have better results. If it is random, there will be more spread. Some more debate around that here:
Read the article posted a little higher and you will understand that there are conditions in which you are unable to use all W’ available.
@MedTechCD Excellent points…I find the go all out to exhaustion challenging to determine. I simply try to stay at consistently stay at correct above threshold power level % for the interval. For HIIT intervals above FTP/CP a lot obviousy also depends also on the effort to rest ratio (which I assume is related to Tau time constant recharge for W’ although it is likely to be non-linear? I have heard two expert anecdotal comments for VO2max intervals I thought I might share.
- I once heard Hunter Allen comment on a -% threshold (i.e. subsequent intervals % vs initial interval) that he used to indicate your workout was no longer as effective and you should stop the interval session. I can’t remember the exact value but thought it was -20%? Has anyone else seen this type of guide.
- For VO2max interval effort/rest ratios, I have heard some various opinions on optimal effort/rest ratio. I did hear Peter Attia comment on a recent podcast the strives for 4min intervals at 1 to 1 Effort /Rest interval. (there is also question regarding whether the rest should be complete rest or some active power…but that goes deeper down rabbit hole!)
It a 10% drop. He mentions it here.
Optimal is dependent on how quickly you recover. 1:1 is generally prescribed as ideal, but if you need 30 seconds longer to recover, which means you can get a consistent average power across all intervals (first to let), then that’s okay too.
I’ll share some links to podcasts that touch on VO2, a little later.
Some links to a few podcasts:
-
Featuring Hunter Allen
How to Make VO2 Max and Threshold Workouts Work for You - with Hunter Allen - Fast Talk Laboratories -
Time at VO2max
Time at VO2max: An Important Metric You Probably Haven’t Heard Of - Fast Talk Laboratories -
Featuring Dr Stephen Sieler
Are Your Interval Workouts Effective?—with Dr. Stephen Seiler - Fast Talk Laboratories -
Favourite workouts (featuring a few good experts)
Ironic that VO2 workouts are listed as favourite workouts; I enjoy them too out of all the “hard” workouts, however nothing beats just riding a bike.
Favorite Workouts—Race Season Edition! - Fast Talk Laboratories -
Wahoo have the 4DP test, of which MAP would be similar to VO2
https://the-knowledge-by-wahoo-sports-science.simplecast.com/episodes/episode-63-understanding-4dp-metrics-part-3-maximal-aerobic-power -
Empirical Cycling - 10-min tips on FTp and VO2
Stream episode Ten Minute Tips #28: FTP and VO2max Thoughts and Listener Questions by Empirical Cycling Podcast podcast | Listen online for free on SoundCloud
I have missed quiet a few, but these ones a fresh in my memory.
I’ve just added the W’ plot from Veloclinic into the power page of activity. However, I noticed a peculiar behavior. The simple use of MMP hides part of the forest. To be more explicit, on an activity with repeated short interval efforts, such as 20/40 or 30/30, W’bal falls below 0.
However, on the W’ plot from Veloclinic, because the rest periods didn’t improve the MMP (cp curve of the activity is in black, cp curve for the last 84 days in blue), the information on the ability to repeat intense efforts doesn’t appear.
It’s therefore a graph that I find very interesting, but like all data, it needs to be coupled with a more detailed analysis of activity.
Hola David, cuando pongo en la actividad para poder ver el grafico de W´ el grafico nunca aparece, como puedo hacer? Gracias