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:
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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.
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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.
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@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.
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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.
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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.
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Hola David, cuando pongo en la actividad para poder ver el grafico de W´ el grafico nunca aparece, como puedo hacer? Gracias
After reading lots of “stuff” on W’Bal and CP I think that this is the easiest answer….
All of the mathematical models of W’Bal (2 or 3 point models) are inaccurate because they assume everyone is the same.
The best way to gauge YOUR W’Bal is to get a relatively accurate FTP and then go all out on a ride - review your W’Bal after the all out effort and adjust your W’Bal so that you normalize your value to 0J at your peak depletion.
Does anyone see any issues with that particular method? Other than it isn’t as sexy as a mathematical model 
And even then, if you do multiple hard efforts with some recovery in between, it might still be significantly different compared to one all out effort.
But if you do the same protocol each time you ‘test’, you may be able to extract some useful information.
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Good point, it would have to be an iterative process across many max efforts (naturally some will be long single efforts and others more choppy and repeated efforts), but in the midst of the many data points there should ideally be a linear trend upwards of an increasing W’Bal.
In fact, I was just looking if I could look at my max W’Bal depletion per activity and did not see an option for W’Bal depletion - can that be a metric to add in the future? I’d love to see how that value changes overtime
For example, this activity would have shown a max depletion of 23.8kJ (17kJ - (-6.8kJ))
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Hahaha wow the sad part is that I looked! 
Thanks for pointing it out to me
Is there a reason why my W’ Balance would empty on a max 6 minute effort (I set the W’ Balance value based on this, 25.5k I think) and it goes to 0 at the end of my 6 minute test.
Doing Vo2 sessions today, 3x8 and on none of them do I even get close to 0, even though at the end of the 3rd set I am literally done. I don’t think I could have done much more work above FTP, certainly not the 13k that I supposedly still have left in the tank.
Quickly checked last year, same story, did a 6 minute test, where I deplete about 23.4k (a bit higher but it’s 23.4k if I set FTP to eFTP which is slightly higher so I went with that for that exercise) and the test ends at 0. I did some 8x3 the week before and even though I know I am always done at the end of those, the last set ends with supposedly 13k still left (the 13k both times may be coincidence, I also rounded a bit). How is that possible? Surely one should be at 0 if one can’t go above FTP anymore.
It’s worth remembering that you are dealing with two models here, both of which may not be great at representing your physiology:
(1) The Critical Power / W’ model from which you have got some values that represent your current fitness level. You haven’t stated how you determined your FTP, but you have said you have determined your W’ from just one effort - this may not be the best way to determine your W’. There is quite a lot of academic literature out there looking at how an individual’s CP / W’ can vary significantly by choice of defining tests. If you want a read, here is one, admittedly quite long!
(2) The W’ reconstitution model, which has been discussed in a number of threads (here’s one) and is not tuned to your actual recovery abilities which likely differ to the standard assumptions.
As for what to do with that information, for me it depends on what you want to use W’ (balance) for. If it is just for tracking your fitness / performance over time, and if you are testing in a consistent manner, I don’t think it matters if you see significant variance from W’=0 when you are actually completely spent from above threshold work. If you want to use it to help gauge how much you should have left in the tank as during particular types of rides, you may want to look at different protocols for determining W’ (and CP). That could be different tests (duration, quantity, etc), doing your 6 minute effort after you have already done a certain amount of work, or something else.
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Thank you, a lot of information.
Yes I suppose my aim was to use it to see if I get the maximum out of myself, and if certain Vo2 protocols do this better than others.
Yes, I think my recovery abilities are probably lower than what is assumed. And if I take the FTP/W’ values from Golden Cheetah, 243 and 21.1k, then yes the 6 minute max effort goes to -3.3, and the 3x8 doesn’t go near 0, but the 30/15s look pretty good, very good even if the recovery is over-estimated by a few 1000.
But you are right, it shouldn’t be necessary to get it to 0, but as long as I do it consistently, I can still compare across efforts.
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