Late to the discussion but saw this popup on my feed.
The question “is it useful” is the central question with any variable.
My personal experience has been - yes. I do a lot of Zwift racing and we know all Zwift races are hard, fast start. Often I have video recordings of the full race. In a recent race, I fell apart after the first 7 minutes from a fast B group on the most sadistic course made - Innsbruck KOM. The data in intervals.icu for W’ showed 0 for W’bal at the start of the 7th minute, meaning from 0-7 minutes, it was all downhill in terms of physiology. The video was nice because I could correlate with the facial expression, the in-game dramatics and everything
The races are not going to favor my physiology, but perhaps I can try to challenge the body to be better prepared for these efforts. I calculated the rate of fall in W’bal = 1.85 KJ/min. Perhaps the HIIT days in my training can focus on fast start type events that expend half of this rate to start out in an interval blocks of 3-4 minutes and then prolong the interval as the fitness increases. This workout might have several minutes of active rest breaks. I can even try manipulating the active recovery break durations by crunching them down.
Those were my thoughts on how I would apply this to my specific situation.
For long distance triathlon, I’m not sure focusing on the W’ aspect will help but sprint triathlons/duathlons often have fast starts.
DISCLAIMER
It is one thing to say I had nothing left because my W’ bal reduced to 0 and another thing to actually verify if that is indeed the case from a physiological point of view. Current understanding is that we cannot be certain W’ = 0J in the modeling should necessarily be an anchoring point for physical exhaustion. But if you can do a VO2max test and verify that you have reached VO2max at that point, then you can be sure W’ is empty. And that would also coincide nicely with exhaustion.
One has to be careful about the differences in what mathematical modeling says and what reality is.
I’ve using Dr Skiba and tried to match the settings with the ones in intervals.icu but they differ quite a lot. I can put the Dr.Skiba negative with several short burst with rest in-between and just today i went negative in the intervals (with a 3min effort) but far from it in the dr.skiba.
and you will better understand why the W’ model has a lot of shortcomings.
It’s best to use a CIQ field that let’s you change between the 2 different calculation methods. Just try ou both and see which one is better adapted tou your specific profile.
To be honest, I don’t know which one @david is using in intervals.
I’ve never worried about FTP exactly number once I gauge it based on power intervals durations but I was reading this thread and out of curiosity I went to double check my numbers an em got a doubt.
eFTP at power page shows 205W for this season and at fitness page 252W.
What am I missing here?
I’m very comfortable with 239w manually set.
Hey @david, may I say congratulations and thank you for showing the code? Most developers would never do that. This makes you a very rare and possibly unique developer. Well done!
This is very likely (I am not an expert either) the following:
eFTP from best effort this season is 205 W
eFTP from best effort last season was 267 W; if you don’t show comparably hard efforts, this slowly declines with time – for you down to 252 W
If you are happy with the ~240 W for training, that should just be fine, but seeing these numbers I’d assume you could sustain somewhat harder intervals;-)
What‘s there to know?
Assuming you understand FTP (which is in honesty really the hardest part, not only here), these eFTPs are approximations to your FTP, one based on the performance you showed last season, the other one based on performance you showed this season.
The actual approximation, e.g., using Morton‘s 3-point formula, are somewhat explained in the power page and the link to the original literature is provided there, too.
I was trying to do the same thing but found out it’s really hard to make it useful. Problems i have:
-you need to really have your FTP set on point (FTP changes from day to day)
-even if you compute your W’ the real problem is to compute the recovery rate (different for everyone)
-W is calculated from your max effort so using it during intervals can prevent you from reaching really deep
-i think it can be useful during hard rides just as a capacity value to look at when trying to go hard and all out, wahoo doesnt support it so i gave up, but at the same time during such hard effort looking at the Garmin screen seems hard to imagine and at the end if you consider one time all out effort what is the point of knowing when you reach reach your limit, you will reach it anyways
negative W means its higher than calculated or your FTP that day is higher than you think, or your rest rate is faster than the app thinks. Should you stop your interval seeing empty W? Maybe. Should you rise your computed W now? Maybe, but what if the next day you gave up on the last interval?
-i think it can be useful as a statistic variable, so after a month of Vo2 intervals you look at it and see if it changes or not like on your graph, but you don’t plan your intervals around your W just know that the planned earlier intervals are working.
But just as you, im interested in W so hope someone will find a nice way to make it more useful.
Forget about last season.
I would like to know about the difference between the eFTP showed for this season (207w) and and the eFTP showed at Fitness chart (252W).
It’s very clear in my first email.
Almost there…
The season eFTP is based on efforts performed during this season without historical impact.
The current eFTP is the historical value, declined or not and spanning over the different seasons.
@Lukasz_Pludowski You have it right about W’. It is no more then a guestimate. I can help to give you a starting intensity for anaerobic intervals but you will have to correct when it feels to easy or to hard. In my opinion, VO2max intervals should be done to failure, or almost failure. Always set up a workout with one extra interval and start that last one anyway. This can give you an idea of how much is left when the regular intervals are done.
The eFTP on the /power page is the best value you achieved for the curve selected (42d or this season etc.). The one on /fitness and shown on activities goes up with you do a good enough max effort and gradually decays if you reduce training load.