Work on the following, and you won’t go too far wrong. Better to over estimate, and end up with carbs in your back pocket, than bonk out on the ride from under estimating:
1Wh (into the pedals) = 1 gram of carbs required; this is a fair estimate.
This takes into account the conversion from Calories (food) to kJ, as well as the inefficiency of humans (20-25%). Long story, but I can explain in more detail, if needed.
If you ride at 200W for 3 hours, you will need 600g of carbs. Assume you start fully topped up, you have about 100g in your liver (glycogen stores), and about 300-400g in your muscles. Again, an assumption based on averages. 600g minus 400-500g, means you need 100-200g to get to the 600g total for 3 hours, but that will leave you close to depletion if you start with 400-500g in reserve.
That means 33-66g per hour at 200W average; Up to a 750ml bottle & gel (or real food) every hour.
Riding at low intensity will burn some fat, so the 200g/hour (at 200W average) does not mean you burn 100% carbs only. The higher the intensity, the more carbs you need to fuel the work being done.
This tried and tested formula is more for race-pace efforts, and not your low intensity rides.
I think your FTP is much higher than 175. You shouldn’t be able to ride at 122% of FTP for 20m. W’bal declines based on how much above threshold (FTP in this case, more correctly CP) you are. Every second at 214w drops it by 39w (20m = 1200s = 46.8 kJ drop).
The ride eFTP is 204w and on the /power page Intervals.icu has your eFTP at 204w and W’ at 12.9 kJ based on the last 42 days data. So you should more realistic W’bal chart with those numbers.
I’m referencing it to this I found in one of the links below and I’m not exactly sure what is TAU w/ a 546 as one of the default values., but it looks like the equation is the Differential.
But - so… based on what I read, which to use is largely based on “test and see”?
I’ll play around w/ both of these and perhaps have it as an option for users to choose. Of course, using the differential would be directly in-line w/ what intervals.icu uses so that’s the good thing.
// Method by differential equation Froncioni / Clarke
if (FORMULA == 1) {
if (pwr < CP) {
wprimebal = wprimebal + (CP-pwr)*(WPRIME-wprimebal)/WPRIME.toFloat();
}
else {
wprimebal = wprimebal + (CP-pwr);
}
}
// Method by integral formula Skiba et al
else {
// powerValue
if (pwr > CP) {
powerValue = (pwr - CP);
}
else {
powerValue = 0;
}
// Compute TAU
if (pwr < CP) {
totalBelowCP += pwr;
countBelowCP++;
}
if (countBelowCP > 0) {
TAUlive = 546.00 * Math.pow(Math.E, -0.01*(CP - (totalBelowCP/countBelowCP))) + 316;
}
else {
TAUlive = 546 * Math.pow(Math.E, -0.01*(CP)) + 316;
}
// Start compute W'Bal
I += Math.pow(Math.E, (elapsedSec.toFloat()/TAUlive.toFloat())) * powerValue;
output = Math.pow(Math.E, (-elapsedSec.toFloat()/TAUlive.toFloat())) * I;
wprimebal = WPRIME - output;
}
Somehow I’ve set my W’Bal at 17kJ. Now that I re-check , its closer to 9kJ and I’m not sure why. It’s likely due to me not doing any max effort of those 1m 3m 5m i’m guessing?
Really getting confused with all these numbers.lolz
Has your FTP increased?
Or rather, has your critical power increased?
If you are training your threshold power, and you end up with a higher FTP, chances are you CP is higher. Even if your max efforts 1s, 5s, 1m, etc. remain the same, the W’ will decrease.
It doesn’t mean you are less fit, it just means the balance between aerobic and anaerobic energy systems has shifted more towards the aerobic side. Think of it like a see-saw.
This is the best video I know that explains W prime (W’), but doesn’t explain how it changes.
More likely than not, it’s dropped. I rarely ever do FTP tests anymore. Hurts too much, but I just hammer on some outdoor rides and then use whatever Garmin Thinks I am at.
So basically, my W’Prime (on intervals) based on the 90d, Morton 3P data is saying that since I din’t do any FTP tests or have data at say 20m efforts, then my CP/FTP calc within Intervals would slowly decay and thus my corresponding W’Prime will also drop.
Is your Garmin IQ compatible?
If so, use the free Xert “What’s my FTP” IQ field. It is way better at judging FTP from random all-out efforts then Garmin’s Firstbeat guestimate.
Need to add to my original post, relating to the carbs per hour.
Getting 70-120g of carbs, assuming that’s your goal cannot be done by glucose alone due to the limit that your system can process per hour. One requires a combination of glucose and fructose, as they are transported to different parts of the system for use and processing.
Globose goes straight to the blood, while fructose goes to the liver first. A local podcast referred to the door and window as the entry point of glucose and fructose. The door is a certain size and can only allow a certain amount (glucose) through, while the window is smaller but can let a certain amount (fructose) through.
So when looking for an carb powder for your bottles, check that it has both (2:1 or 1:1 ratio) for your high intensity events.
It changes due to the fact that in the mathematical modeling, both W’ and CP are parameters in the same model. If the model delivers a higher CP, W’ parameter will decrease. And vice versa.
Is there any protocol or guidance on how to adjust W’ when one significantly dips into negative territory on some hard efforts ?
Today I did a 6 min test climb and depleted my full 22kJ all the way to -9kJ. This tells me I either need to increase CP/FTP or W’.
I’m always reluctant to increase CP/FTP as sustained efforts are my weakness and I don’t see the point in raising CP/FTP when my TTE is only at 45min. I fear setting incorrect training zones.
My current W’ seemed to work just fine for this winter training, regularly getting low during HIIT, but never getting negative.
This was an outdoor session, so maybe my power meter reads higher power being on the crank vs on my Kickr trainer or maybe I just can do harder efforts outdoors (it was fresh temperature vs sweaty indoors).
I’ll start by doing an outdoor FTP test. I’m generally using Wahoo System, but thanks to other threads on this forum I was able to replicate the 4DP test protocol and push it to my Wahoo head unit.
I’ll then recompare my W’ depletion for this activity using new FTP results and see where it lands. Is there any documentation on normal distribution of W’ balances? Is W’ balance supposed to be relatively constant? Any other suggestions to fine-tune my settings ?
I’m using Morton 3 Parameter.
Last I checked (couple weeks ago - coming back from injury) it was at 9xxx J
Today, I just checked and it shows an (small) increase.
Q: How would I know when I should check if the W’ has been updated? Or I should basically check each time after a hard ride (or rides where I “fed” the model)
Also, what does the hollow circles represent?
Note: XERT’s What’s My FTP did indicate I got a new FTP as well. So, check it when
Xert shows an increase in FTP
intervals.icu sends out the “nice ride - your ftp has xxx” email
Basically, if you check the activity page after the ride and see a negative W’ value, you now that you have to re-evaluate FTP and/or W’.
After an FTP change I always lower W’ and on the next rides, re-adjust.
Those are the points from your PDC that were used to match the model curve. They show only when you have set the option to show the model curve.
When you change FTP, W’ changes but you don’t know how much. I have the habit of lowering W’ after an FTP increase and when I see negative values on the next ride(s), I raise it again. If you prefer to start with the value returned on the PDC, that’s just as good but you might miss changes because you never go negative and don’t pay attention to it.
The value of W’ will never be totaly accurate. That’s just how it is…
If you do one single hard interval untill failure, you will have a different W’ compared to doing multiple shorter intervals were you fail on the last one. The reason is that W’ works with a default recovery constant that is an average returned by a number of studies. But every athlete is different and has a different Tau (recovery constant).
After a couple of rides where you went to failure, you will have a “decent” evaluation of your W’ but it’s absolutely useless to fiddle with the number every time you see a negative value. It’s only accurate enough to give you an idea of your anaerobic capacity.
On top of that, there are 2 different calculations around for W’. A differential and a integral one where recovery is significantly different.
So expect to see differences of up to 20% simply because of the differnet nature of one ride compared to another.
On the other hand, if your FTP remains the same and you are in Peak training phase, W’ almost surely will go up, just because your training targets the anaerobic capacity…
Anyway, it’s not a very important metric to follow-up on unless you do regular racing that has lots of demands on anaerobic capacity.
