Carb utilisation and ingestion on activities

Activities now show carbohydrate utilisation in grams and you can capture how much you ingested:

Columns are available on the activity list view:

Carbohydrate utilisation is calculated using the TSS model from this paper by Rothschild et al.:

Notes:

  • VO2 at VT2 is estimated from FTP
  • Activities with a variability index (normalised power / average power) of less than 1.10 are considered “continuous”
  • Prior day S-RPE is estimated from total training load on the previous day

So this only really works for cycling for now. I need to find out how to estimate VO2 at VT2 from heart rate data.

Re-analyse older activities to see this data.

This video explains the concepts and calculations well (tx @Jeff_Schiller1):

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Thank you.

At the end of a ride, my Garmin prompts for calories and hydration. Are you planning on fields for that, and auto-importing? I usually eat the same food and carbs in are a % of kcal recorded on the Garmin and in the fit file.

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Thank you David.

I’m tracking the kcal-value on my Garmin, like @WindWarrior mentions, after the ride.
Edit: this would be for the CHO in value.

My carbs/kcal are based on the actual foods I consume on the ride. fatsecret.co.za is the data source to get the (estimated) carb/kcal values, then completed on a spreadsheet before the ride, so I know what value to enter on the Garmin at the end of the ride.

4 hour ride

6 hour ride, 100 miles, on a super hot day

This is on the lower limit of energy needs, and not a specific amount.
Even if the net results shows green, it’s not the max tolerable.

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I think that it could be a good thing to manually enter the vo2max and LT2 manually (for those who has a metabolic cart data or lactate tests)

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Thanks for this. Is it possible for me to use this value to calculate intake per hour? If so what is the “CHO In” field called for the script?

Thanks in advance.

Hello @david ,

Thanks for the new “CHO Used” info you added.
I just added this info for my list of rides in the activities summary, and I’ve noticed on activity for which the “CHO Used” is: 4294967275.
Activity duration: 01:58, 418m ridden…

The ID is the following, hope this helps: i52959462

Thanks,
xavier

Nutrition Game has changed sport. There is not doubt about it. Let’s work together with our infinite abilities and knowledge and get this type of thing working efficiently.

Everyone knows that every platform produces an interesting carb and fat use number based on their equations. Let us improve this one so the tool we use is the best. It won’t happen over night or without the help of this community!

Thanks David for implementing so quickly.

Jeff

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Thanks. That activity should not have got “CHO used” at all. I have fixed that bug.

Yes that should be easy to do. The new fields are carbs_used (“CHO”) and carbs_ingested (“CHO In”).

Unfortunately it doesn’t look like Garmin sends that through. I edited one of my rides on GC and changed that value + filled in RPE and all the other stuff. Intervals.icu received an update promptly but it didn’t contain any of that stuff. The original activity notification also didn’t have it.

The video with worked examples was key! Tx.

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Thanks @david ,

Following your fix, the CHO for this activity has gone, but also for all my “Rides” (no power meter, only HRM). CHO is still available for “Virtual Rides” (power meter & HRM).

Is that the expected behavior?

Thanks,
X.

If you record hydration and nutrition on the Garmin at end of ride, it’s recorded in the original FIT file.

Editing in GC will not update and add the info to a FIT file. In my experience. Which matches yours.

I’ll post a FIT file message with the info.

Unfortunately yes. I still need to figure out how to make this work for activities without power.

Aha. I will have a look at some of my rides on fitfileviewer.com.

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It’s in the header details (top right of the activity).
image

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had to recalculate the activity, then it showed up. Thanks!
Interestingly, the video mentioned that it makes sense to adjust your daily intake to your daily requirements. What is the reason for this? What happens if the weekly total matches but not the daily one?

Which Garmin are you using?
The 530 records the data, but it doesn’t show in my .fit file

Edit: Looks like it’s field 177 (when in developer mode).

Two more things:

  • It kind of seems it makes a big difference if an activity is continuous or not. By the 1.1 variability test, almost all of my activities seem like ‘interval’ ones. I am not sure this is a good metric since sometimes I have a very easy ride just pimped by an interval at the end. Oviously I didn’t burn too much during that activity just because of those last minutes. Conversely, an activity performed only at threshold (say 30’ at Z4) would have a low variability but probably also a low fat burn percentage. I guess this ‘intervalness’ of activities needs to be revised.
    I just checked many of my activities to get a feeling for the algorithm and in most cases, the CHO out is roughly equal to calories burned/4, which would indicate no fat burn at all - and most of those activities are not really high intensity. In some cases, the CHO*4 even exceeds the total calories!
  • can you maybe implement a user setting for VT2 for anyone with a lab measurement?

I’ve just seen this on my last activity. It seems very high for what was an easy 60m endurance ride . 124g CHO for 428kJ ride at 57%intensity. Xert had it at 37g and Sentiero at 39g

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I got a running Lactate treshold test with VO2 and carb/fat burn a few months back. I came back with 192 gr/carbs/hr at LT1 and ~320 gr/hr at LT2.

I’m a 90-91 kg male, so there’s that. But 124 is not that crazy.

I have a 68min run, Low to mid Z2, givinig me 195 gr/hr. That seems quite on point.

124g/hr CHO for me at 124W NP (My LT1 is about 165W/175W) is very very high. If that was correct I’d be bonking on every long ride I did. A had a metabolic test done some years ago and I was burning 124gCHO at 21OW and with the amount of low intensity training I’ve being doing since then I would be very surprised if it wasn’t less now.

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I’ve just noticed this and, as others have noted, the CHO requirement for my latest activity (I haven’t checked any others) is way too high – CHO 1173g (= 4692 kcal) for a ride with an estimated calorie burn (based on power meter data) of 2502 kcal. Teething problems from carbohydrates – a dentist wouldn’t be surprised :grin:

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right. Here is a 2+ year old ride recorded on 530, synced to TrainingPeaks, and I downloaded the TP version and loading in FitFileViewer:

Field 177 is calories consumed
Field 179 is fluid consumed

This is Garmin Connect view showing the same 300 calories consumed, and 1302 ml fluid consumed:

In case is wondering why I consumed so little, I ate a big carb lunch about 2 hours before and a carb centric dinner immediately after the ride.

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