Fat/Carb usage - actual data, any more?
bahzob
Posts: 2,195
I had some lab tests done recently that involved doing a ramp test to exhaustion while being hooked up to a respirometer.
Amongst other things this showed the actual amount of fat and carbs being used up at varying intensities.
The results at lower levels (150W up to lactate [email protected]) are below and came as a bit of a surprise.
- There is an abrupt transition from burning mainly fat at 150W to carbs at 175W which I expected though at a higher level
- The total calories burned per hour is actually less at 175 and 200W than 150W which is a real surprise
- At lactate threshold there is a step change in energy usage (not a surprise), but this is mainly due to more fat being used (which is a surprise)
- Actual calories burned 175W+ is consistently less than those that would be guessed from the simple rule 1kJ = 1kCal. This is actually less of a surprise, when keeping a food diary I find I don't' shed weight as quickly as I would expect based on kJ of rides, this may help explain why.
This is a sample of 1 and ofc subject to all that implies. I plan a retest next spring to see what effect, if any, winter training has had.
If anyone has done same test and/or knows of similar data I'd be interested in seeing it for comparison. Also be interested if anyone has seen changes in these that they can ascribe to specific training methods.
Watts.......... HR ..........Fatg..........CHObg..... FatCal..... CHOCal....TotalCal............ kJ
150................................45............ 46............ 417...........188.......... 605............ 540
175................................15............113 ...........139 ........... 462 ........ 601.............630
200............................... 17............100............158............409..........566.............720
225...............133........... 25............115............232............470..........702.............810
(above shows watts, HR then g of Fat/CHO per hour for these along with calorie equivalents and kJ/h for wattage)
Amongst other things this showed the actual amount of fat and carbs being used up at varying intensities.
The results at lower levels (150W up to lactate [email protected]) are below and came as a bit of a surprise.
- There is an abrupt transition from burning mainly fat at 150W to carbs at 175W which I expected though at a higher level
- The total calories burned per hour is actually less at 175 and 200W than 150W which is a real surprise
- At lactate threshold there is a step change in energy usage (not a surprise), but this is mainly due to more fat being used (which is a surprise)
- Actual calories burned 175W+ is consistently less than those that would be guessed from the simple rule 1kJ = 1kCal. This is actually less of a surprise, when keeping a food diary I find I don't' shed weight as quickly as I would expect based on kJ of rides, this may help explain why.
This is a sample of 1 and ofc subject to all that implies. I plan a retest next spring to see what effect, if any, winter training has had.
If anyone has done same test and/or knows of similar data I'd be interested in seeing it for comparison. Also be interested if anyone has seen changes in these that they can ascribe to specific training methods.
Watts.......... HR ..........Fatg..........CHObg..... FatCal..... CHOCal....TotalCal............ kJ
150................................45............ 46............ 417...........188.......... 605............ 540
175................................15............113 ...........139 ........... 462 ........ 601.............630
200............................... 17............100............158............409..........566.............720
225...............133........... 25............115............232............470..........702.............810
(above shows watts, HR then g of Fat/CHO per hour for these along with calorie equivalents and kJ/h for wattage)
Martin S. Newbury RC
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PTP Runner Up 2015
Thanks,
Pete
It really does seem that the old idea of 'fat burning rides' is not as daft as some would have you believe. After all, if you deplete your carbohydrate stores by riding hard, then those stores have to be replenished if you are not to become fatigued and even chronically over-trained. Even if the body can replenish those stores by metabolising its own fat and protein, it seems quite possible that, if one is also running a calorie deficit in order to lose weight, one might still suffer from reduced energy levels, or even lose muscle mass.
One small thing. Please don't take this personally, but do you think that the figures are accurate? I ask because a power output at threshold of 225 watts does seem rather low for a trained athlete. I am an old giffer and my threshold at the moment is around 290 watts, and when I was younger and a reasonably competitive second cat it was around 330 watts. To put things into perspective, are you perhaps a slightly built female? (Or looking at that low heart rate at threshold, a veteran) .
I wonder how generalisable the figures are? For you the transition from being predominantly fat burning to burning carbs comes at 67% of your threshold. I wonder how large the natural variation in this figure might be. I also wonder, like yourself, exactly how much this 'threshold' point can be modified as a result of training.
A top class 60kg rider would need to be putting out 300+ watts, a 90kg rider would want to be putting out 450w+
I know that, which is why asked! Knowing bahzob's weight and so forth would add a bit of context. For example, having a heart rate at threshold of just 133 does seem very low, mine is 173 -175 and I am in my 50's!
I also note that bahzob has said that they have come in the top 200 in the Marmotte, which I recon would need an 'all day' power output when climbing of over 3.5 w/ kg, equating to a threshold of perhaps 4.5 /kg, which would put bahzob's weight at a shade under 49 kg, or 7 stone 10!
For what it's worth I am a little under 75 kg at the moment, when I am fully hydrated and my glycogen stores are fully replenished. When I was putting out 330 watts or so I was under 74 kg. Thing is, with the passage of time I recon that I would need to get down to 71 -72 kg to have the same % body fat as I did then, so that is my goal for next year, along with finding a few more 'lost' watts!
Well, according to those numbers, your gross efficiency varies wildly with intensity:
Watts GE
150 21.3%
175 25.1%
200 30.4%
225 27.6%
Let me know the lab. I'd like to avoid it.
That's my cheeky way of emphasising that relative fuel substrate utilisation is a function of many things, only one of which is exercise intensity.
I'm 54,5'8" and my weight at the moment is 67.5kg. (when I did the Marmotte it was 70kg, finished top 350 in that, top 200 was the Etape)
Re threshold I think you made the same mistake I used to make and loads of others still do.
Lactate threshold is defined here http://en.wikipedia.org/wiki/Lactate_threshold
The key word here is "starts" in the definition "lactic acid) starts to accumulate in the blood stream"
By definition this will occur relatively low in a ramped test. While a blood test is needed to establish it accurately it occurs around the time when you have to start breathing steadily through the mouth to keep things comfortable. In zone terms its endurance pace, I'll be aiming to sustain 225W for 12 hours next year.
There is a second point that occurs later on during a ramp test. This is the maximum amount of lactic acid concentration you can maintain over timeso is sometimes referred to Maximal Lactate Steady State or MLSS. It's also pretty much around what your FTP is and it's this one that is sometimes also called, mistakenly by me included, "Lactate Threshold". FWIW mine was 300W this test along with a VO2 of 62.8 which are both a bit low as I have been mainly focussing on weight loss recently and done very little top end workouts. (Indicated by the fact that in this test my HR hit 180rpm, it's rarely been in the 170s last month or two)
I see your point about the use of the term 'threshold', but the same word is used to refer to a number of different things, and to when I use the term I am usually thinking about 'time trial' levels of intensity.
By the way, it is interesting just how close your FTP is to my 'guesstimate' for a rider who could do the Marmotte (or rather a L'Etape...) as fast as you have, at 4.44 w/kg for 67.5 kg and 300 watts
Cheers!
I've been wrong in the past and used "lactate threshold" to mean my FTP. I realise now this is a mistake and also how useful a figure "lactate threshold" is, in the events I take part in it's at least as important as FTP but doesn't seem to get anywhere near as much coverage.
I guess this may be because it requires a lab test to measure exactly, but from my experience you get pretty close just from watching your breathing, CO2 kicks up at around this point and this is what triggers the urge to have to start breathing through the mouth to expel it. My plan over the winter is to try and increase it then retest in spring to see how this has gone.
Re your guesstimate, yes it is interesting. From my experience there are 2 main predictors of how well someone will do in an event like this.
- w/kg
- pacing: specifically the ability to maintain high steady power on all the climbs.
As examples you might want to take a look at these analyses of me vs various better riders. My power dropped far more on each climb than the others did
7 hour rider
http://mr-miff-on-tour.blogspot.co.uk/2008/07/marmotte-and-power-revisited.html
Top 10 rider
http://mr-miff-on-tour.blogspot.co.uk/2008/07/marmotte-compared-to-best_17.html
Etape top 200 vs pro figures from TDF stage
http://mr-miff-on-tour.blogspot.co.uk/2009/08/ventoux-2009-pro-comparison.html
4.9 w/kg and you would have missed the time cut by 20minutes on this years etape.
Giant TCR 2012
What happened on the Glandon descent? The faster guy really put some time into you
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??? translation please. What's the point of this comment?
Sorry, you mentioned the comparison about top 200 vs the pro's.
I was trying to say, you need more than 4.9w/kg (FTP) to get within the time cut of this years Annecy stage
Giant TCR 2012
Well that is one area you could improve on and pick up 'free' time towards your goals. Cornering is cornering, no matter the size of hill you're going down
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Or become a better descender!
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Interesting. What time cut are you referring to? It's not the broom wagon I guess or there wouldn't have been many finishers.
Or do you mean that's what needed to get into top 200? Like to see the data if you have it so I can update blog.
Not sure I agree. Tackling one corner is one thing. Maintaining speed through a succession of curves for the best part of 20 minutes plus is another matter, especially if done in the company of a host of other riders of widely varying ability.
And I am not sure I know of anywhere in the UK that has 180degree 10%+ hairpins like you see in France.
Whatever I know it's a fault and am working on it. As it happens in the Marmotte the Glandon descent is neutralised now so at least that's one thing I don't need to worry about if I do the event again.
Ah, kk that makes sense I guess though didn't think anyone said they wouldn't.
That said I know for sure this isn't the case for the etape I rode in since it was won by http://en.wikipedia.org/wiki/Dimitri_Champion. Comparing finish times in amateur races to pro ones is difficult because of all the benefits the latter derive.
Just for laughs though, in fact I'd be willing to make a small wager that the top few finishers in an etape could get within the time limit of the actual stage especially now, the pro races at least, are pretty clean.
I don't have any stats for this years etape stage for that stage but there are some for the harder "double alp" stage here.
http://home.trainingpeaks.com/races/2013-tour-de-france/stage/18.aspx
This is from a Sky rider, the two climbs of the Alpe averaged something like 4.7w/kg and he was pushing it on the first ascent. I'm guessing that those in the autobus would be taking things easier with w/kg correspondingly lower.
The benefit being natural talent and hard work?
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