I’ve been thinking about IM nutrition/calories recently. Do some people run poorly simply because they can’t burn fat well?
Lets post some numbers:
How many calories do we burn in an IM? I think I burned about 7200 in mine. 150pounds.
How may calories can we consume and then process? Is this trainable? Whats a reasonable range? The often quoted 280 cal/hour?
Given glycogen stores and consumption - how much fat do we need to burn? I’m thinking we gotta average at least 30% fat (For me - I think I burned about 7200 cals - 2000 stored glycogen - 3000 consumed = 2200 from fat = 30%?)
How many people run poorly not because they pace the bike poorly (#1 cited reason) or lack electrolytes (#2 cited reason) or just don’t run enough (Paulo’s reason) - but because they just aren’t good enough at burning fat?
Is an IF of about 72% where we burn enough fat to run well?
Are the best IM runners the best because they burn fat well? Is The Sergio a fat burning machine? Was Mark Allen?
Burning fat is a function of how far below your LT you can race. So, the really fit guys can pace properly and still go fast. Those who are not so fit need to be really careful…many aren’t and they blow.
However – most people walking aren’t walking because they ran out of fuel. They’re walking because muscular fatigue has overwhelmed their fitness level. Believe me, I had plenty of fuel during my 5+ hour stroll at Lake Placid. But I could not run a single step after 10 miles.
As Ashburn says, if you can run far from your LT you will burn fat. This means that you have to run lots to be able to run at a decent pace without bonking.
To prevent muscle fatigue you have to run lots…
We can talk about 1000 details that stopped us from performing but it all comes down to one thing… enough training!
I think running well is the key to a good performance (this means that running has to be the nr 1 prio in training).
Based on the way I read this post by Andrew Coggan, we really aren’t using fat as our primary energy source, even at a low IF or %of FPT while racing an IM
"3. Muscle practically always uses a mix of substrates, and only during very long duration, relatively low intensity exercise in the fasted state are lipids likely to be the predominant fuel. " from Coggan’s post here… http://forum.slowtwitch.com/gforum.cgi?post=1040489#1040489
Perhaps he can elaborate on this in terms of what he defines as “very long duration” as well as “low intensity”…
Well my understanding is that some people may burn 40% fat at “IM effort” and some people may burn 10% or less at the same relative intensity. It seems like its a lot genetic/muscle type - some of course is trainable - and some will be based on diet.
I have a friend who is pretty quick - but can’t burn fat well - he races great at sprints/oly’s - struggles on the run in half IM and can’t even finish a bike well in an IM. He has a power meter - I know his HR zones and power zones - he paces fine - more conservative than me - but he can’t race long - why? Because he can’t burn fat! He did a VO2 max test and in zone 2 still only burns about 10% fat - zone 3 its less than 5%…now how he could he possibly expect to be able to race for 4:30+ for a half of 10+ for a full?
How many other people are out there like that?
How trainable is “fat burning”?
I just think that there may be quite a few out there who don’t burn fat well and can’t race long…and it seems like its not talked about much at all.
Dave, I took in 3800 cals in my last Ironman and I weight 140 lbs. I lost 1.2 lbs over the race, likely the fluid that was stored on my body from carb loading. So likely 2000 stored, 3800 or so consumed (you can’t get to all of that) and then the rest from fat and eating into muscle protein.
Based on the way I read this post by Andrew Coggan, we really aren’t using fat as our primary energy source, even at a low IF or %of FPT while racing an IM
"3. Muscle practically always uses a mix of substrates, and only during very long duration, relatively low intensity exercise in the fasted state are lipids likely to be the predominant fuel. " from Coggan’s post here… http://forum.slowtwitch.com/gforum.cgi?post=1040489#1040489
Perhaps he can elaborate on this in terms of what he defines as “very long duration” as well as “low intensity”…
Multiple hours at <50% of VO2max (i.e., below the intensity at which even an Ironman is raced).
(Note that I should have also specified “…when consuming a normal mixed diet and with adequate initial glycogen stores.”)
I have a friend who is pretty quick - but can’t burn fat well - …
I’m just poking in here…how in the world would anybody know whether or not they can burn fat well? Falling apart in long events doesn’t mean somebody can’t burn fat well (despite what Mark Allen says). Some people just “fall off the curve” at a shorter spot that others due to a host of reasons. There are guys in my (former) tri club who simply slay me at short course, qualifying for worlds and whatnot. I can hang with them in half IMs, though. It’s not about fat burning.
Muscular fatigue is probably the biggest reason. Legs just get too tired and we can’t go on. The cure is straightforward – training volume – and the dose is different for different people.
The only way to know about substrate usage is via lab testing: doing workouts whilst breathing through a big tube.
The percent fat vs. carb burn was done in a lab breathing through a mask. It was a O2 Metabolic Assessment test. It was very interesting (as far as lab tests go) and changing some of the ways one train we’ll have to see if it the ratios of burn can be adapted.
Any exercise physiologists out there? How possible is it?
As already pointed out only at very low intensities for long period of times do we burn mostly fat. Also as pointed out we almost alway burn a mixture.
Now if someone races well at a short distance and can’t match the same “relative” performance at a longer distance I’ve always thought that to be a conditioning issue. Granted this may be in part due to “fat burning” but isn’t this part of training?
If someone trains an “appropriate” amount of distance and time for an IM but they do most of that training at to high of intensity, woudln’t they be training the wrong systems?
In l;aymans terms…casue that what I am, and highly exagurated, If I guy went out and did several 100 mile bike rides, but did all of the miles in 5 min repeats at a very hard effort, getting off and recovering when he/she could no longer go, then wouldn’t this be reason for poor “fat burning”
I think this is especially true in running where many people end up doing their LSD runs too hard. End up sore and wiped out for a couple fo days but think they have done a proper LSD run.
The percent fat vs. carb burn was done in a lab breathing through a mask. It was a O2 Metabolic Assessment test. It was very interesting (as far as lab tests go)
Interesting, perhaps, but I don’t really see much relevance to training prescription.
and changing some of the ways one train we’ll have to see if it the ratios of burn can be adapted.
Although the measurements are highly reproducible, I certainly wouldn’t rely on such information to modify someone’s training program.
Any exercise physiologists out there?
Several, but you don’t have to have formally studied the topic to know the answers to your questions (e.g., see Ashburn’s post)
How possible is it?
It’s been known since at least the 1920’s that endurance training alters the mix of substrates oxidized during exercise.
I agree that most lab tests are just that interesting. I get a lot more from doing a 3mile run or a power profile as a benchmark.
I was thinking however that the results of a low percent of fat burn could be a reason to alter a training plan or maybe more so to make sure that the correct zones are followed during the training.
"It’s been known since at least the 1920’s that endurance training alters the mix of substrates oxidized during exercise. "
Andy,
I would love to hear your “take” on what would constitutes effective intensities and durations of training to improve the ratio of fat to CHO one utilizes during IronMan length events. Many years ago, Dr. David Pendergast, implied to my wife that tempo/threshold paced training sessions of ~ an hour were optimal stimulus for improvement of many endurance enhancing systems including fat/CHO burn ratios. He was not a fan of LSD training to improve this ratio. We have not spoken in at least 15 years so his feelings about this may have changed with more research.
Thanks for all you bring to these discussions, especially keeping Paulo in line;)
What do you know! Someone actually brings up the idea that some, or a lot, of our success or lack thereof in triathlon or any endurance sport might be based upon genetics and God given talent. Novel concept that not many want to discuss much. It seems everyone wants to believe that with enough training we can do a 8:30 IM or a 2:30 marathon, but some of us never will, based upon genetics.
That’s why when I read inspirational quotes like “anything is possible”, I kind of chuckle. Do you think I can run a 2:10 marathon? No. I know those quotes are suppose to inspire us, but in reality they can set you up with unrealistic goals. Does that sound negative? Maybe, but it’s not, it’s just trying to be realistic, and when goals are realistic, then they can be achieved…
I do believe in the tables that Daniels and others have put forth that predict race times based upon VO2 max, LT, etc… Others may think they are bogus, but if someone is 40 yrs old, and they train and train and train for a marathon and the run 3:00 and the tables confirm that that’s about the best they will ever do, then how can he/she expect to run a 3:00 IM run split!? I don’t think it’s possible…
What does this have to do with this thread? Well, some people might only be able to run a 3:45 IM run based on genetics, that’s hard to accept. Maybe they can run faster. I’m NOT saying we should not try to maximize our talent and train for lifestyle and fitness benefits, but to think we all can accomplish super fast times without considering our natural talent is foolish…
Go ahead and rip this post apart! I don’t mind explaining further by using myself as an example- 42 year old…
It’s been known since at least the 1920’s that endurance training alters the mix of substrates oxidized during exercise.
I think the more interesting question is to first assume that a person is already well-trained. Then, they learn that they burn less fat at a given relative intensity than another similarly fit person.
(1) Is there anything they can do that will change this?
(2) Would it matter in an event like an IM? ie, should they bother?
Just guessing ahead a little…I would think that it might matter, to some racers; say, those with fantastic fitness and preparations who go long and fast enough to hit a fueling wall. Still – the vast majority of the people walking in an IM (or running far below their capabilities) are experiencing simple muscular fatigue rather than fuel depletion.
I already hear a response of sample size of n=1. Beyond that, I believe that there is no ONE way to train. Given the genetics we have a potential that we can reach in different ways or at least they sound different. The human body is pretty complex so we haven’t got a handle of the complex set of variables. At the same time, there is a powerful mind/body connection that is becoming more recognized here in the west.
the run 3:00 and the tables confirm that that’s about the best they will ever do
The Daniels tables don’t do that or claim that. They are not based on VO2max, but rather on actual, functional fitness. So, one would not know just how high one can climb up the Daniels tables. They would have to do other things to assess their potential limits.
However – I very much agree with you about genetics. I just doesn’t fit into the pollyanna views of our culture. I’ve tired of mentioning it because I find getting shouted down gets old after a while.
To think that what makes endurance athletes different from each other is purely training is akin to thinking that what makes Shaq a great NBA center is his training – that it has nothing to do with being born a 7+ footer. Or, maybe people think that Shaq is 7 feet tall because he tried harder. There is as much difference on the inside between me and Dave Scott as there is on the outside between me and Shaq.
The slippery slope of bring up this truth is that people can be prone to assuming that their limits are lower than they really are. I know I did.
Thanks for all you bring to these discussions, especially keeping Paulo in line;)
That’s really funny, especially considering that I don’t remember one instance when AC contradicted what I said. Maybe you’re mixing me up with somebody else?
I don’t mind explaining further by using myself as an example- 42 year old…