Glycogen Repletion Advice

[romistrub]

Who knew?

So I was running some quick calculations regarding carbohydrate requirements for strength training, and was getting some numbers that conflicted directly with those presented in The Ketogenic Diet (Lyle McDonald).

Note: Glycogen is usually measured/stated as a concentration of mmol glucose (monomer) per kg of wet muscle.

For weight training, the amount of carbs needed will depend solely on the amount of
training being done. [...] Individuals on [a standard ketogenic diet] typically maintain glycogen levels around 70 mmol/kg and performance will be extremely compromised if glycogen is lowered to 40 mmol/kg[...]. [...] we can estimate how much carbohydrate is needed to replace that amount of glycogen. To convert mmol of glycogen to grams of carbohydrate, we simply divide mmol by 5.56.

I abbreviated the text to exclude references to sets and reps, since they are irrelevant for this discussion, except to note that about 1.3 mmol/kg of muscle glycogen is depleted for one 70%1RM rep.

The bolded part confused me. I have read many studies regarding rates of glycogen resynthesis, and this statement was not referenced. It took me a while, but I figured out how the number was arrived to:

1) The molar mass of glucose is 180.6 g/mol.
2) 1 mmol/kg / 0.1806 g/mmol = 5.54 g/kg

Unfortunately, there are multiple mistakes in making this calculation!

1) The molar mass of the glucose in polymer form is actually 162.6 g/mol (less at branching sites and more at terminal sites). Not particularly important, but not irrelevant. The correct factor would be closer to 6.15.

2) The subsequent recommended carb intake is *per kg of muscle mass used*, but this is not stated.

3) The recommendation assumes that 100% of ingested carbohydrate is used to replenish glycogen, which is not even close to true. Studies indicate that, at most, about 30-40 mmol/kg(dry weight)/hr can be replenished, regardless of carbohydrate intake (the rate maxes out at around 1.2 g/kg(LBM)/hr).

4) One rep at 70% 1RM uses about 5.85 mmol/kg(dry) of glycogen. A single fill-body set of 5 reps at 70% 1RM requires about 30 mmol/kg(dry), which takes about an hour to resynthesize at 1.2 g/kg(LBM)! Obviously a substantial amount of the ingested carbs are not going to resynthesize glycogen.

What's the take-home message? Lyle McD's recommendation:

for every 2 sets performed during weight training, 5 grams of carbs should be consumed

My recommendation is that you consume 0.2g/kg(LBM)/rep of carbs to replenish glycogen up to a maximum of 1.2g/kg(LBM)/hr. (Here, the rep represents a "full-body rep" at 70% 1RM. No such exercise exists but I have to make this approximation since peoples' muscle distribution varies).

For example, my typical workout involves 25 full-body reps at an average of 70% 1RM (guessing at that one -- it's probably a bit more), and my LBM is about 70 kg. Using these numbers, I would consume 350 g of carbs before my next workout to replenish glycogen.

 

[romistrub]

I should point out that the studies testing maximal glycogen repletion rate also tested repletion rate using submaximal glycogen intake with added protein. The CHO+Pro mix almost stimulated the same quantity of glycogen as did the isocaloric CHO mix (35 mmol/kg(dry)/hr vs 40 mmol/kg(dry)/hr). As such, I would actually recommend consuming a mix of CHO+Pro at a ratio of about 2:1. Extending my example above, that would result in about 230 g CHO required before the next workout. This is more accurate and realistic, since most carbohydrate will be consumed in the form of a mixed meal, and not a glucose (polymer) drink. For me, that means about 180 g in the first 24h, and 50 g in the next.

 

[junkyard dog]

Way to confusing for me to figure out, I like to keep things much simpler.

The info is very interesting though how it is broken down the way it is. Hard to say how accurate the stuff is though compared to other methods/peoples views

 

[Monger]

3) The recommendation assumes that 100% of ingested carbohydrate is used to replenish glycogen, which is not even close to true. Studies indicate that, at most, about 30-40 mmol/kg(dry weight)/hr can be replenished, regardless of carbohydrate intake (the rate maxes out at around 1.2 g/kg(LBM)/hr).

Ya, but I don't think those studies imply that carbs consumed in excess of 1.2g/kg/hr are not used for glycogen storage. In other words, just because the rate maxes at X per hour doesn't mean that if you consume X+2 it won't be utilized in the same way but obviously taking longer than an hour. Or maybe that wasn't your point, I don't know.

And I won't pretend that I've looked into all of these calculations as much as you have because I haven't. But, I don't really see the point in being so detailed and obsessed with the numbers here (though it's something I can admire).

1. What benefit do you get, personally, from having glycogen completely topped off at every WO?

2. Studies have also shown that with almost any reasonable carbohydrate diet, glycogen levels are always restored within 24hrs.

Call me crazy, Bro... but I just don't see the need to worry about this in such detail.

Besides, there

 

[Monger]

For example, my typical workout involves 25 full-body reps at an average of 70% 1RM (guessing at that one -- it's probably a bit more), and my LBM is about 70 kg. Using these numbers, I would consume 350 g of carbs before my next workout to replenish glycogen.

Are you saying that your calculations conclude that, on average, your weight training workouts are utilizing 350g of carbs via stored glycogen? Maybe I'm misinterpreting what you're saying, but if I'm not, that number is absurd.

That would indicate that you're burning an excess of 1,400 calories for a single hour in the weight room. And I say excess because a certain amount of fat will also be oxidized on top of this number not to mention glucose circulating in the blood stream. Most people are lucky to burn 300-400 calories an hour with typical weight training.

Honestly, Lyle's recommendation of ...

for every 2 sets performed during weight training, 5 grams of carbs should be consumed

...seems to be a lot more reasonable. That would put a 25 set workout at ~60g of carb utilization which would be ~240 calories and that seems pretty decent for a ballpark figure.

 

[junkyard dog]

I think it means that from postworkout up until the next workout one would consume 350g carbs to replenish glcogen.

Possibly 24 hrs in between to consume 350g carbs, im kinda confused to but thats how im understanding it.

350g carbs per day is a bit high depending on what kind of training and what ones goals might be. Who knows though

 

[modena1983]

1. What benefit do you get, personally, from having glycogen completely topped off at every WO?

I was wondering this as well.

 

[JSN]

i'm not 100% sure what you're asking, but if you crunch the numbers, his estimated amount of glycogen used per set = 5.4g glucose per kilogram muscle.

remember that you in his plan your ingesting glucose, not glycogen. that is why you wouldn't use the polymeric mass.

i think you may be looking at this mess of a poorly worded paragraph and thinking his methodology is different than it actually is. you're upside down on your conversion factor. .1806g glucose/mmol / kg bodyweight is the conversion factor, not the inverse. multiply that by the 30 mmol he says you use in a set and you have his recommended intake per set.

i think you may be looking at the sequence of the paragraph and thinking his estimates come about backward how they actually did.

just to clarify, the conversion factor is .1806 g/mmol glucose PER kilogram muscle mass.

 

[romistrub]

Ya, but I don't think those studies imply that carbs consumed in excess of 1.2g/kg/hr are not used for glycogen storage. In other words, just because the rate maxes at X per hour doesn't mean that if you consume X+2 it won't be utilized in the same way but obviously taking longer than an hour. Or maybe that wasn't your point, I don't know.

The thing about that study is that the subjects consumed CHO every hour at that rate. You're right, you could consume a lower-GI carb, but it's pretty well documented that the first of the two mechanisms of glycogen repletion, which lasts about four hours and is the most acute, is insulin-dependent. The second occurs over the 24-30 hours you spoke about and is insulin-independent. If you are "targeting" the second mechanism (low GI carbs, etc.) then your maximum intake would be far less than 1.2g per hour, although each feeding would contain far more carbs.

1. What benefit do you get, personally, from having glycogen completely topped off at every WO?

I don't actually top it off every workout. I try to maintain just enough to keep me going during each workout. If I have a really long session coming up (sometimes I'll be doing stuff for hours and hours with my friends on weekends) I might shoot for supercompensation, but that's mostly for giggles.

2. Studies have also shown that with almost any reasonable carbohydrate diet, glycogen levels are always restored within 24hrs.

I haven't seen these. It probably depends on what you believe is "reasonable" carbohydrate. My diet often contains less than 50 grams of carbs, sometimes less than 20, when my diet consists of veggies, meat, and a bit of fruit. I would agree that most average people consume an easy 150g of carbs per day, but that's not the case for a lot of people here.

Besides, there

 

[romistrub]

Are you saying that your calculations conclude that, on average, your weight training workouts are utilizing 350g of carbs via stored glycogen? Maybe I'm misinterpreting what you're saying, but if I'm not, that number is absurd.

You are misinterpreting, and you made the same mistake Lyle did: not even close to all of the ingested carbs go to replenishing glycogen.

 

[junkyard dog]

Quote:
Originally Posted by junkyard dog
Hard to say how accurate the stuff is though compared to other methods/peoples views

Xtrainer? Where are you? You need to be on top of this shit.


Quote:
In conclusion, nutrition is not a matter of opinion. To use the term I used earlier, "biology happens," and how feel about what we eat has no bearing on that fact.

Im kinda confused with this, Im sure there are other scientific methods similar to the original post and those are the methods/views i was thinking of.

I was just curious as to how close this study could or does resemble other similar studies.

 

[romistrub]

i'm not 100% sure what you're asking, but if you crunch the numbers, his estimated amount of glycogen used per set = 5.4g glucose per kilogram muscle.

The problem is that you can't just equate ingested glucose to glycogen via a simple conversion factor like that.[/QUOTE]

 

[JSN]

What assumption are you working from?

 

[Monger]

The thing about that study is that the subjects consumed CHO every hour at that rate. You're right, you could consume a lower-GI carb, but it's pretty well documented that the first of the two mechanisms of glycogen repletion, which lasts about four hours and is the most acute, is insulin-dependent. The second occurs over the 24-30 hours you spoke about and is insulin-independent. If you are "targeting" the second mechanism (low GI carbs, etc.) then your maximum intake would be far less than 1.2g per hour, although each feeding would contain far more carbs.

1. There is a time immediately PWO when glycogen synthesis is independent of insulin.

2. Digestion isn't immediate and that changes a lot. The more you eat, the longer digestion takes. When thinking in terms of hourly rates, that's relevant.

I haven't seen these. It probably depends on what you believe is "reasonable" carbohydrate. My diet often contains less than 50 grams of carbs, sometimes less than 20, when my diet consists of veggies, meat, and a bit of fruit. I would agree that most average people consume an easy 150g of carbs per day, but that's not the case for a lot of people here.

Yes, "reasonable" is definitely up for interpretation. It's been a long time (possibly years) since I've seen those studies so I don't recall the carb amounts used to determine "reasonable". But in the given context, reasonable will be pretty much close to average. Just making an assumption based on everything I've seen... reasonable, in this case, probably means 200-300g a day (assuming non-obese that are not over-eating).

Are you talking about enhancing fat metabolism? It really depends on the level of intensity of endurance exercise in question. In general, improving a metabolic pathway involves doing work with that pathway.

Mostly, I'm referring to AMPk activation and adaptations that go along with (mitochondrial biogenesis probably being a big one).

 

[Monger]

You are misinterpreting, and you made the same mistake Lyle did: not even close to all of the ingested carbs go to replenishing glycogen.

I may have misinterpreted, but I'm not sure I did in the way that you mean.

Bottom-line is this, if you have to consume 350g to refill glycogen stores from an exercise bout... how can you not correlate that to using 1,400 calories during training? Ok, knock off 6% for TEF or whatever but it's still an absurd number.

If I'm misinterpreting here, it would be that you are NOT saying that you require 350g of carbs to refill your glycogen after a single exercise bout. So I ask you, are you saying that? If not, WTF are you saying the 350g represents? You can tell me that only 40% goes to glycogen (which I'm not sure I buy that, I'd have to see specific references and context) but WTF are you doing to burn the other 60% without storing it as fat?

 

[JSN]

Lets not forget that a massive amount of that glycogen used is simply coverted to lactate that can be reconverted into glucose. Honestly this whole thing smells. It's not like
you you deplete you liver glycogen stores during exercise. Like monga has said, increasing research has generally shown that nutrient timing is crap; these guys wouldn't sell many books if they told people to eat a decent diet and that be the end of it.

 

[Vedic]

:icon_chee

I should point out that the studies testing maximal glycogen repletion rate also tested repletion rate using submaximal glycogen intake with added protein. The CHO+Pro mix almost stimulated the same quantity of glycogen as did the isocaloric CHO mix (35 mmol/kg(dry)/hr vs 40 mmol/kg(dry)/hr). As such, I would actually recommend consuming a mix of CHO+Pro at a ratio of about 2:1. Extending my example above, that would result in about 230 g CHO required before the next workout. This is more accurate and realistic, since most carbohydrate will be consumed in the form of a mixed meal, and not a glucose (polymer) drink. For me, that means about 180 g in the first 24h, and 50 g in the next.

*sigh*

 

[Vedic]

The thing about that study is that the subjects consumed CHO every hour at that rate. You're right, you could consume a lower-GI carb, but it's pretty well documented that the first of the two mechanisms of glycogen repletion, which lasts about four hours and is the most acute, is insulin-dependent. The second occurs over the 24-30 hours you spoke about and is insulin-independent. If you are "targeting" the second mechanism (low GI carbs, etc.) then your maximum intake would be far less than 1.2g per hour, although each feeding would contain far more carbs.

I don't actually top it off every workout. I try to maintain just enough to keep me going during each workout. If I have a really long session coming up (sometimes I'll be doing stuff for hours and hours with my friends on weekends) I might shoot for supercompensation, but that's mostly for giggles.



I haven't seen these. It probably depends on what you believe is "reasonable" carbohydrate. My diet often contains less than 50 grams of carbs, sometimes less than 20, when my diet consists of veggies, meat, and a bit of fruit. I would agree that most average people consume an easy 150g of carbs per day, but that's not the case for a lot of people here.



Are you talking about enhancing fat metabolism? It really depends on the level of intensity of endurance exercise in question. In general, improving a metabolic pathway involves doing work with that pathway.

You know what glut4 and other physiological responses to workouts do correct? You are splitting hairs over non-sense.

 

[romistrub]

1. There is a time immediately PWO when glycogen synthesis is independent of insulin.

2. Digestion isn't immediate and that changes a lot. The more you eat, the longer digestion takes. When thinking in terms of hourly rates, that's relevant.

agree

Yes, "reasonable" is definitely up for interpretation. It's been a long time (possibly years) since I've seen those studies so I don't recall the carb amounts used to determine "reasonable". But in the given context, reasonable will be pretty much close to average. Just making an assumption based on everything I've seen... reasonable, in this case, probably means 200-300g a day (assuming non-obese that are not over-eating).

disagree -- I regularly intake near 30g of carbs or even less on some days. I don't really eat any starches at all. I just don't like them.

Mostly, I'm referring to AMPk activation and adaptations that go along with (mitochondrial biogenesis probably being a big one).

ok

 

[romistrub]

I may have misinterpreted, but I'm not sure I did in the way that you mean.

Bottom-line is this, if you have to consume 350g to refill glycogen stores from an exercise bout... how can you not correlate that to using 1,400 calories during training? Ok, knock off 6% for TEF or whatever but it's still an absurd number.

If I'm misinterpreting here, it would be that you are NOT saying that you require 350g of carbs to refill your glycogen after a single exercise bout. So I ask you, are you saying that? If not, WTF are you saying the 350g represents? You can tell me that only 40% goes to glycogen (which I'm not sure I buy that, I'd have to see specific references and context) but WTF are you doing to burn the other 60% without storing it as fat?

I had an insanely long response to this typed out, and gave up. I'm in a bit over my head, lol. My logic is summarized as this: if carbs+protein (e.g. 40g/40g) increase the rate of glycogen synthesis beyond carbs (e.g. 40g, not 80g), and if this cannot be accounted for by the gluconeogensis from exogenous protein (40g), then it must be that the ingested protein somehow (insulin?) admits more carbs to be used for glycogen synthesis, implying that they are not all used in the first place. The numbers indicate that this is true [1], and an increase in glycogen storage of about 40% is observed over carbohydrate alone.

[1] Carbohydrate-protein complex increases the rate of muscle glycogen storage after exercise