How much of an averse effect does glycogen depletion have on power output? Does the risks (if any) outweigh the benefits? meaning does being at a smaller mass with a depleted glycogen storage outweigh the benefits of a full storage associated with larger mass?
in what context? sprinting, lifting weights, endurance training?
many find that they are somewhat stronger (weight training) supercompensated. but you’ll typically be heavier too. which may or may no matter on the platform
for something like sprinting, where muscl glycogen is absolutley irrelevant to perforamnce, the weight gain (which can potentially reduce power:weight ratio) could be detrimental
for an endurance athlete, it would depend. a cyclist on the flats doing a very extended race might benefit. a cyclist climbing a hill might be hurt b/c of the added weight. a runner (who is carrying relatively more of their total weight) might have decrements, that has to be weighed against th elngth of their event
finally, comparing glycogen supercompensated to depleted is a bit silly. the guy who has normal glycogen might do better than either extreme (again, depending)
Lyle
http://www.bodyrecomposition.com
http://proteinbook.lylemcdonald.com
http://www.bodyrecomposition.com/blog
This is of topic but, would a ketogenic diet be advised during off season (no high intensity exercise that demands carbs) to reduce fat while sparing muscle mass?
it can certainly be used for such although going purely ketogenic is not usually necessary to accomplish this
muscle mass sparing is mainly an issue of adequate protein, ketosis is pretty irrelevant (except whn protein is inadequate in the first place)
however, when high intensity trainng demands are down, there’s no reason to keep pumping in massive amounts of either calories or carbs.
the idea of periodizing nutrition around the different aspects of training makes total sense. So when volume/intensity is down, carbs and calories can be brought down. coupled with a bit of extra tempo or whatever can get an athlete lean before he’s into high intensity work.
then raise calories/carbs when intnsity/volume goes up to support optimal adaptations
Lyle
http://www.bodyrecomposition.com
http://proteinbook.lylemcdonald.com
http://www.bodyrecomposition.com/blog
since ketosis is irrelevant during adequate protein intake, in a high proten, low carb, low fat diet does the body prefer fat or protein or a mixture for energy? Also dont body builders use a pure ketogenic diet to cut fat before competitions?
to a degree nutrient oixdation will shift with intake. but generally the deficit will be made up from fat. this is impacted greatly by a lot of actors such as starting bodyfat percentage
Also dont body builders use a pure ketogenic diet to cut fat before competitions?
we need to define a ketogenic diet here
technically, a ketogenic diet is any diet that is less than 100 grams of carbs
the rest of the definition will depend.
the ketogenic diet ala epilepsy is very high in fat
most popupar ketogenic diets such as ATkins/Protein power etc. are as well
but they needn’t be and, from the standpoint of maximum fat loss probably shouldn’t be. fat loss will ultimately come down to fat balance which is defined as
fat oxidation - fat intake
on a low-carb diet, fat oxidation goes way up. but if fat intake goes up as well, the net fat balance is affected
it still comes down to calorie balance/what the person can sustain
but at the end of a contest diet, when bodybuilders have to
a. cut claories hard
b. keep protein up
There simply isn’t much room for other nutrinets to typically carbs AND fat go way down. my rapid fat loss handbook is based around this idea. you consume sufficient protein to limit LBM losses, consume EFA’s for nutrient intake and you take literaly nothing else. This maximizes negative fat balance to maximize fat loss per unit time.
Lyle
http://www.bodyrecomposition.com
http://proteinbook.lylemcdonald.com
http://www.bodyrecomposition.com/blog
So basically on a low carb diet the fat burning process does not occur until 4-10lbs of glycogen is depleted. this is why those who loose weight and stop dieting during the first few weeks gain it back. just curious what is the ratio of fat to protein oxidation during low carb conditions?
Hi Lyle,
What are the implications for dramatic weight loss on sprinters? Do you feel it is a net hinderance or help on performance.
For instance if the body becomes more efficient as utilizing stored fat as a fuel, does this impact on the ability to produce energy through anaerobic glycolysis or is the effect limited to daily functions and repair?
Thanks
no. the body will be in pretty much a maximum fat burning mode by about day 3, whether glyocgen is depleted or not
this is why those who loose weight and stop dieting during the first few weeks gain it back. just curious what is the ratio of fat to protein oxidation during low carb conditions?
it depends on initial bodyfat
in fat indiviuals, fat oxidation can make up 93% of the total fuel mix oxidized
in lean individuals, it’s something like 70% (I forget the exact numbers)
which is why fat people don’t need as much dietary protein to spare muscle loss on lowcarbs compared to leaner people.
I think it will depend on how it’s done but I wantto make it very clear up front that I haven’t worked with sprinters.
But I have some experience with powerlifters tryign to make weight.
Guys who do it fast, drop a ton of water tend to get less performance decrement than those who do extended diets. As long as the dehydration doesn’t exceed 5% of bodyweight things should be fine. And you may find an improvement in power:weight ratio (which can only be good).
excessive periods of dieting cut into recovery, performance suffers
weight loss > 5% total weight causes problems too
but if you’ve got someone who has a few quick pounds to lose and that’s a small %age of his bodyweight, he may very well find that performance improves. no strenght loss + lighter weight = better ratio
For instance if the body becomes more efficient as utilizing stored fat as a fuel, does this impact on the ability to produce energy through anaerobic glycolysis or is the effect limited to daily functions and repair?
Thanks
this is an intersting question and I’m going to rely on a study in endurance cyclists to address it. the idae of fat adaptation has been one of great interst for about 30 years. I won’t detail all of the work unless folks really want me to but a series of recent studies has done something along hte lines of
5 days of fat adaptation
1 day carbload
test performance
again, this is in endurance cyclists using various performance tests (of varying validity)
the idea is taht you fat adapt and then reload glycogen. in premise, you get teh best of boht worlds, more fat oxidation during exercise but sufficient glycogen to sustain the higher intensity bits (sprints, hills, etc)
data is classically mixed, on average there is no performance gain. however, when you look at the individual data something intersting shows up
the folks who do best on high carbs, do terribly on lowcarbs
the folks who do worst on high carbs usually improve after fat adaptation
other unrelated research has found that there is a genotypic/phenotypic response to diet; some people seem better ‘geared’ to oxidize fat for fuel and I suspect this explains the difference
howver, the most recent study used the same design and tested a time trial (as did the others) but with the additino of several short sprints during the time trial. previou studies only tested time to exhaustion or whatever, which isn’t indicative of real world racing
the study found that sprint performance was hurt as the athletes had lost the ability to generate energy anaerobically (via pyruvate dehydrogenase).
now, PDH is one thingthat changes with diet, adaptation to lowcarbs decreaess teh active form, refeeding with carbs eventually increases the active form. PDH has to be active for folks to use glycogen for fuel anaerobically so the above all makes sense
however, PDH in skeletal muscle will upregulate in about 24 hours of carb-refeeding (liver comes back online in about 5 hours)
so studies that did the refeed the day before the performance test might have gottn a weird false negative
one of the diet books I wrote (ultimate diet 2.0) is similar to what I described above, 4 days lowcarbs,3 day carb load. I wrote it for obsessed physique types but some endurance guys have used it (so have some PL’s and OL’s to lose fat and set PR’s)
the endurance guys who performed best made sure to srart carb-loading on Thursday for a Saturday race. several reported big time PR’s (one took 3-4 mintues off his best 25k cycling time trial). the key in my mind was that the carb load started early enough to get PDH back to clicking but not so early that the fat adaptations were lost (they typically sustain for at least a copule of weeks as I recall)
how’s that for a wordy answer?
Lyle
The wordy answer was actually quite concise and very helpful, thanks Lyle 
Just a few questions regarding it.
-
Is the accute water loss you described intracellular, I guess related to the storage of glycogen, or extracelular? How do methods differ?
-
To what extent is PDH upregulated in the 24hr window and what impact does exercise play in PDH levels in muscles?
-
With regards to the depressed sprint abilty; would it be reasonable to assume that a consistent intake of carbs, over the course of a training week, is advisable to not only recover from intense sprint work outs but to also to perform them to a high standard as well?
Thanks again!
Both are involved. Insulin causes teh kidney to resorb water so there will be a loss of total body water (and minerals, which must be replaced) bcause of it
I don’t understand the last question
- To what extent is PDH upregulated in the 24hr window and what impact does exercise play in PDH levels in muscles?
As I recall, PDH will be at 100% normal after 24 hours of carb loading but don’t swear me to that. I’d have to dig into some research to say for absolute sure.
PDH probably adapts to certain kinds of training (primarily in terms of being able to mobilize energy glycolytically) but, again, I’d have to dig into some research to tell you much more than that.
- With regards to the depressed sprint abilty; would it be reasonable to assume that a consistent intake of carbs, over the course of a training week, is advisable to not only recover from intense sprint work outs but to also to perform them to a high standard as well?
keep in mind that these were ‘sprints’ in the context of cycling. which is like 1 minute or so. The relevance of that to track sprinting, which is relying on a totally different energy pathway (ATP/CP with a touch of glycolysis, depending on the distance of course) is debatable.
for the most part, I think that carb recommendations for strenght/power atehltes are too high. Most sports nutritionists appear to be runners with an RD and they uncritically assume that the carb requirements for an athlete doing 2-6 hours of continuous activity applies to an athlete who may do 10 mintues of total work (due to long rests) over the course of 2 hours.
Of course, total caloric reqirements are generally LOWER in strenght/powr athletes as well. IMO, carb intake should scale accordingly Of course, changes in body composition should be the determining factor, you want the athlete to recover/adapt without getting fat(ter).
A 100m sprinter isn’t using a ton of glyogen, they aren’t relying heavily on glycolysis for most of their training. So how many carbs do they honestly need to fuel training? Not that many, especialy not compared to say a cyclist who may be depleting whole body glycogen on a day to day basis.
Which isn’t to say that I think they should go strictly low-carb. that’s at the other extreme (my comments in earlier posts were about the idae of fat adatpation or using lowcarbs during certain phase of training).
Ketosis can cause dehydration, there is the potential for joint problems (esp with high imapct activities) and not everybody functinos well on very low carbs. The mineral exretion could cause cramping which would be bad.
A happy medium would be a low-moderate amount of carbs, sufficient to avoid ketosis (this requires 100-120 g/day plus whatever is being burned during activity). Plenty of lean protein and the rest from dietary fats to ensure sufficien calories would be the best way to approach it IMO.