Glycogen depletion maximizes training??

Glycogen depletion is a training stimulus. However interesting the above study may be, the design is faulty for testing the effect of glycogen depletion--there is lot more going on during recovery than repletion of fuel stores.

The study shows that training an hour twice a day every other day with an hour of recovery time while fasting is a more potent training stimulus than training an hour every day.

"...seven healthy untrained men performed knee extensor exercise with one leg trained in a low-glycogen (Low) protocol and the other leg trained at a high-glycogen (High) protocol."

I don't really think such a study can have much relevance on elite runners. What kind of exercise is that?? And n=7, are they kidding!? It's amazing this was even published.

I was actually thinking about the same thing the other day. Wouldn't it be better to run 2 hours straight one day, rest the next, then run 2 hours again than to just run one hour each of the days? I realize that this is probably not an ideal training plan, but it seems to me that the 2 hour system would be more effective: faster recovery and a more intense stimulus to the system.

My first thought on reading the initial post was:

How ON EARTH does one test a "low glycogen" and "high glycogen" protocol on seperate legs of the same person during the same time period??

Yes, the 2nd session of the day for "low" leg was performed on a somewhat (compared to the first session) depleted state. But......after a day's rest, the first session of the day for the "low" leg was possibly performed in a higher-than-the-"high"-leg glycogen state, right?

Really they should have tested different people at the same time, or the same people at different times (and the test/protocol could have been: measure glycogen levels, and then train. The group who was training at lower levels each time would be compared against the group training at higher levels. And to get the participants to be at those different levels, I would assume that the "low" group would need to eat less carbs after working out. Maybe the next morning, usually considered a later than ideal time to best restore glycogen levels, the "low" people could eat the same calories that the high people ate. Thus: same calories(possibly even same exact diet), but lower starting glycogen levels, and sam training. That would be a better test I would think. Or, one group could simple for a few weeks with lower carbs, thus training at lower glycogen levels, and see how they respond. Either way, this test was indeed flawed for what it proposed to measure. BUT......the 2 a days vs once every day thing was interesting. I remember Al Salazar when he was training for Comrades said he trained reall HIGH miles ever other day. Something like 30-40 miles every other day(in singles). But that of course made sense because he was training for a 50+ mile race. But I wonder if marathoners chose to run 40 every other day, as opposed to 20 every day they would do better. Hmmmm........).

>>>What kind of exercise is that?? And n=7, are they kidding!? It's amazing this was even published

With statistical packages it extremely hard to get a significant result to p<0.05 (p < 0.05 meaning only a 5% chance that the result could be false, so it is strict) with low subject numbers because of a lack of power in the study. In a study with with low numbers these statistical package are very sensitive to variablity even if it found with only one or two subjects and as a result, in many cases, will make the study non-significant even if there are huge changes. So if a significant result is found with n=7 it's usually pretty right, otherwise such a prestigious journal would not accept them. Hard to find physiology subjects as many of them require muscle biopies hence these studies are usually performed with low subject numbers. I have a study printed in the "Journal of Applied Physiology" and getting subjects who were willing to undergo muscle biopises wasn't easy (my study found a 20% decline in in-vitro Ca2+ release, which has a direct relationship to muscle force, with prolonged cycling to fatigue at 75% VO2 peak...amounted to a 26-34% decline in muscle force tested on a cybex).

I am not sure, but couldn't this study be related to food consumption before a run. One would be led to believe that if you go on a 12 mile run without eating before hand you would depend more on fat once some glycogen has been depleted. On the other hand if you eat before the run, your body could use that energy (sugar). Basically my thought is that if you don't eat before you run (morning run), your body will be able to have more endurance after a period of training in this manner. I have no idea if this is correct, but let me know if it is.

I am not positive either, but, from what I remember, there was one study that I read where 2 groups of athletes did the same type of training, and ate the same diet. BUT.......they ate a lot of their calories (mostly carbs) at different TIMES. One group immediately after working out, the other group fairly soon BEFORE working out. Apparently (again, from what I remember), the group eating a big chunk of carbs RIGHT AFTER their workouts had higher levels of muscle glycogen, and better endurance, than the group who ate those same big chunk of carbs (same amount as first group) right before their workouts. The reason why this was? Apparently it has been demonstrated that one should replenish glycogen stores (if the goal is to have high levels, which it usually is) ideally within a few hours of working out. Some studies show the ideal window of time is only 30 minutes post workout, some other recent studies show a much longer window, basically several hours. But I think the studies concur that if you don't eat many carbs after working out, and wait until the morning for your biggest carb-meal (pre workout as opposed to post) of the day, your glycogen stores will be lower.

SO........that is a long way of saying: if one wanted to test the idea of training on lower glyocen levels vs higher levels (but still eating same amount of calories), then 2 ideas would be:

1) Have one group could eat less carbs (but more fat/protein) than another group , but same calories, thus reducing glycogen stores, or....

2) (if one wanted to have no difference in composition of diet between comparison groups) have only the TIME of day the carbs ingested be different: again, one would ingenst lots of carbs post workout when glycogen replenishment is better, and one ingenst lots of carbs pre-workout.

Anyway, those are my thoughts. (and to directly answer your question "another runner": not eating carbs before run might not effect glycogen stores as much as you think, if one had eaten a lot of carbs post workout from the day before. So the only way to SIGNIFICANTLY reduce glycogen stores, if that was your goal, would be to eat less carbs period. Very few post workout, and very few pre-workout, and do lots of training. You would definitely be training on glycogen depleted muscles at that point, but most would NOT reccommend that on a regular basis. But possibly occasional doses of a few days here and there training on glycogen-depleted legs might induce a training repsonse, as Phoenix I think was saying was possible. But I am not sure how/why that would work, other than being an added stress to your training)

Phoenix? Others?

One thing to point out in this is that the research group was not espousing this as a training plan, but taking a first step towards investigating IF and HOW glycogen depletion may trigger some of the adaptations that occur w/ endurance exercise.

Their working hypothesis is that some transcription factors are actually bound to glycogen and these factors MAY become released when glycogen levels are low.

FWIW, this is an excellent lab group and Bengt Saltin is one of the co-authors. That doesn't ensure a tight study, but I've read the whole thing and the methodology is sound.

Phoenix's point about what the study definitively proves is correct, as is the point about them using untrained individuals. As I said, however, this was an initial step in this group to evaluate the premise that glycogen levels are mechanistically linked to training adaptations.

IF they're right, it opens up some interesting observations and questions, some of which have already been presented on this board. For example, IF this is correct it may ultimately suggest that two a days are not as good as one longer run since the longer run would deplete glycogen more readily.

The authors themselves state that coaches should not use these data to start altering training. I concur and I know we can't make conclusions yet. I've published in JAP and other journals and am well aware of what individuals studies prove and don't prove. However, I think one of the fun and intriguing things to do is speculate on the implications of hypotheses such as this one.

Lance-a-lot-

Actually, what you are a proposing would be one of the next questions to ask, not necessarily what they should have done first.

IF glycogen levels seem to influence the adaptive response to training, THEN the next questions to ask would include

"What if I manipulate my glycogen levels by going on a low-carb diet?"

That's actually an excellent question. If someone on the zone diet has lower muscle glycogen, do they get more benefit doing the same amount of mileage as someone ingesting a high CHO diet.

OR

Does the runner with the high CHO diet do better because they are able to consistently achieve a higher intensity and/or duration of training.

OR

Is it a wash??

Good stuff.

macker wrote:

For example, IF this is correct it may ultimately suggest that two a days are not as good as one longer run since the longer run would deplete glycogen more readily.

A working athletes approach to 2-a-day is generally before and after work. Theres not much alternative really.

However, if you read journals from kenyan training camps, the first session (shortish run) is done at 6am followed by b'fast and the main training is at 10am. With the recovery so short they are effectively doing their heavy training on a relatively low-glycogen system. No?

wannabekila wrote:

A working athletes approach to 2-a-day is generally before and after work. Theres not much alternative really.

However, if you read journals from kenyan training camps, the first session (shortish run) is done at 6am followed by b'fast and the main training is at 10am. With the recovery so short they are effectively doing their heavy training on a relatively low-glycogen system. No?

No doubt that logistically 2 a days are the only way to get in good miles. I do it myself when I'm time limited or especially when I'm worn out.

Great point about the Kenyans. IF (and we're still talking theoretically here) the hypothesis is correct, then they may have stumbled on to a great way to maximize their work.

macker wrote:

[quote]wannabekila wrote:

IF (and we're still talking theoretically here) the hypothesis is correct, then they may have stumbled on to a great way to maximize their work.

'stumbled' may be a touch patronising here. Just because they dont have advanced scientific proof doesnt mean they didnt know it empirically already?

Point taken. My choice of words meaning they didn't do controlled studies, not that they weren't based on thoughtful observations.