Glycogen Depletion.

[LEX-UA]

In the process of arguing with a friend on the topic of glycogen depletion, I realized that I understood the point I was trying to get across but not how to say it exactly. I'm not sure that I was right, of course..that's why I'm here. She randomly spouted out a few words in conversation that I simply couldn't let go. "Within 30 minutes of weight lifting, your glycogen stores are depleted." I stopped her right there, and told her she was wrong that it takes much longer than this. My understanding is as follows:

Aerobic ATP production --> fatty acids, glucose, glycogen --> limiting factor for ATP = inadequate oxygen extraction, or in an endurance athlete's case, glycogen depletion.

Anaerobic ATP production --> glucose, glycogen --> limiting factor for ATP = lactic acid buildup followed by muscle inhibition.

Phos****en system --> Creatine phosphate, stored ATP --> limiting factor for ATP = well, not much of either is stored in the muscle, maybe enough for ~10 second max effort.

Glycogen depletion generally takes between 60-180 minutes. With that being said, I understand glycogen depletion in a marathon runner's case, but is it possible in other forms of exercise? Hypothetically speaking, if someone were to hold a 10lb bar and curl slowly (maybe 40-50% effort, low intensity, below region of anaerobic threshold) and consistently produced ATP aerobically, would glycogen depletion occur after 60-180 minutes? It seems to me that regardless to weight, whether it be 5, 10, or 20 lbs the muscle would begin to 'burn' after X amount of time, signaling lactic acid buildup. BUT lactic acid is a byproduct of ANAEROBIC ATP production and if one were to remain aerobic why would it be present?

Also, given that weight lifting is generally an intense activity and lactic acid inhibits muscle contraction past a certain point, forcing a break, wouldn't it take hours to deplete glycogen?

I think at this point I'm just confusing myself

[Opies]

60 minutes is awfully low.

You don't want complete aerobic activity as that will promote the utilization of fatty acids, but you don't want anaerobic activity which will not use up enough glycogen. Typically when trying to deplete glycogen for say, a cyclic diet, the person will perform 2-3 hours of weightlifting split into two or three sessions (due to exhaustion /lactic acid buildup as you mentioned), and using the 12-20 rep range. Full body workouts would typically work best for this. Your friend is certainly wrong in suggesting glyocgen can be depleted within 30 minutes. In no circumstance is that possible. But the time does vary based on the intensity of workouts since glycogen depletion is based on rep/sets done, not time spent standing around in the gym. I think lyle mcdonald has a list of muscles and how much work they need to do to become glycogen depleted. Smaller groups like bis/tris/delts/calvesetc taking 10-12 sets while large muscles like quads might take up to 20 work sets to become depleted but I'm not too sure on those numbers

[crupiea]

I was training for a marathon a couple of years ago. My short runs were between 5-7 miles 3 times per week and my long runs were 13 and up.

I was also doing starting strength at the same time.

After a couple of months of this i was going for an 24 mile run and after about 16 miles i started feeling like i was running backwrads. I honestly felt like I was no longer moving forward and even though i was aware of what was going on i still didnt feel likle I was mpoving even though my legs were moving. There were no windows or anyhting to see my reflection in to verify it so i was left with just imagination.

Then I started feeling like i was hunched over like an old lady and still not moving forward. After about a mile or two of this i decided to walk for a bit and get myself together.

i sat down on the side of the trail and just broke down crying for no reason. Its not like I was sad or anyting, it just came over me.

i must have been an odd sight to see.

I sat for a few minutes and tried to get started again but the same backward feeling came over me again.

I decided to walk the rest of the way.

i had to walk 6 miles to get back to my car. It was far worse then running.

Now thats what i would call glycogen depletion.

[DJAuto]

In the process of arguing with a friend on the topic of glycogen depletion, I realized that I understood the point I was trying to get across but not how to say it exactly. I'm not sure that I was right, of course..that's why I'm here. She randomly spouted out a few words in conversation that I simply couldn't let go. "Within 30 minutes of weight lifting, your glycogen stores are depleted." I stopped her right there, and told her she was wrong that it takes much longer than this. My understanding is as follows:

Aerobic ATP production --> fatty acids, glucose, glycogen --> limiting factor for ATP = inadequate oxygen extraction, or in an endurance athlete's case, glycogen depletion.

Anaerobic ATP production --> glucose, glycogen --> limiting factor for ATP = lactic acid buildup followed by muscle inhibition.

Phos****en system --> Creatine phosphate, stored ATP --> limiting factor for ATP = well, not much of either is stored in the muscle, maybe enough for ~10 second max effort.

Glycogen depletion generally takes between 60-180 minutes. With that being said, I understand glycogen depletion in a marathon runner's case, but is it possible in other forms of exercise? Hypothetically speaking, if someone were to hold a 10lb bar and curl slowly (maybe 40-50% effort, low intensity, below region of anaerobic threshold) and consistently produced ATP aerobically, would glycogen depletion occur after 60-180 minutes? It seems to me that regardless to weight, whether it be 5, 10, or 20 lbs the muscle would begin to 'burn' after X amount of time, signaling lactic acid buildup. BUT lactic acid is a byproduct of ANAEROBIC ATP production and if one were to remain aerobic why would it be present?

Also, given that weight lifting is generally an intense activity and lactic acid inhibits muscle contraction past a certain point, forcing a break, wouldn't it take hours to deplete glycogen?

I think at this point I'm just confusing myself

Glycogen reservoirs progressively lessen at the 30 minute mark, but there is no reason to believe that a individual who exercises will have maximal depletion at the 30 minute mark.

See here: http://www.uoguelph.ca/hhns/grad/cou...lnickHuman.pdf.

[LEX-UA]

Thanks for the replies and the pdf. file. Very helpful.

Crupiea- sounds like you hit a major wall.


So, glycogen depletion can only occur through aerobic exercise, because one cannot train anaerobically long enough to do so (due to build up lactic acid and other waste)?

[mikevall]

Thanks for the replies and the pdf. file. Very helpful.

Crupiea- sounds like you hit a major wall.


So, glycogen depletion can only occur through anarobic exercise, because one cannot train anaerobically long enough to do so (due to build up lactic acid and other waste)?

its probly both anarobic and aerobic, deffinately not weight training tho, in 30 mins? thats retarded

[LEX-UA]

its probly both anarobic and aerobic, deffinately not weight training tho, in 30 mins? thats retarded

I meant aerobic.
Fixed.

[trainforyou]

While I agree with everything stated previously, I feel it necessary to point out that we are never using ONLY one energy system we are only using one predominant one at a time. So yes while you may be anaerobic during a lift you are still utilizing your aerobic and immediate/atp energy systems too. I won't be so bold as to state with absolute certainty that glycogen depletion is guaranteed during a 10 lbs curl but hypothetically were you to continue the set long enough and repeatedly the glycogen would have to be mobilized from intramuscular and intrahepatic stores. But at no point have I ever heard of glycogen depletion in as little as 30 minutes unless you are already in a depleted state.

[kennycroxdale]

Glycogen reservoirs progressively lessen at the 30 minute mark, but there is no reason to believe that a individual who exercises will have maximal depletion at the 30 minute mark.

See here: http://www.uoguelph.ca/hhns/grad/cou...lnickHuman.pdf.

This website is a dead end.

Little Glycogen Burned

Very little glycogen is burned in 30 minutes under any condition.

The chart in this article demonstrates that.

Does the Fat Burning Zone Really Burn Fat Faster?
http://sportsmedicine.about.com/od/E...Fat-Faster.htm

Calories Burned Low Intensity (60-65% MHR) High Intensity (80-85% MHR)
Total calories burned per min. 4.86 6.86
Fat calories burned per min. 2.43 2.7
Total calories burned in 30 min. 146 206
Total fat calories burned in 30 min. 73 82
Percentage of fat calories burned 50% 39.85%

Doing The Math

Based on the information above that means...

1) Low Intensity burned 18.25 grams of carbohydrate/glucose (Total Calories 146 - 73 Fat Calories = 73 Glucose Calories/4 = 18.25)

2) High Intensity burned 30.75 grams of carbohydrate/glycogen (Total Calories 206 - 82 Fat Calories = 124 Glucose Calories/4 = 30.75)

High Carbohydrate Diets & Post Carbohydrate Reloads

When you examine how much glucose is burned in an exercise program, it high carbohydrates diets and high post carbohydrates reload don't make much sense.

High carbohydrates also make you body more dependent on glucose use, rather than fat.

Kenny Croxdale

[kennycroxdale]

I was training for a marathon a couple of years ago. My short runs were between 5-7 miles 3 times per week and my long runs were 13 and up.

I was also doing starting strength at the same time.

After a couple of months of this i was going for an 24 mile run and after about 16 miles i started feeling like i was running backwrads. I honestly felt like I was no longer moving forward and even though i was aware of what was going on i still didnt feel likle I was mpoving even though my legs were moving. There were no windows or anyhting to see my reflection in to verify it so i was left with just imagination.

Then I started feeling like i was hunched over like an old lady and still not moving forward. After about a mile or two of this i decided to walk for a bit and get myself together.

i sat down on the side of the trail and just broke down crying for no reason. Its not like I was sad or anyting, it just came over me.

i must have been an odd sight to see.

I sat for a few minutes and tried to get started again but the same backward feeling came over me again.

I decided to walk the rest of the way.

i had to walk 6 miles to get back to my car. It was far worse then running.

Now thats what i would call glycogen depletion.

High Fat Diets

Being an endurance athlete, you're probably familiar with this.

Some endurance athletes are employing high fat diets with low to moderate carbohydrate consumption.

The higher fat diet increase the use of fat for energy over glycogen.

Thus, you have more "Glycogen Reserve" later in your runs.

Kenny Croxdale

[kennycroxdale]

60 minutes is awfully low.

You don't want complete aerobic activity as that will promote the utilization of fatty acids, but you don't want anaerobic activity which will not use up enough glycogen. Typically when trying to deplete glycogen for say, a cyclic diet, the person will perform 2-3 hours of weightlifting split into two or three sessions (due to exhaustion /lactic acid buildup as you mentioned), and using the 12-20 rep range. Full body workouts would typically work best for this. Your friend is certainly wrong in suggesting glyocgen can be depleted within 30 minutes. In no circumstance is that possible. But the time does vary based on the intensity of workouts since glycogen depletion is based on rep/sets done, not time spent standing around in the gym. I think lyle mcdonald has a list of muscles and how much work they need to do to become glycogen depleted. Smaller groups like bis/tris/delts/calvesetc taking 10-12 sets while large muscles like quads might take up to 20 work sets to become depleted but I'm not too sure on those numbers

Nice post.

Kenny Croxdale

[Bob808]

Last summer I did a triathlon of a 1.9 mile swim, 38 mile bike, 9.3 mile run. I only ate a banana before the swim started. I was under the impression that there would be sports drinks and fruit available during the event----not so much so Fortunately ONE of the drink stands along the bike route was also handing out these glucose gel tubes that you squeeze in your mouth (cinnamon and honey flavored). The bike route took 3 laps around the lake we swam in. So I got a few gels tubes on each round. I added up and I believe I took in 880 calories of sugar with these. So that gave me about 1000 calories with the banana of pure carbs pretty much.
On the run, I was dragging. Crupiea mentioned running hunched over like an old lady. I was a little bit like that. I had to run about 2 electrical pole lengths for every one I walked during the last 5 miles or so. It sucked. I don't know if I "hit the wall" with glycogen depletion or what, but total exercising time was 5 hours 25 minutes to finish, and I guarantee I was at the anaerobic threshold during a lot of the swim and the run at least, so I'm sure I was hitting a lot of carb use in the body. I weighed 195 which is actually kinda big for a triathlon. Some of those guys were amazing--3:40 to 3:45 finishers. Might have been pros or high level amateurs at least. I had 25-40 lbs on those guys though.

I don't know what I would have done without those gel tubes--thank goodness that church group at that water station had those. I've never passed out or had to quit a physical event before, but that was the longest thing I've ever done, and take away 880 good calories that I needed of an event that probably burned 5000 or so calories, and I would have been toast I fear.

[DJAuto]

This website is a dead end.

That's because I posted it 4.5 years ago, when it wasn't a dead end.

[perpendicularis]

High Fat Diets

Being an endurance athlete, you're probably familiar with this.

Some endurance athletes are employing high fat diets with low to moderate carbohydrate consumption.

The higher fat diet increase the use of fat for energy over glycogen.

Thus, you have more "Glycogen Reserve" later in your runs.

Kenny Croxdale

Yeah thats interesting

http://www.smh.com.au/lifestyle/diet...13-103fun.html

"Becoming “fat adapted” takes time and can be a demanding process"