Dispelling some exercise myths around glycogen and fat burning
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So there are some things I just read. Both are from websites that deal with diabetes so this excess BG stuff is defintely related to some kind of insulin resistance thingy.
So one website confirmed what I was saying. Intense exercise release a lot of stress harmones: epinephrine, norepinephrine, cortisol, glucagon, and growth hormone. All of these will encourage the production of BG and some counter the effects of harmones that are signaled to build things (like building glycogen and building triglycerol and building proteins, ect).
In this website, they say that repeated training of the same form of exercise will lessen the effects of the body releasing the stress harmones. So maybe the first time you do sprints will cause a lot of BG to build. The 50th time you do the exact same sprints, then eh! no big deal. You body learns and knows better and won't go crazy on the stress harmones. Therefore less BG buildup for the same level of exercise. The same website suggests that you not eat as much before you exercise. But duhhhh! What if you want to run because you just ate a bunch of stuff?
Thus brings me to the second website that I just read. So in addition, if you eat a bunch of carbs, the natural reaction is for extra insulin to get released from the pancreas into the blood. Higher insulin means more knocking on the door so more glucose can enter into cells. But you have insulin resistance so the insulin receptor is asleep when insulin knocks on the door so glut-4 cannot come and let glucose in.
Well, the second website makes a point that when stress harmones begin to increase, if there is already low amounts of insulin in the blood, then this can sometimes cause the insulin resistance (probably because not enough insulin is going around knocking on muscle cells doors). So this website says to check your insulin level before doing exercise. If the insulin level is too low, wait to perform strenous exercise. Eventually, insulin levels will rise to respond to the food you just ate. (although T1 diabetes is caused by the pancrease not releasing enough insulin- I assume if you have this, then you already know what to do and you don't need me to explain this) But if you have T2 or some other IR problem, then you just have to wait for insulin levels to rise, then when you do exercise, there is already higher levels of insulin working when the stress harmones get dumped in as well. So the exercise will make those particular muscle cells become more sensitive to the insulin and thus become more reactive to the BG.
I don't know. The best I can do from Dr. Google.
Edited because I don't know the difference between conformed and confirmed. Or I just typed an o when I meant to type an i the first time around.0 -
Apologies if I remember wrong -- did you post eaerlier that you have insulin resistance ?ForecasterJason wrote: »So, to summarize my earlier question: What would be the best way from an exercise standpoint to remove excess circulating glucose (though not necessarily stored body fat)?
If so be very careful in taking any advice here, from people who are either relaying personal experience or passing on general advice for healthy people.
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Yes, but it's inconclusive (based solely on the A1C test). Additionally, if I really do have it, it's at an early stage based on the reading. My doctor wasn't too concerned. All he wanted me to do was get more exercise and watch my sugar intake.ericGold15 wrote: »
Apologies if I remember wrong -- did you post eaerlier that you have insulin resistance ?ForecasterJason wrote: »So, to summarize my earlier question: What would be the best way from an exercise standpoint to remove excess circulating glucose (though not necessarily stored body fat)?
If so be very careful in taking any advice here, from people who are either relaying personal experience or passing on general advice for healthy people.0 -
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So there are some things I just read. Both are from websites that deal with diabetes so this excess BG stuff is defintely related to some kind of insulin resistance thingy.
So one website confirmed what I was saying. Intense exercise release a lot of stress harmones: epinephrine, norepinephrine, cortisol, glucagon, and growth hormone. All of these will encourage the production of BG and some counter the effects of harmones that are signaled to build things (like building glycogen and building triglycerol and building proteins, ect).
In this website, they say that repeated training of the same form of exercise will lessen the effects of the body releasing the stress harmones. So maybe the first time you do sprints will cause a lot of BG to build. The 50th time you do the exact same sprints, then eh! no big deal. You body learns and knows better and won't go crazy on the stress harmones. Therefore less BG buildup for the same level of exercise. The same website suggests that you not eat as much before you exercise. But duhhhh! What if you want to run because you just ate a bunch of stuff?
Thus brings me to the second website that I just read. So in addition, if you eat a bunch of carbs, the natural reaction is for extra insulin to get released from the pancreas into the blood. Higher insulin means more knocking on the door so more glucose can enter into cells. But you have insulin resistance so the insulin receptor is asleep when insulin knocks on the door so glut-4 cannot come and let glucose in.
Well, the second website makes a point that when stress harmones begin to increase, if there is already low amounts of insulin in the blood, then this can sometimes cause the insulin resistance (probably because not enough insulin is going around knocking on muscle cells doors). So this website says to check your insulin level before doing exercise. If the insulin level is too low, wait to perform strenous exercise. Eventually, insulin levels will rise to respond to the food you just ate. (although T1 diabetes is caused by the pancrease not releasing enough insulin- I assume if you have this, then you already know what to do and you don't need me to explain this) But if you have T2 or some other IR problem, then you just have to wait for insulin levels to rise, then when you do exercise, there is already higher levels of insulin working when the stress harmones get dumped in as well. So the exercise will make those particular muscle cells become more sensitive to the insulin and thus become more reactive to the BG.
I don't know. The best I can do from Dr. Google.
Edited because I don't know the difference between conformed and confirmed. Or I just typed an o when I meant to type an i the first time around.
Thank you so much, and for your execellent earlier post on this! I don't know why people who write for diabetic folks act as if we only have a seventh grade reading level, lol. This might not be perfect (I don't know about energy cycles and that sort of biology), but it's far better than anything I've read.
Most of my doctors have said I don't need to sprint. Duh. Nobody needs to sprint. But the science there with diabetics looks good (about the overall benefits, not what we were discussing), and my really fast dog loves it, as do I, so I want to sprint. My levels aren't frightening at all, either, so Forecaster Jason and I are the ones who don't get a lot of in-depth info about our IR. Most is easy enough to figure out from other sources, but this was a bit of a conundrum.
There are definitely diabetics who don't need to be sprinting! But their levels go crazy high and start crazier than mine (and Forecaster Jason's, from his stated level). Or they stay up all day from certain kinds of exercise, which is a different problem to have.0 -
matsprt1984 wrote: »
This is fun...
Educational :-)
Think I only bonked once. Always thought there should be more signals (drop in performance, craps, etc) but remembered it was a sudden drop (25 years ago so memory kind of fuzzy; stopped regular exercise until this year). Done a few centuries this year with craps and slow crawls here and there, but didn't bonk. Maybe the difference is the short breaks (10-20 minutes) after 2-3 hours of riding, verses 5+ hours of continuous riding when I hit the wall. At most I'm only eating 600-1000 calories on my centuries which is ~1/3 or less of total expenditure at 0.75-0.80 IF (Nominal Power/FTP) for 5.5-6 hours active. I'm thinking my muscle glycogen should have been completely depleted but ???0 -
rankinsect wrote: »
actual way to burn the most fat is to burn the most total calories, regardless of where the calories come from, because in the long term the source of the energy is irrelevant.
With this quote in mind can you explain why people prefer HITT over running?
and lets be honest for every article that I see that HITT is better for weight loss, I see the same number of articles that say running for long periods of day is better for weight loss.
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There are very few sports that can truly benefit from HIIT and running is one of them. HIIT is a regimen (routine - do this for... and that for... at this level of intensity...). It's a tool for competition that sharpen and/or peak for explosive power in the final meters. Per unit of time, HIIT does expend a large amount of energy; however, the resultant fatigue limits the total duration per session. The short-termed fatigue (7 days) it generates limits the number of times that the training can be done to two or three times a week for 6-8 weeks consecutively (long-term fatigue, 42 days, also know as form). One's warm-up/cool-down session by themselves will expend as much if not more energy. That is if the session is performed as DESIGNED, upwards of 170% VO2Max. For thirty or so minutes are you expending more energy by going at the pace slightly higher than the recommended intensity level (very low) for warm-up and cool-down? YES. Is 30 minutes enough stimulus to enhance your aerobic engine? Probably not, at least for cycling.
Duration and intensity are the two primary factors in the energy side of the equation. Other to note is the type of activity and the environmental conditions. Take your pick, go harder but in less time or the reverse if time is not a factor. The first method is typically how most elite athletes build their aerobic engine, ie miles build champions.
One can argue that originator(s) was lazy on the name choice but they capitalized the words. Some folks just like to take this out of context and call any intervals training (intensity is relative) as HIIT. (To make a quick $ and for the participants, hoodwinked. But laziness and pride comes in mind when they don't even question the bases of what they are doing.) Fine, just don't capitalize it.0 -
Commander_Keen wrote: »rankinsect wrote: »
actual way to burn the most fat is to burn the most total calories, regardless of where the calories come from, because in the long term the source of the energy is irrelevant.
With this quote in mind can you explain why people prefer HITT over running?
and lets be honest for every article that I see that HITT is better for weight loss, I see the same number of articles that say running for long periods of day is better for weight loss.
Because you need more articles to convince people to buy HIIT videos or buy HIIT plans. Running long periods? Well there are books and training plans that will get a newbie runner to running a marathon in only 18 weeks (which I disagree with btw). And you want to do that because look at all the weight you could lose training for that marathon (not to mention the expensive shoes you will need to buy every 3 months).
A more realistic answer: Time. People either have busy schedules or low interest to spend more time for exercising. If I told you that you could burn 200 calories in 20 minutes or 500 calories in an hour? Which one would you pick? Many people would pick the 20 minute workout. That is what HIIT gives you. More bang for those 20 minutes. But if you slow it down and go longer, you could burn even more calories. So there is truth to be told from both point of views. How you present the information to the reader depends on if you are selling a HIIT video or convincing someone that you need to train for a marathon or half marathon.0 -
Side note. If you really want to burn a bunch of fat. Sleep. Sleeping 8 hours will burn most of your liver glycogen within a few hours. The rest of the time you will need to burn stored fat to make up the difference.
But what's really going on as you are sleeping? Your brain and vital organs are using energy (from fat and carbs) and you are not eating anything. Amazing concept. Simple yet powerful. Now apply the same idea for when you are awake for the rest of the 16 hours in the day.0 -
@rankinsect
Great post, well reasoned, and in line with what your norm is. Great timing for me personally too, as this is something I've been working on expanding my knowledge of.ericGold15 wrote: »
Or not. From 'MedFitness, associated with the U of Michigan:.Glycogen isn't used first - the vast majority of exercise is fuelled from a blend of fat and glycogen (carbohydrate) in differing proportions. During lower intensity exercise fat is the predominant fuel, higher intensity carbohydrate is the predominant source. If I remember correctly the 50/50 point is roughly 70% of max HR but sure someone can correct me.Exercising for longer than 30 minutes shifts the primary macromolecules that are metabolized from glucose to fatty acids. Shifting from glucose and glycogen supplies allows the body to efficiently mobilize and utilize free fatty acids (FFAs) derived from lipids in adipose tissue, which resides mainly under the skin.
... ...
After the first 30 minutes of exercise, the body runs out of its glycogen storage and then turns mainly to what is left of the glucose in the blood and then finally to fat and amino acids derived from muscle protein. Supporting evidence of fatty acid release comes from physiologic research where human gluteal fat cells isolated after 30 minutes of biking showed that cathecholamine induced lipolysis had increased between 35-50% 4. If exercise does not last until 30 minutes then fat burning is never achieved because all of the glycogen is not used u p. So while one may be able to prevent adding fat to the body, one is not metabolizing fat from the adipose tissues during the exercise. In short, exercises aerobically for less than 30 minutes, one is just maintaining the adipose tissue status quo and decreasing muscle mass.
A little Googling found numbers that you mention, based on a 1994 study of endurance athletes studied after an overnight fast.
Thanks for the giggles - that article is hilarious!
Running out of glycogen storage after 30 minutes - really?
Think of the burn rate needed to run through approximately 500 grams of carbohydrate in 30 minutes and you will see what nonsense that is.
Think of how far runners can go before they "hit the wall" or how long a cyclist goes before they "bonk". And how awful it feels (crushing and sudden fatigue, mental confusion such as forgetting to put your feet down when you stop pedalling! Yep done that.).
During a 20 minute VO2 max test I went from RER of 0.82 during the gentle start (0.7 is totally fat fuelled) progressively through to RER of 1.0 (totally carb fuelled) after about 15 minutes building to very high intensity and eventually anaerobic at maximal effort / failure.EvgeniZyntx wrote: »ericGold15 wrote: »
Or not. From 'MedFitness, associated with the U of Michigan:.Glycogen isn't used first - the vast majority of exercise is fuelled from a blend of fat and glycogen (carbohydrate) in differing proportions. During lower intensity exercise fat is the predominant fuel, higher intensity carbohydrate is the predominant source. If I remember correctly the 50/50 point is roughly 70% of max HR but sure someone can correct me.Exercising for longer than 30 minutes shifts the primary macromolecules that are metabolized from glucose to fatty acids. Shifting from glucose and glycogen supplies allows the body to efficiently mobilize and utilize free fatty acids (FFAs) derived from lipids in adipose tissue, which resides mainly under the skin.
... ...
After the first 30 minutes of exercise, the body runs out of its glycogen storage and then turns mainly to what is left of the glucose in the blood and then finally to fat and amino acids derived from muscle protein. Supporting evidence of fatty acid release comes from physiologic research where human gluteal fat cells isolated after 30 minutes of biking showed that cathecholamine induced lipolysis had increased between 35-50% 4. If exercise does not last until 30 minutes then fat burning is never achieved because all of the glycogen is not used u p. So while one may be able to prevent adding fat to the body, one is not metabolizing fat from the adipose tissues during the exercise. In short, exercises aerobically for less than 30 minutes, one is just maintaining the adipose tissue status quo and decreasing muscle mass.
A little Googling found numbers that you mention, based on a 1994 study of endurance athletes studied after an overnight fast.
Thanks for the giggles - that article is hilarious!
Running out of glycogen storage after 30 minutes - really?
Think of the burn rate needed to run through approximately 500 grams of carbohydrate in 30 minutes and you will see what nonsense that is.
Think of how far runners can go before they "hit the wall" or how long a cyclist goes before they "bonk". And how awful it feels (crushing and sudden fatigue, mental confusion such as forgetting to put your feet down when you stop pedalling! Yep done that.).
During a 20 minute VO2 max test I went from RER of 0.82 during the gentle start (0.7 is totally fat fuelled) progressively through to RER of 1.0 (totally carb fuelled) after about 15 minutes building to very high intensity and eventually anaerobic at maximal effort / failure.
Agreed, it's ridiculous to talk about "running out of glycogen" without mentioning intensity. Light exercise is basically glycogen neutral. High intensity work (RER 1, preferentially CHO fuelled) will reduce global stores to about 20% in one hr in the trained athlete.
What does the bolded above actually mean? Exercising for less than 30 minutes now suddenly decreases muscle mass?ericGold15 wrote: »In short, exercises aerobically for less than 30 minutes, one is just maintaining the adipose tissue status quo and decreasing muscle mass.
First off, great post @rankinsect
Now, on to my derailment...
Does recent diet have any impact on this conversation? i.e. training fasted vs fed? Or is the idea of fasted training somewhat of a misnomer?
Example, are "depleted glycogen stores" more likely to happen more quickly when training 16 hours after your last meal as compared to 3 hours? Lets assume fairly high intensity cardio for 60-90 minutes.
Anecdotal experience suggests it is so, but some of that may be mental.
This is one I've looked for some info on, and would welcome from those that have a more in depth understanding than I do.
From my basic knowledge, assuming that glycogen stores were properly replenished before any activity as mentioned above, the fasting really shouldn't matter unless it was for example fasting in combination with a high calorie deficit going on. In a normal maintenance state, the glycogen should be restored and available for use.
This might mean depleting glycogen stores quicker if you work out after extended fasts, as the carb and fat fuels are not as readily available, thus the glycogen would be used at a quicker rate to attempt to keep up with the intensity of the workout.Commander_Keen wrote: »rankinsect wrote: »
actual way to burn the most fat is to burn the most total calories, regardless of where the calories come from, because in the long term the source of the energy is irrelevant.
With this quote in mind can you explain why people prefer HITT over running?
and lets be honest for every article that I see that HITT is better for weight loss, I see the same number of articles that say running for long periods of day is better for weight loss.
Because you need more articles to convince people to buy HIIT videos or buy HIIT plans. Running long periods? Well there are books and training plans that will get a newbie runner to running a marathon in only 18 weeks (which I disagree with btw). And you want to do that because look at all the weight you could lose training for that marathon (not to mention the expensive shoes you will need to buy every 3 months).
A more realistic answer: Time. People either have busy schedules or low interest to spend more time for exercising. If I told you that you could burn 200 calories in 20 minutes or 500 calories in an hour? Which one would you pick? Many people would pick the 20 minute workout. That is what HIIT gives you. More bang for those 20 minutes. But if you slow it down and go longer, you could burn even more calories. So there is truth to be told from both point of views. How you present the information to the reader depends on if you are selling a HIIT video or convincing someone that you need to train for a marathon or half marathon.
I would think that even at a level that will call on glycogen stores, a steady state workout at max capacity for the time frame involved would still trump any actual HIIT for calorie burn. Real high intensity would rely on glycogen, but the cardio overload is quick. Even if workload was maintained the aerobic zone, the upper edge of the aerobic zone would trump in calorie burn IMO.0 -
Commander_Keen wrote: »rankinsect wrote: »
actual way to burn the most fat is to burn the most total calories, regardless of where the calories come from, because in the long term the source of the energy is irrelevant.
With this quote in mind can you explain why people prefer HITT over running?
and lets be honest for every article that I see that HITT is better for weight loss, I see the same number of articles that say running for long periods of day is better for weight loss.
Well, I do HIIT, but I don't do it for fat loss, I do it for cardiovascular fitness. My reason for doing that over steady-state cardio: when I researched it, HIIT was the most time-efficient way to get good results (again, the results I want are fitness, not calorie burns). I wanted a workout with a time commitment I was willing to make for the rest of my life, and HIIT fit that need.0 -
rankinsect wrote: »Commander_Keen wrote: »rankinsect wrote: »
actual way to burn the most fat is to burn the most total calories, regardless of where the calories come from, because in the long term the source of the energy is irrelevant.
With this quote in mind can you explain why people prefer HITT over running?
and lets be honest for every article that I see that HITT is better for weight loss, I see the same number of articles that say running for long periods of day is better for weight loss.
Well, I do HIIT, but I don't do it for fat loss, I do it for cardiovascular fitness. My reason for doing that over steady-state cardio: when I researched it, HIIT was the most time-efficient way to get good results (again, the results I want are fitness, not calorie burns). I wanted a workout with a time commitment I was willing to make for the rest of my life, and HIIT fit that need.
This is also something I've been looking into as far as the relationships of building glycogen store capacity to improve in other aspects of workout. As an example @arditarose does primarily weight training. Could HIIT type work help improve glycogen stores in specific areas, and possibly improve her weight training ability due to improvements in that area? I would think so, as any heavy lifting is influenced by both muscle and fuel. But it's still grey area to me due to less research into the matter.
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Commander_Keen wrote: »rankinsect wrote: »
actual way to burn the most fat is to burn the most total calories, regardless of where the calories come from, because in the long term the source of the energy is irrelevant.
With this quote in mind can you explain why people prefer HITT over running?
and lets be honest for every article that I see that HITT is better for weight loss, I see the same number of articles that say running for long periods of day is better for weight loss.
Because you need more articles to convince people to buy HIIT videos or buy HIIT plans. Running long periods? Well there are books and training plans that will get a newbie runner to running a marathon in only 18 weeks (which I disagree with btw). And you want to do that because look at all the weight you could lose training for that marathon (not to mention the expensive shoes you will need to buy every 3 months).
A more realistic answer: Time. People either have busy schedules or low interest to spend more time for exercising. If I told you that you could burn 200 calories in 20 minutes or 500 calories in an hour? Which one would you pick? Many people would pick the 20 minute workout. That is what HIIT gives you. More bang for those 20 minutes. But if you slow it down and go longer, you could burn even more calories. So there is truth to be told from both point of views. How you present the information to the reader depends on if you are selling a HIIT video or convincing someone that you need to train for a marathon or half marathon.
I would also add that some people hate running/steady state cardio. They see HIIT as a viable alternative that still provides a decent calorie burn and cardiovascular benefit.0 -
rankinsect wrote: »Commander_Keen wrote: »rankinsect wrote: »
actual way to burn the most fat is to burn the most total calories, regardless of where the calories come from, because in the long term the source of the energy is irrelevant.
With this quote in mind can you explain why people prefer HITT over running?
and lets be honest for every article that I see that HITT is better for weight loss, I see the same number of articles that say running for long periods of day is better for weight loss.
Well, I do HIIT, but I don't do it for fat loss, I do it for cardiovascular fitness. My reason for doing that over steady-state cardio: when I researched it, HIIT was the most time-efficient way to get good results (again, the results I want are fitness, not calorie burns). I wanted a workout with a time commitment I was willing to make for the rest of my life, and HIIT fit that need.
So you would not use HIIT for weight loss?0 -
robertw486 wrote: »@rankinsect
Great post, well reasoned, and in line with what your norm is. Great timing for me personally too, as this is something I've been working on expanding my knowledge of.ericGold15 wrote: »
Or not. From 'MedFitness, associated with the U of Michigan:.Glycogen isn't used first - the vast majority of exercise is fuelled from a blend of fat and glycogen (carbohydrate) in differing proportions. During lower intensity exercise fat is the predominant fuel, higher intensity carbohydrate is the predominant source. If I remember correctly the 50/50 point is roughly 70% of max HR but sure someone can correct me.Exercising for longer than 30 minutes shifts the primary macromolecules that are metabolized from glucose to fatty acids. Shifting from glucose and glycogen supplies allows the body to efficiently mobilize and utilize free fatty acids (FFAs) derived from lipids in adipose tissue, which resides mainly under the skin.
... ...
After the first 30 minutes of exercise, the body runs out of its glycogen storage and then turns mainly to what is left of the glucose in the blood and then finally to fat and amino acids derived from muscle protein. Supporting evidence of fatty acid release comes from physiologic research where human gluteal fat cells isolated after 30 minutes of biking showed that cathecholamine induced lipolysis had increased between 35-50% 4. If exercise does not last until 30 minutes then fat burning is never achieved because all of the glycogen is not used u p. So while one may be able to prevent adding fat to the body, one is not metabolizing fat from the adipose tissues during the exercise. In short, exercises aerobically for less than 30 minutes, one is just maintaining the adipose tissue status quo and decreasing muscle mass.
A little Googling found numbers that you mention, based on a 1994 study of endurance athletes studied after an overnight fast.
Thanks for the giggles - that article is hilarious!
Running out of glycogen storage after 30 minutes - really?
Think of the burn rate needed to run through approximately 500 grams of carbohydrate in 30 minutes and you will see what nonsense that is.
Think of how far runners can go before they "hit the wall" or how long a cyclist goes before they "bonk". And how awful it feels (crushing and sudden fatigue, mental confusion such as forgetting to put your feet down when you stop pedalling! Yep done that.).
During a 20 minute VO2 max test I went from RER of 0.82 during the gentle start (0.7 is totally fat fuelled) progressively through to RER of 1.0 (totally carb fuelled) after about 15 minutes building to very high intensity and eventually anaerobic at maximal effort / failure.EvgeniZyntx wrote: »ericGold15 wrote: »
Or not. From 'MedFitness, associated with the U of Michigan:.Glycogen isn't used first - the vast majority of exercise is fuelled from a blend of fat and glycogen (carbohydrate) in differing proportions. During lower intensity exercise fat is the predominant fuel, higher intensity carbohydrate is the predominant source. If I remember correctly the 50/50 point is roughly 70% of max HR but sure someone can correct me.Exercising for longer than 30 minutes shifts the primary macromolecules that are metabolized from glucose to fatty acids. Shifting from glucose and glycogen supplies allows the body to efficiently mobilize and utilize free fatty acids (FFAs) derived from lipids in adipose tissue, which resides mainly under the skin.
... ...
After the first 30 minutes of exercise, the body runs out of its glycogen storage and then turns mainly to what is left of the glucose in the blood and then finally to fat and amino acids derived from muscle protein. Supporting evidence of fatty acid release comes from physiologic research where human gluteal fat cells isolated after 30 minutes of biking showed that cathecholamine induced lipolysis had increased between 35-50% 4. If exercise does not last until 30 minutes then fat burning is never achieved because all of the glycogen is not used u p. So while one may be able to prevent adding fat to the body, one is not metabolizing fat from the adipose tissues during the exercise. In short, exercises aerobically for less than 30 minutes, one is just maintaining the adipose tissue status quo and decreasing muscle mass.
A little Googling found numbers that you mention, based on a 1994 study of endurance athletes studied after an overnight fast.
Thanks for the giggles - that article is hilarious!
Running out of glycogen storage after 30 minutes - really?
Think of the burn rate needed to run through approximately 500 grams of carbohydrate in 30 minutes and you will see what nonsense that is.
Think of how far runners can go before they "hit the wall" or how long a cyclist goes before they "bonk". And how awful it feels (crushing and sudden fatigue, mental confusion such as forgetting to put your feet down when you stop pedalling! Yep done that.).
During a 20 minute VO2 max test I went from RER of 0.82 during the gentle start (0.7 is totally fat fuelled) progressively through to RER of 1.0 (totally carb fuelled) after about 15 minutes building to very high intensity and eventually anaerobic at maximal effort / failure.
Agreed, it's ridiculous to talk about "running out of glycogen" without mentioning intensity. Light exercise is basically glycogen neutral. High intensity work (RER 1, preferentially CHO fuelled) will reduce global stores to about 20% in one hr in the trained athlete.
What does the bolded above actually mean? Exercising for less than 30 minutes now suddenly decreases muscle mass?ericGold15 wrote: »In short, exercises aerobically for less than 30 minutes, one is just maintaining the adipose tissue status quo and decreasing muscle mass.
First off, great post @rankinsect
Now, on to my derailment...
Does recent diet have any impact on this conversation? i.e. training fasted vs fed? Or is the idea of fasted training somewhat of a misnomer?
Example, are "depleted glycogen stores" more likely to happen more quickly when training 16 hours after your last meal as compared to 3 hours? Lets assume fairly high intensity cardio for 60-90 minutes.
Anecdotal experience suggests it is so, but some of that may be mental.
This is one I've looked for some info on, and would welcome from those that have a more in depth understanding than I do.
From my basic knowledge, assuming that glycogen stores were properly replenished before any activity as mentioned above, the fasting really shouldn't matter unless it was for example fasting in combination with a high calorie deficit going on. In a normal maintenance state, the glycogen should be restored and available for use.
This might mean depleting glycogen stores quicker if you work out after extended fasts, as the carb and fat fuels are not as readily available, thus the glycogen would be used at a quicker rate to attempt to keep up with the intensity of the workout.Commander_Keen wrote: »rankinsect wrote: »
actual way to burn the most fat is to burn the most total calories, regardless of where the calories come from, because in the long term the source of the energy is irrelevant.
With this quote in mind can you explain why people prefer HITT over running?
and lets be honest for every article that I see that HITT is better for weight loss, I see the same number of articles that say running for long periods of day is better for weight loss.
Because you need more articles to convince people to buy HIIT videos or buy HIIT plans. Running long periods? Well there are books and training plans that will get a newbie runner to running a marathon in only 18 weeks (which I disagree with btw). And you want to do that because look at all the weight you could lose training for that marathon (not to mention the expensive shoes you will need to buy every 3 months).
A more realistic answer: Time. People either have busy schedules or low interest to spend more time for exercising. If I told you that you could burn 200 calories in 20 minutes or 500 calories in an hour? Which one would you pick? Many people would pick the 20 minute workout. That is what HIIT gives you. More bang for those 20 minutes. But if you slow it down and go longer, you could burn even more calories. So there is truth to be told from both point of views. How you present the information to the reader depends on if you are selling a HIIT video or convincing someone that you need to train for a marathon or half marathon.
I would think that even at a level that will call on glycogen stores, a steady state workout at max capacity for the time frame involved would still trump any actual HIIT for calorie burn. Real high intensity would rely on glycogen, but the cardio overload is quick. Even if workload was maintained the aerobic zone, the upper edge of the aerobic zone would trump in calorie burn IMO.
From a scientific point of view, what exactly does this mean? What exactly triggers a particular muscle cell to pick glucose for energy instead of fat or vice versa?
I know if you are in oxygen debt, meaning the mitochondria doesn't have enough oxygen to support Krebs Cycle and ETC, then the muscle cell will need to burn a carb using glycolysis to meet that particular demand for ATP.
But what if oxygen was available? What triggers a specific muscle cell to prefer a fatty acid instead of glucose when both (glucose and fatty acid) are avaialable to the muscle cell?
So when you say a level that will call on glycogen stores, I intepret this to mean any intensity that requires an energy demand that exceeds what the aerobic system can support. So harder than a slow easy run but less intense than what exactly? Steady state workout a max capacity? Maximum what? Vo2Max? max heart rate?
I am not an expert on HIIT but aren't you sort of hitting the maximum capacity for that muscle group for a certain time frame? Even if the time frame was say 20 seconds? Then you move onto another muscle group and work that muscle group for maximum capacity for say another 20 seconds? Then quickly move to another muscle group that is rested and repeat. The sum of all the working of all the different muscle groups without stopping is a form of steady state from the heart's point of view.
So I am just confused as to what you are trying to express. Maybe a more detailed explanation would help?
"Real high intensity would rely on glycogen, but the cardio overload is quick. Even if workload was maintained the aerobic zone, the upper edge of the aerobic zone would trump in calorie burn IMO."
This sentence is conflicting. real high intensity which would rely on glycogen (meaning you have to force the anaerobic system to work harder than the aerobic system)... Even if workload was maintained the aerobic zone. See the oxymoron here? How can you force an intensity out of the aerobic zone but maintain the aerobic zone?
Look up glycolysis, krebs cycle, and electron transport chain.
Unless you are burning fatty acid or amino acid, the use of glycogen in the Krebs Cycle has to start with glycolysis. It's not like glucose can be used and circumvent the anaerobic system of glycolysis. So if you are forcing intensity to use glycogen, I don't know how else that could happen unless you go beyond your aerobic zone. The only way I know to avoid the anaerobic zone is running an intensity that could use fatty acids.
Unless I am missing something here?
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Commander_Keen wrote: »rankinsect wrote: »Commander_Keen wrote: »rankinsect wrote: »
actual way to burn the most fat is to burn the most total calories, regardless of where the calories come from, because in the long term the source of the energy is irrelevant.
With this quote in mind can you explain why people prefer HITT over running?
and lets be honest for every article that I see that HITT is better for weight loss, I see the same number of articles that say running for long periods of day is better for weight loss.
Well, I do HIIT, but I don't do it for fat loss, I do it for cardiovascular fitness. My reason for doing that over steady-state cardio: when I researched it, HIIT was the most time-efficient way to get good results (again, the results I want are fitness, not calorie burns). I wanted a workout with a time commitment I was willing to make for the rest of my life, and HIIT fit that need.
So you would not use HIIT for weight loss?
In general I don't use exercise for weight loss, because I am overall active enough that even as I approach goal weight I can create deficits via diet alone, without going too low on calories. I use strength training to reduce loss of lean mass and I use HIIT for cardiovascular fitness, but my calorie deficit comes from the kitchen.0 -
Now, on to my derailment...
Does recent diet have any impact on this conversation? i.e. training fasted vs fed? Or is the idea of fasted training somewhat of a misnomer?
Example, are "depleted glycogen stores" more likely to happen more quickly when training 16 hours after your last meal as compared to 3 hours? Lets assume fairly high intensity cardio for 60-90 minutes.
Anecdotal experience suggests it is so, but some of that may be mental.robertw486 wrote: »
This is one I've looked for some info on, and would welcome from those that have a more in depth understanding than I do.
From my basic knowledge, assuming that glycogen stores were properly replenished before any activity as mentioned above, the fasting really shouldn't matter unless it was for example fasting in combination with a high calorie deficit going on. In a normal maintenance state, the glycogen should be restored and available for use.
This might mean depleting glycogen stores quicker if you work out after extended fasts, as the carb and fat fuels are not as readily available, thus the glycogen would be used at a quicker rate to attempt to keep up with the intensity of the workout.
"assuming that glycogen stores were properly replenished before any activity "... "the fasting really shouldn't matter"
How did you mean to replentish glycogen stores while fasting?
Did you intend to say that while fasting, the body will break down fat stores into fatty acids and then use glyconeogenesis to reform those fatty acids into glucose and then glycogen? Because that can't happen in a fasted state. The harmones that are released during a fast will prevent gluconeogenesis from happening. So you have to break the fast in order to replentish glycogen stores.
Beacuse of the way you started this, the rest of what you are trying to say doesn't make much sense to me.
"training fasted vs fed?"
A “fasted” state means a person has not consumed any food before an exercise session, while a “fed” state means a person has had some form of fuel like carbohydrates, protein or fat ingested before hammering out a workout.
"Or is the idea of fasted training somewhat of a misnomer?"
No, you can actually workout without having eaten anything within the last few hours. You can sleep for 8 hours, wake up and eat nothing and run for an hour. I do this all the time. It happens quite a lot.
Example, are "depleted glycogen stores" more likely to happen more quickly when training 16 hours after your last meal as compared to 3 hours? Lets assume fairly high intensity cardio for 60-90 minutes.
So you sleep for 8 hours. Wake up and not eat. Your liver glycogen stores are pretty much depleted. Starve for another 8 hours and go for a workout? I never done this. But there were times I ate like crap then went for a run and it was the most horrible feeling in the world. Not exactly a 16 hour fast but the closest I have been to this.
Now what is really going on if you did attempt to do this. For the next 8 hours you are up. it depends what exactly are you doing for those next 8 hours? Laying in bed? Did you get up and walk to the couch and turn on the tv? Did you actually get up, take a shower, put some clothes on, walk to your car, go to work....
So a whole bunch of chemical actions are going on. many I am still learning about. To fuel your bodies needs for the next 8 hours, a combination of muscle glycogen, more fatty acids, and manybe even some protein break down is going to happen. Your brain is going to need a constant flow of glucose. Very little if any is left from the liver. So now the body has to get real creative in doing that. As long as you are not overworking the Krebs and ETC going on in ALL of your cells, you will use a lot of fatty acids, and your body may even break down some mucle tissue for the amino acids to make up any difference. If you do something anaerobic in nature, like start running 8 hours later, now you are forcing muscle glycogen to be used. Muscle glycogen can only be used by the nearby muscle cells. Only liver glycogen can be used universally. So your brain cannot tap into the glycogen that is stored in your thigh.
So by now the body has already released catabolic harmones which trigger the body to break down things like fat in the andipose and the muscle protein into amino acids. While the body continues to release these catabolic harmones, it prevents the body from releasing any anabolic harmones, like the ones that trigger the building and replentishing of glycogen. The same catabolic harmones is what makes you very hungry.
When glucose becomes very servely limited (which the brain needs), the body begins to manufacture ketone bodies from amino acids (and I am not sure if fatty acids or glycerol can be used) so the brain can continue running. Ketones, lactate, and glucose are the only 3 things that I am aware of that the brain can use.
So if you fasted for 16 hours, what you are realy saying by "depleating glycogen stores" is the muscle glycogen. There is nothing else available by now.
At low intensities, the muscles can use fatty acids at a much greater ratio. The higher intensity you go, you are basically forcing the muscle to use the local glycogen. And after fasting for 16 hours, even your local muscle glycogen store is not at full capacity. So yes, now you are even in bigger trouble.
"Lets assume fairly high intensity cardio for 60-90 minutes."
Believe me, you are not doing anything fairly high intensity for a 60 minutes. You will be able to sustain non-aerobic activity for as long as you got muscle glycogen left which isn't very much. You will begin to notice bonking effects rather quickly.
Now lets go a little bit less extreme. Sleep for 8 hours, wake up and go for a nice slow jog for 90 minutes at around 60% of your maximum heart rate. This is an intensity that will not force glucose use (but the body could prefer it if it wanted to).
Now in order to break down the stored fat into the fatty acids your muscle needs for making ATP, the body will need to release some harmones that encourage that. If you are in the habbit of eating mostly carbs whenever your body demanded it (i.e. you get hungry eat a cupcake within 5 minutes, you get hungry eat a bannana within 5 minutes, you get hungry you eat a sandwhich within a few minutes) then your body has gotten use to this. It lost some of the practice in using that stored fat, even if you are not obese. The process of breaking down your fat (triglycerides) into usable pieces (glycerol and fatty acids) is known as Lipolysis. The body releases lipase (an enzyme that catalyzes the hydrolysis of fats) in order to trigger lipolysis. When out of practice, the body is not very efficient in this area.
But by doing this 90 minute run every Saturday morning after fasting from the nigh before, during the week your body will get smart and produce even more liapase and other harmones that makes fat burning more efficient. So 4 weeks later, the same fasted 90 minute run will become easier. Why? The body has become more efficient in this process and has learned to predict that it will need to rely much more on fat for fuel.
Can you do this without fasting? yes you can. But to get the same effect you may have to run a little longer than 90 minutes or it may take you more than 4 weeks to notice a major difference in your Saturday morning runs.
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Commander_Keen wrote: »rankinsect wrote: »Commander_Keen wrote: »rankinsect wrote: »
actual way to burn the most fat is to burn the most total calories, regardless of where the calories come from, because in the long term the source of the energy is irrelevant.
With this quote in mind can you explain why people prefer HITT over running?
and lets be honest for every article that I see that HITT is better for weight loss, I see the same number of articles that say running for long periods of day is better for weight loss.
Well, I do HIIT, but I don't do it for fat loss, I do it for cardiovascular fitness. My reason for doing that over steady-state cardio: when I researched it, HIIT was the most time-efficient way to get good results (again, the results I want are fitness, not calorie burns). I wanted a workout with a time commitment I was willing to make for the rest of my life, and HIIT fit that need.
So you would not use HIIT for weight loss?
Some people may not be interested in weight loss or no longer interested in weight loss at all.
But are still concerned about fat burning capabilities for other reasons like the ability to run a marathon faster (which is the boat I am in).
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robertw486 wrote: »rankinsect wrote: »Commander_Keen wrote: »rankinsect wrote: »
actual way to burn the most fat is to burn the most total calories, regardless of where the calories come from, because in the long term the source of the energy is irrelevant.
With this quote in mind can you explain why people prefer HITT over running?
and lets be honest for every article that I see that HITT is better for weight loss, I see the same number of articles that say running for long periods of day is better for weight loss.
Well, I do HIIT, but I don't do it for fat loss, I do it for cardiovascular fitness. My reason for doing that over steady-state cardio: when I researched it, HIIT was the most time-efficient way to get good results (again, the results I want are fitness, not calorie burns). I wanted a workout with a time commitment I was willing to make for the rest of my life, and HIIT fit that need.
This is also something I've been looking into as far as the relationships of building glycogen store capacity to improve in other aspects of workout. As an example @arditarose does primarily weight training. Could HIIT type work help improve glycogen stores in specific areas, and possibly improve her weight training ability due to improvements in that area? I would think so, as any heavy lifting is influenced by both muscle and fuel. But it's still grey area to me due to less research into the matter.
You pretty much have a set limit on glycogen storage. (i.e. You parents gave you a shopping cart when they created you). Your job is to keep it full.
Now you can temporarily store over your stored limit by doing something called "carbo loading", but the effect doesn't last long. Usually you carbo load for 3 days leading into a mjor event. Like I will carbo load starting Wednesday, Thursday, and Friday for my Saturday morning marathon which I only do once a year. (maybe later I will do more marathons in a year but right now I am more interested in making sure I get enough training to improve before I do my next one).
So I don't regularly carbo load. I just do it just before the major event where i will need it.
For most normal activity you don't need to carbo load. You have enough stored glycogen (as long as you eat to keep it full). So what kind of activity are you trying to be better at where you need all this glycogen? I will almost guarentee that lack of glycogen storage is not going to be your delimiting factor.
So let's assume you wake up, have a nice breakfast and wait 3 hours for your liver and muscle glycogen stores to refill back up. Now you go on a run. A very hard run. Sprinting. You will eventually stop. A rookie runner will stop maybe in 2 or 3 minutes. An elite runner? Maybe 5 maybe 10 minutes depending how much of a sprint we are talking about. Now why did either of these runners stop running? Did they run out of glycogen? Nope! They ran out of oxygen. They ran so hard that now their anaerobic system is working much faster than their aerobic system. So within 3 minutes they reached their VO2 max and quickly die after that. They accumulated so much lactate and hyrdogen ions in their muscle that the muscle became so acidic that the brain basically shut those muscle cells down. They still have plenty of glycogen left. Lots of it in both the muscles and the liver.
Let's go a bit less extreme. They don't run at the VO2 max. They instead are running at their lactate threshold. How long can you run at this level? An hour tops. Maybe 50 minutes for a lesser trained athlete. Maybe 40 minutes for a very untrained athlete. Why did they stop? Same reason. It just took longer for the lactate and H+ to build up. Do they still have any glycogen left? Yes they do. Plenty of it.0 -
40 minutes? LTHR test is normally @ 30 minutes but first ten minutes is to get into the groove. 20 minutes FTP in cycling is what most do, 30 minutes to get closer to the mark, and 40km TT the gold standard.
I hope they get a production power meter for running soon as it has dramatically changed how cyclist train for the better.
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40 minutes? LTHR test is normally @ 30 minutes but first ten minutes is to get into the groove. 20 minutes FTP in cycling is what most do, 30 minutes to get closer to the mark, and 40km TT the gold standard.
I hope they get a production power meter for running soon as it has dramatically changed how cyclist train for the better.
Yes, 40 minutes. I was referring to someone running in an actual race. That's a worse case scenario.
Elites can actually race at their vLT for an hour. Now would you run a training run this way? No way.
Normal tempo workouts at vLT are maybe 20-30 minutes long.
I am not a cyclist so some of the terminology you introduced is new to me. Thanks for the post. I do appreciate the insight from your prospective.
Your post led me to DC Rainmaker and his primer:
http://www.dcrainmaker.com/2009/08/power-primer-cycling-with-power-101.html
So interesting topic of discussion here. Sorry for derailing the OP even further.
Yeah, we have no equivelent in the running world. I guess the closest thing we got is Dr. Jack Daniel's VDOT system to measure our capability in comparison to another runner?
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Hee. My sprints are usually 30 seconds and then a few minutes of walking (all with my fast dog) and then repeat
I don't like running. I do like sprinting! But it wears a body out. I couldn't do Tabata yet.
I do HIIT or whatever my version would be called to challenge my heart and bones, although it turns out it really helps insulin sensitivity overall (after a while) in a short exercise session. So time is a factor.
Also, though, I get repetitive stress injuries like crazy because I have EDS (connective tissue issues). Long running or even long walking will get me eventually every time, even with all the taping and splints and other silly-looking stuff. For some reason, i haven't gotten hurt yet sprinting (except DOMS
)! That's a win. I think it's just short enough to not bother my connective tissue the same way steady-state things do.
Nothing to do with weight loss for me
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40 minutes? LTHR test is normally @ 30 minutes but first ten minutes is to get into the groove. 20 minutes FTP in cycling is what most do, 30 minutes to get closer to the mark, and 40km TT the gold standard.
I hope they get a production power meter for running soon as it has dramatically changed how cyclist train for the better.
Yes, 40 minutes. I was referring to someone running in an actual race. That's a worse case scenario.
Elites can actually race at their vLT for an hour. Now would you run a training run this way? No way.
Normal tempo workouts at vLT are maybe 20-30 minutes long.
I am not a cyclist so some of the terminology you introduced is new to me. Thanks for the post. I do appreciate the insight from your prospective.
Your post led me to DC Rainmaker and his primer:
http://www.dcrainmaker.com/2009/08/power-primer-cycling-with-power-101.html
So interesting topic of discussion here. Sorry for derailing the OP even further.
Yeah, we have no equivelent in the running world. I guess the closest thing we got is Dr. Jack Daniel's VDOT system to measure our capability in comparison to another runner?40 minutes? LTHR test is normally @ 30 minutes but first ten minutes is to get into the groove. 20 minutes FTP in cycling is what most do, 30 minutes to get closer to the mark, and 40km TT the gold standard.
I hope they get a production power meter for running soon as it has dramatically changed how cyclist train for the better.
Not sure where some of this is coming from but I have a guess. The FTP "gold standard" is 60 minutes. Most people can not concentrate for a full 60 minutes so 20 minutes was used and 95% (or 92.5% depending on who you talk to) of your avg power during that 20 minute effort became your FTP.
I think the myth of the 40K ITT being used for FTP values comes from many people take about 60 minutes to complete, however most elite athletes will be well under 60 minutes depending on course.
Of course all this is transient as with training the numbers will change and another test needed to set the new baseline.
Running - it's always been time and distance...no PM needed. Same as on a velodrome, unless you are doing standing start power events, time and distance will get all the adaptations needed for improvements. Don't make this any more complicated than necessary.
Back to eating popcorn and enjoying the exchange of all this science. Great reading.0 -
It's a luxury as much as a HRM and a GPS watch. Unlike other metrics, a PM measure your work independent of other factors such as it's too cold, a bad night's sleep, dehydration, bad head wind, steeper climb, etc. It allows one to evaluate one's training effort subjectively, train in a more structured manner, and is a great pacing tool.
Yes one can do without and win big/reach your goals. But ask yourself does that expensive pair of shoes or moisture wicking top necessary? It's a tool.
Opinions are mostly split with regards to recreational cyclists but not pros or amateur racers. The biggest barrier is price (and to some extend adhering to structural training and learning how to interpret the data). But than I see the same folks spending 500+ on a new set of wheels and more for another bike, and often train by HRM. The bang for the buck is night and day with a PM verses a lighter bike. It's the engine first.0 -
robertw486 wrote: »@rankinsect
Great post, well reasoned, and in line with what your norm is. Great timing for me personally too, as this is something I've been working on expanding my knowledge of.ericGold15 wrote: »
Or not. From 'MedFitness, associated with the U of Michigan:.Glycogen isn't used first - the vast majority of exercise is fuelled from a blend of fat and glycogen (carbohydrate) in differing proportions. During lower intensity exercise fat is the predominant fuel, higher intensity carbohydrate is the predominant source. If I remember correctly the 50/50 point is roughly 70% of max HR but sure someone can correct me.Exercising for longer than 30 minutes shifts the primary macromolecules that are metabolized from glucose to fatty acids. Shifting from glucose and glycogen supplies allows the body to efficiently mobilize and utilize free fatty acids (FFAs) derived from lipids in adipose tissue, which resides mainly under the skin.
... ...
After the first 30 minutes of exercise, the body runs out of its glycogen storage and then turns mainly to what is left of the glucose in the blood and then finally to fat and amino acids derived from muscle protein. Supporting evidence of fatty acid release comes from physiologic research where human gluteal fat cells isolated after 30 minutes of biking showed that cathecholamine induced lipolysis had increased between 35-50% 4. If exercise does not last until 30 minutes then fat burning is never achieved because all of the glycogen is not used u p. So while one may be able to prevent adding fat to the body, one is not metabolizing fat from the adipose tissues during the exercise. In short, exercises aerobically for less than 30 minutes, one is just maintaining the adipose tissue status quo and decreasing muscle mass.
A little Googling found numbers that you mention, based on a 1994 study of endurance athletes studied after an overnight fast.
Thanks for the giggles - that article is hilarious!
Running out of glycogen storage after 30 minutes - really?
Think of the burn rate needed to run through approximately 500 grams of carbohydrate in 30 minutes and you will see what nonsense that is.
Think of how far runners can go before they "hit the wall" or how long a cyclist goes before they "bonk". And how awful it feels (crushing and sudden fatigue, mental confusion such as forgetting to put your feet down when you stop pedalling! Yep done that.).
During a 20 minute VO2 max test I went from RER of 0.82 during the gentle start (0.7 is totally fat fuelled) progressively through to RER of 1.0 (totally carb fuelled) after about 15 minutes building to very high intensity and eventually anaerobic at maximal effort / failure.EvgeniZyntx wrote: »ericGold15 wrote: »
Or not. From 'MedFitness, associated with the U of Michigan:.Glycogen isn't used first - the vast majority of exercise is fuelled from a blend of fat and glycogen (carbohydrate) in differing proportions. During lower intensity exercise fat is the predominant fuel, higher intensity carbohydrate is the predominant source. If I remember correctly the 50/50 point is roughly 70% of max HR but sure someone can correct me.Exercising for longer than 30 minutes shifts the primary macromolecules that are metabolized from glucose to fatty acids. Shifting from glucose and glycogen supplies allows the body to efficiently mobilize and utilize free fatty acids (FFAs) derived from lipids in adipose tissue, which resides mainly under the skin.
... ...
After the first 30 minutes of exercise, the body runs out of its glycogen storage and then turns mainly to what is left of the glucose in the blood and then finally to fat and amino acids derived from muscle protein. Supporting evidence of fatty acid release comes from physiologic research where human gluteal fat cells isolated after 30 minutes of biking showed that cathecholamine induced lipolysis had increased between 35-50% 4. If exercise does not last until 30 minutes then fat burning is never achieved because all of the glycogen is not used u p. So while one may be able to prevent adding fat to the body, one is not metabolizing fat from the adipose tissues during the exercise. In short, exercises aerobically for less than 30 minutes, one is just maintaining the adipose tissue status quo and decreasing muscle mass.
A little Googling found numbers that you mention, based on a 1994 study of endurance athletes studied after an overnight fast.
Thanks for the giggles - that article is hilarious!
Running out of glycogen storage after 30 minutes - really?
Think of the burn rate needed to run through approximately 500 grams of carbohydrate in 30 minutes and you will see what nonsense that is.
Think of how far runners can go before they "hit the wall" or how long a cyclist goes before they "bonk". And how awful it feels (crushing and sudden fatigue, mental confusion such as forgetting to put your feet down when you stop pedalling! Yep done that.).
During a 20 minute VO2 max test I went from RER of 0.82 during the gentle start (0.7 is totally fat fuelled) progressively through to RER of 1.0 (totally carb fuelled) after about 15 minutes building to very high intensity and eventually anaerobic at maximal effort / failure.
Agreed, it's ridiculous to talk about "running out of glycogen" without mentioning intensity. Light exercise is basically glycogen neutral. High intensity work (RER 1, preferentially CHO fuelled) will reduce global stores to about 20% in one hr in the trained athlete.
What does the bolded above actually mean? Exercising for less than 30 minutes now suddenly decreases muscle mass?ericGold15 wrote: »In short, exercises aerobically for less than 30 minutes, one is just maintaining the adipose tissue status quo and decreasing muscle mass.
First off, great post @rankinsect
Now, on to my derailment...
Does recent diet have any impact on this conversation? i.e. training fasted vs fed? Or is the idea of fasted training somewhat of a misnomer?
Example, are "depleted glycogen stores" more likely to happen more quickly when training 16 hours after your last meal as compared to 3 hours? Lets assume fairly high intensity cardio for 60-90 minutes.
Anecdotal experience suggests it is so, but some of that may be mental.
This is one I've looked for some info on, and would welcome from those that have a more in depth understanding than I do.
From my basic knowledge, assuming that glycogen stores were properly replenished before any activity as mentioned above, the fasting really shouldn't matter unless it was for example fasting in combination with a high calorie deficit going on. In a normal maintenance state, the glycogen should be restored and available for use.
This might mean depleting glycogen stores quicker if you work out after extended fasts, as the carb and fat fuels are not as readily available, thus the glycogen would be used at a quicker rate to attempt to keep up with the intensity of the workout.Commander_Keen wrote: »rankinsect wrote: »
actual way to burn the most fat is to burn the most total calories, regardless of where the calories come from, because in the long term the source of the energy is irrelevant.
With this quote in mind can you explain why people prefer HITT over running?
and lets be honest for every article that I see that HITT is better for weight loss, I see the same number of articles that say running for long periods of day is better for weight loss.
Because you need more articles to convince people to buy HIIT videos or buy HIIT plans. Running long periods? Well there are books and training plans that will get a newbie runner to running a marathon in only 18 weeks (which I disagree with btw). And you want to do that because look at all the weight you could lose training for that marathon (not to mention the expensive shoes you will need to buy every 3 months).
A more realistic answer: Time. People either have busy schedules or low interest to spend more time for exercising. If I told you that you could burn 200 calories in 20 minutes or 500 calories in an hour? Which one would you pick? Many people would pick the 20 minute workout. That is what HIIT gives you. More bang for those 20 minutes. But if you slow it down and go longer, you could burn even more calories. So there is truth to be told from both point of views. How you present the information to the reader depends on if you are selling a HIIT video or convincing someone that you need to train for a marathon or half marathon.
I would think that even at a level that will call on glycogen stores, a steady state workout at max capacity for the time frame involved would still trump any actual HIIT for calorie burn. Real high intensity would rely on glycogen, but the cardio overload is quick. Even if workload was maintained the aerobic zone, the upper edge of the aerobic zone would trump in calorie burn IMO.
From a scientific point of view, what exactly does this mean? What exactly triggers a particular muscle cell to pick glucose for energy instead of fat or vice versa?
I know if you are in oxygen debt, meaning the mitochondria doesn't have enough oxygen to support Krebs Cycle and ETC, then the muscle cell will need to burn a carb using glycolysis to meet that particular demand for ATP.
But what if oxygen was available? What triggers a specific muscle cell to prefer a fatty acid instead of glucose when both (glucose and fatty acid) are avaialable to the muscle cell?
So when you say a level that will call on glycogen stores, I intepret this to mean any intensity that requires an energy demand that exceeds what the aerobic system can support. So harder than a slow easy run but less intense than what exactly? Steady state workout a max capacity? Maximum what? Vo2Max? max heart rate?
I am not an expert on HIIT but aren't you sort of hitting the maximum capacity for that muscle group for a certain time frame? Even if the time frame was say 20 seconds? Then you move onto another muscle group and work that muscle group for maximum capacity for say another 20 seconds? Then quickly move to another muscle group that is rested and repeat. The sum of all the working of all the different muscle groups without stopping is a form of steady state from the heart's point of view.
So I am just confused as to what you are trying to express. Maybe a more detailed explanation would help?
"Real high intensity would rely on glycogen, but the cardio overload is quick. Even if workload was maintained the aerobic zone, the upper edge of the aerobic zone would trump in calorie burn IMO."
This sentence is conflicting. real high intensity which would rely on glycogen (meaning you have to force the anaerobic system to work harder than the aerobic system)... Even if workload was maintained the aerobic zone. See the oxymoron here? How can you force an intensity out of the aerobic zone but maintain the aerobic zone?
Look up glycolysis, krebs cycle, and electron transport chain.
Unless you are burning fatty acid or amino acid, the use of glycogen in the Krebs Cycle has to start with glycolysis. It's not like glucose can be used and circumvent the anaerobic system of glycolysis. So if you are forcing intensity to use glycogen, I don't know how else that could happen unless you go beyond your aerobic zone. The only way I know to avoid the anaerobic zone is running an intensity that could use fatty acids.
Unless I am missing something here?
@Stoshew71 The multi quote here is a pain, but I'll try to address all the questions posed. Keep in mind that I'm looking for more specific answers than I have and not attempting to claim any expertise in this area.
Per HIIT and glycogen use vs fats. Properly used, glycogen stores can allow overload beyond VO2 max for a period of time. The use of carbs vs fats as I understand it varies somewhat, starting as low as 50-60% of VO2max for some, while being quite high (possibly 80-85% VO2max) for others. Though there are tests that indicate a strong cardio base might have influence on when and how quick the transition takes place, they don't seem to be showing a strong trend of what has the greatest influence.
So I'm stating that crazy hard HIIT, though high in calorie burn per minute, involves loads so high that you can't maintain them for anything other than a brief period. From my understanding of glycogen use above, I would think that for any person sustained maximum output would always trump in calorie burn, unless the time period was very short. It would use both carbs and fats for fuel most likely. As an example I did what I calculated to be a true Tabata IE1 protocol HIIT on my elliptical. In less than 2 minutes of the actual loaded time at 170% of VO2max, I burned just over 60 calories. (I actually slightly exceeded 170%). But during my 10 minute warm up (which I screwed up and did slightly high based on the actual protocol) I burned over 100 calories, with much less physical effort. Based on my current cardio health, I would estimate that in a 10 minute time frame I could knock out above my estimated VO2max without issue. As an example, I often do a more extended but lower load interval or three at the end of my cardio, and can sustain say a load of 120-130% of VO2max for minutes, rather than seconds, at a time. It's a downward slope but HR is much more in control as is breathing effort.
As for when my glycogen stores transition into the picture, I wish I had more answers. I know that I've only actually "bonked" a couple times in my life, under very high load long term conditions. And I also know that recovery from a "bonk" is fairly quick, and hours later with some fuel a person can once again exert beyond cardio zone fat burning levels. But much like you, I'm interested in the specifics of how quick one can restore glycogen levels, how to use them only when needed better, etc.0 -
robertw486 wrote: »
@Stoshew71 The multi quote here is a pain, but I'll try to address all the questions posed. Keep in mind that I'm looking for more specific answers than I have and not attempting to claim any expertise in this area.
Per HIIT and glycogen use vs fats. Properly used, glycogen stores can allow overload beyond VO2 max for a period of time. The use of carbs vs fats as I understand it varies somewhat, starting as low as 50-60% of VO2max for some, while being quite high (possibly 80-85% VO2max) for others. Though there are tests that indicate a strong cardio base might have influence on when and how quick the transition takes place, they don't seem to be showing a strong trend of what has the greatest influence.
So I'm stating that crazy hard HIIT, though high in calorie burn per minute, involves loads so high that you can't maintain them for anything other than a brief period. From my understanding of glycogen use above, I would think that for any person sustained maximum output would always trump in calorie burn, unless the time period was very short. It would use both carbs and fats for fuel most likely. As an example I did what I calculated to be a true Tabata IE1 protocol HIIT on my elliptical. In less than 2 minutes of the actual loaded time at 170% of VO2max, I burned just over 60 calories. (I actually slightly exceeded 170%). But during my 10 minute warm up (which I screwed up and did slightly high based on the actual protocol) I burned over 100 calories, with much less physical effort. Based on my current cardio health, I would estimate that in a 10 minute time frame I could knock out above my estimated VO2max without issue. As an example, I often do a more extended but lower load interval or three at the end of my cardio, and can sustain say a load of 120-130% of VO2max for minutes, rather than seconds, at a time. It's a downward slope but HR is much more in control as is breathing effort.
As for when my glycogen stores transition into the picture, I wish I had more answers. I know that I've only actually "bonked" a couple times in my life, under very high load long term conditions. And I also know that recovery from a "bonk" is fairly quick, and hours later with some fuel a person can once again exert beyond cardio zone fat burning levels. But much like you, I'm interested in the specifics of how quick one can restore glycogen levels, how to use them only when needed better, etc.
@robertw486 Please allow me to retort paragraph by paragraph....
"The multi quote here is a pain, but I'll try to address all the questions posed. Keep in mind that I'm looking for more specific answers than I have and not attempting to claim any expertise in this area."
hahaha I am a very curious student as yourself. :-)
"Per HIIT and glycogen use vs fats. Properly used, glycogen stores can allow overload beyond VO2 max for a period of time. The use of carbs vs fats as I understand it varies somewhat, starting as low as 50-60% of VO2max for some, while being quite high (possibly 80-85% VO2max) for others. Though there are tests that indicate a strong cardio base might have influence on when and how quick the transition takes place, they don't seem to be showing a strong trend of what has the greatest influence."
Yes, that is my understanding as well. In fact, the transition (or I would describe it more as a meter shifting from low concentrations of glucose use and high concentrations of fat use - to high concentrations of glucose use and low concentrations of fat use since you don't really shift immediately from 100% use of one direction to 100% in the other). How exactly you control that dial is one of the Holy Grails. I think lots of continued research is still going on in this area as there is still great debate. I just know that the more intense your exercise (closer and beyond VO2max) the more glucose burn needed since you are breaking oxygen debt.
In fact, lactate threshold is the magic zone that I usually go by. To the left of LT: both fat and glucose are used at some mysterious ratio that I am more curious to learn on how that works. But as you approach LT, glucose is being used more and more since oxygen debt increases. At LT, lactate accumulation steady states which means some anaerobic activity has reached some equilibrium compared to the buffering and clearing of this lactate. Lactate is a result of anaerobic activity outpacing (or overloading as I think you are describing) the aerobic system. But since the body is very good at buffering and clearing this lactate, it becomes a wash for a while. Thus LT is the sweet spot. One can at best maintain LT intensity for about an hour (a little less for less trained individuals). So anything to the right of LT means anaerobic output is not only greater than aerobic input, but even greater than the body's capability to counter the negative lowering of pH caused by the H+ ions. So while exact intensity at LT is about an hour, go just a little to the right and things start to break down exponentially.
I just ran a marathon (26.2 miles) in 3:38:00. According to McMillan, my pace for LT is 7:37 min/mile and my pace for VO2 max is 6:35. I am not sure how that works but I should be able to run a min/mile faster in order to reach VO2max. I should be able to run for about an hour at LT but can only run less than 10 minutes at VO2max. If that best explain the correlation between LT effect and VO2max effect.
V02 max is defined as the maximal volume of oxygen that the body can deliver to the working muscles and the maximum efficiency the muscles will use that oxygen. So while we move past LT, we are still making more use of oxygen until we reach VO2max, but we are producing lactate at a greater rate (meaning more reliance on anaerobic output thus greater use of glucose than fat). But the penalty is that the body can no longer control the negative effects of lactate and H+ ions.
I don't have any data to back this up, but I would guess that glucose reliance is greater than 50% before we even reach LT. But that would just be my guess from my limited understanding.
RQ definitions: My understanding that if you had 100% glucose respiration, you would have an RQ of 1.0, and 100% of fatty acids yields an RQ of 0.71. The average RQ during mild to moderate exercise before LT is approximately 0.85. Beyond LT and we start to go beyond 1.0. The rise beyond 1.0 thus signifies greater use of glucose, but more importantly that output volume of CO2 is outpacing the input volume of O2. I am not sure exactly what this means. LOL
To bring this to an end, why HIIT can only be done in short intervals is due to the body's inability to no longer buffer and clear the negative effects of the hydrogen ions (H+) produced during anaerobic fermentation during glycolysis. HR in comparison to LT and VO2max are highly individualized. But LTHR is somewhere between 75-85% of your HRmax. If you exert an intensity between 95-100% of max HR, you will reach VO2max within 4 minutes. According to some data I found.
"So I'm stating that crazy hard HIIT, though high in calorie burn per minute, involves loads so high that you can't maintain them for anything other than a brief period. "
This seems to sum up what I wrote above very well.
For this reason, many more folks use LT as a major training zone as opposed to VO2max.
"In less than 2 minutes of the actual loaded time at 170% of VO2max, I burned just over 60 calories."
I am curious, exactly how did you measure your 170% of VO2max and how did you measure going beyond 100% of VO2max?
I have been for the last 6 months concentrating on marathon training so I haven't done any VO2max workouts. I also don't wear my HR monitor much. I do want to do more VO2max workouts this upcoming year to increase my raw speed. So I have no personal data on VO2max. Most of my training has been centered around LT and pacing and timing at specific paces at or below LT.
"As for when my glycogen stores transition into the picture, I wish I had more answers. I know that I've only actually "bonked" a couple times in my life, under very high load long term conditions."
I only bonked once. Last year's marathon. I was able to maintain around an 8 min/mi pace for about 15 miles then around 8:30 for the next 2 miles then the min per miles got really bad after that. I bonked around mile 22 and was forced t into walking more than running for a few more miles after that. I attributed my bonking to targeting too high of an intensity from the start and poor refueling during the marathon. I also didn't do very well with even pacing. I had finished at 3:50:16.
I attributed lactate threshold workouts, better even pacing, and better refueling/hydration (constant intake of Gatorade that I carried with me) and a better understanding of what target pace to shoot for. This allowed me to knock down over 12 minutes from my marathon time in just a year.
I have absolutely no RQ data so I don't know fat/glucose percentages on any of my runs, but I know I am better utilizing fat metabolization now than I was a year ago. Offcourse this is all related to performance and endurance since I am no longer trying to lose weight.
"And I also know that recovery from a "bonk" is fairly quick, and hours later with some fuel a person can once again exert beyond cardio zone fat burning levels. But much like you, I'm interested in the specifics of how quick one can restore glycogen levels, how to use them only when needed better, etc."
My experience is that hi-glycemic carbs is very immediate. My bonk experience last year. At around mile 22 I could only walk and couldn't run at all. I reached an aide station where I took in 2 Dixie cups of PowerAde. Within 10 minutes I was able to run again to finish my very last mile running at a very slow pace. 9:36 to be exact compared to 10:32 and 10:55 for my previous 2 miles.
During my training and recovery after long runs, the quicker I can get some nutrition in, the better I will recover.0 -
Endurance training is my silver bullet.
I won't put up the map my ride screen shot cuz they are freakin huge...
But this morning was 40 mile ride, then 10K run. 8 minute transition into run gear from cycling clothes.
The long steady state workout blasted out 7 pounds of water and glycogen.
There is a bit more fat burned in the. Ox since I do this every weekend and my body is a bit more adapted to burn a higher fat mix.
But... A few intervals at 95% HRM in the run make it great to smoke out blood glucose. The bike ride was all in Z2. So when it is over the benefits are raising my lactate threshold and getting more fat adapted after burning out the glycogen
There is a second half to the burning off glycogen equation. The fat adapted side. I push my body to burn a higher mix of fat by doing fasted Z2 cardio for 2-4 hours. It is my personal silver bullet for stripping off body fat. Your mileage may vary.
Anyway. Great discussion. It was nice to read up on a few things I have never heard of.
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BTW, I did get my A1C retested right after I posted in this thread. To my shock, it actually increased despite the substantial increase in low to moderate exercise I had been doing since early October. However, I did increase my carb consumption with my increased exercise, so (despite no increase in body fat) unfortunately I think I managed to nullify most of the effects from exercise. Seems like the only solution at this point for me is to decrease carbs, since 60+ minutes of at least low end moderate exercise a day is not enough. I had also mixed some more vigorous exercise in as well during this time.0
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