A Couple Of "Bonk" Questions
 

Let's assume that you went out on a long ride without enough fuel before/on the ride and you bonk bigtime.

If after the ride you stayed on a SUPER low carb (say less than 10 grams per day) diet, I assume that through some process of digesting fat and protein that your glycogen stores would eventually be replenished. Is that correct and how much 'extra time' would it take (plenty of post ride calories but just no carbs).

Is there any value in incorporating bonks into your training? I was wondering if training in a state of glycogen depletion might improve the rate at which your body can convert fat to glucose.

Thanks.

dave

No, there is no value.

During bonking gluconeogenesis will convert liver stores of polysaccharides into glucose in an effort to increase or stabilize your blood sugar, thus allowing the pancreas to provide insulin. Without insulin, your body can't uptake amino acids to build and/or repair muscles. When the liver is near exhausted this glucagon converts any free amino acids into glucose , then it goes after muscle mass converting protein into glucose. Your brain needs something like 120 or 150 grams of glucose and the body will be in a crises mode trying to provide it. Replenishing muscles with glycogen is the last thing your body is concerned with. If starvation continues ketones can be used as fuel by the brain but at this point, you are losing muscle mass and your body is in a survival mode. Not exactly the type recipe an athlete needs. Its never good to lose muscle mass, or stress your system to its limits.

Not to mention that it is agony trying to ride while bonking. All you want to do is stop. You won't want to ride much if your training puts you in that state with any degree of regularity.

The one time I bonked real hard, I didn't just want to stop, I wanted to die, too. I shifted into the lowest gear I had, and I still couldn't get my cadence meter above 80 on flat ground. It's not fun. It's very dangerous. In short, don't do it.

I bonked once last year and it wasn't fun. Not sure if it was not enough food, not enough water, or both. But I, too, found myself in the lowest gear, barely able to pedal, also on flat ground. Also humiliating because it happened on a club ride.

Thanks for the info/perspective. I still have the question "can you replace your glycogen stores on a virtually carb-free diet?"

dave

I have read studies that partial replacement is possible and that is consistent with my experience.

I have trained my body to burn fat and have spent months in nutritional ketosis and have intentionally bonked on training rides. I am nearly bonk-proof now, besides the brain prefers ketones.

Yes, it's called gluconeogenesis.

I used to have a routine for big races that didn't involve bonking, but did have me riding when very carbo depleted. Say I had a Cat 1,2,3 100 mile race on Sunday. A big race for this Cat 3 back in the '70s when there were just not enough long hard races. I'd ride 120_ miles the Sunday before. Carbo depletion. Monday and Tuesday were low carbo days, riding my usual 45 miles before breakfast. Not a whole lotta fun. Wednesday the same ride and normal diet. Thursday and Friday I tapered down the riding and ate LOTS of carbos. Fun! From Friday evening on, nothing but fruit, water and juice, as much as I wanted.

Race day, my body felt completely clean and fueled. Speed the first two hours was a little off, but if I could get past halfway, from there I just got stronger. I did this for my best race, a very fast 105 miles and hills. Wasted a lot of energy in a wasted break but still managed to make the cut at mile 90 and finish in the money and under the old course record.

Ben

mr_pedro, thanks for the follow-up.

dave

79p, what you described sounds EXACTLY like the typical protocol for what runners back in the 70's and 80's called 'carbohydrate loading' before running a marathon. I don't know if it is still 'popular' or not.

dave

"Gluconeogenesis is the metabolic process by which organisms produce sugars (namely glucose) for catabolic reactions from non-carbohydrate precursors"

Sure...if you are into masochism.:lol:

If that is the case then if there is a process by which just fats and/or protein can be converted to GLYCOGEN stores in your muscles and liver, it has not been discussed here (in a form that I can recognize, anyway).

Thanks.

dave

Gluconeogenesis is the synthesis of glucose (not glycogen) from noncarbohydrate sources, that is from fat and protein. Glucose produced during gluconeogenesis is used for your current glucose needs, so it is not stored as glycogen, at least not under low-carb diet conditions.

Your brain uses 400-500 Calories per day and can normally rely only on glucose as an energy source, so you need at least 100 grams of carbs for brain needs alone. When you consume less than 100 grams of carbs per day, your body will need to start produce an alternative source of energy for the brain - that is ketones.
http://www.nutrientsreview.com/carbs...s-glucose.html

So, you may eat even 100 grams of carbs per day but you will still not likely replenish your glycogen stores.

Yet another issue is that your leg muscles can use only glycogen from leg muscles, not from other muscles...

I can still remember the first (and last) time I bonked. It was not fun. I had to get off my bike and sit down on the ground. I was that bad. A friend of mine asked me what I ate for breakfast and I said "I don't remember". Not because my brain was foggy, but because I didn't want to admit to having ate next to nothing. Never did it again.

I was also interested in the gluconeogenesis - gycogen question, so I looked it up:
http://www.******.com/r/Fitness/comm...sis_replenish/

It took some looking. The biochem texts I found were impenetrable by li'l ol' me. So, no you can't make glycogen by means other than eating more carbs that your body needs for current activities. There's no other pathway.

And what should be of even more interest to the low-carb folks: gluconeogenesis only converts protein to glucose. Fat cannot be converted to glucose. Therefore your protein intake needs to be sufficient to handle your blood glucose needs or you'll burn muscle for it.

It works, but is no longer popular. Trainers have decided that the metabolic load imposed by the glycogen cycling was, in the long run, not worth the extra performance. But I think if you only did it a couple times a year that would be fine.

Getting back to the OP, there is research to suggest that low-gycogen training can be beneficial. This is not the same as bonking. Though one hears the term "bonk-training" bandied about it's mostly used in the context of going out fasted in the morning with only water, which can be beneficial for sure but has nothing to do with real bonking.

Sports nutrition: the latest research into low glycogen training
Science of Running: Evidence for Doubling, training in glycogen depleted state

@Carbonfiberboy, glucose can be synthesized from glycerol, which is a breakdown product of fat.
Mathews/van Holde/Ahern 3rd Edition

Sorry sir, but you're misinformed. Your source doesn't understand the bio-chem either.

According to you, we're going to wither away and die without carbs. In fact, carbs are the one macro we can live entirely without and they certainly are not required to fuel 'current activities'.....

"The brain cannot DIRECTLY use fat for energy. Once liver glycogen is depleted, without a backup energy source, humanity would’ve long disappeared in the eons of evolution.The backup is ketone bodies that the liver derives primarily from fatty acids in your diet or body fat. These ketones – β-hydroxybutyrate (BHB), acetoacetate and acetone – are released into the bloodstream, taken up by the brain and other organs, shuttled into the “energy factory” mitochondria and used up as fuel. "

There is a pecking order glucogen then ketones.... remember that even a way low bmi person still has 30 40 k calories of fat to convert to ketones.

"After several days of fasting, all cells in the body begin to break down protein. This releases amino acids into the bloodstream, which can be converted into glucose by the liver. Since much of our muscle mass is protein, this phenomenon is responsible for the wasting away of muscle mass seen in starvation."

Technically yes, but link to a study showing that this happens in humans . . .

Sure don't get where you're coming from. Who said anything about dying? But thank you for making my point more strongly. The last sentence in your post describes the muscle breakdown process when protein is not eaten, even though there is plenty of fat available in the body.

Fasting humans can convert glycerol to glucose.
Glycerol gluconeogenesis in fasting humans. - PubMed - NCBI

The other part of the triglyceride molecule --fatty acids-- are not or at least are not efficiently converted to glucose.
Glucose Can Be Synthesized from Noncarbohydrate Precursors - Biochemistry - NCBI Bookshelf

No, it doesn't make your point.... and no, you don't get it....and yes, it obvious that you have no intention of getting it.