You don’t have to WALK when you deplete your glycogen. A FAT ADAPTED ATHLETE can still run (albeit not as fast) on FAT when their glycogen is gone. It takes time and patience to become FAT ADAPTED. I’m such a runner. I start running 19 hrs into my fast and still run 10miles comfortably. 1 gram of carbs = 4 calories of energy. 1 gram of fat = 9 calories of energy.
Rob: Thanks for the good note. Good discussion. Actually, our subconscious brain keeps us from actually completely running out of glycogen. The "governor" kicks in, and shuts us down. So, in part, it does depend on your experience with running on low glycogen reserves. Many can continue running slow, even when glycogen depleted. Now, if you are talking about ketosis, and using ketones, which come from fat, instead of glycogen, in general, I find those people are typically slower overall. Highest intensities, for example, which someone is normally capable of, become impossible, on ketones alone. Yes, for all, fat is the more abundant resource for ATP (fuel). The average non-pro athlete, only has about 80 to 90 minutes of heart rate, higher than lactate threshold (a bit faster than Marathon Race Pace), before they hit the wall, or glycogen depleted. So we all use fat on the marathon. Hope this adds a bit to the discussion. Yes, we can train our bodies, with diet and low intensity exercise, to use more fat than normal. And speed work raises the bar on your ability to go faster. But without glycogen, as you suggest, we are a bit slower, which also depends on training.
Great video! Glad i found this about 2 weeks before LAM '24. Looking forward to this being my first marathon ever. And yes, i will start sloooooow.
You don’t have to WALK when you deplete your glycogen. A FAT ADAPTED ATHLETE can still run (albeit not as fast) on FAT when their glycogen is gone. It takes time and patience to become FAT ADAPTED. I’m such a runner. I start running 19 hrs into my fast and still run 10miles comfortably. 1 gram of carbs = 4 calories of energy. 1 gram of fat = 9 calories of energy.
What is your fat-adapted marathon PR? In other words, what's your fastest finish without taking in carbs during the race?
Rob: Thanks for the good note. Good discussion. Actually, our subconscious brain keeps us from actually completely running out of glycogen. The "governor" kicks in, and shuts us down. So, in part, it does depend on your experience with running on low glycogen reserves. Many can continue running slow, even when glycogen depleted. Now, if you are talking about ketosis, and using ketones, which come from fat, instead of glycogen, in general, I find those people are typically slower overall. Highest intensities, for example, which someone is normally capable of, become impossible, on ketones alone. Yes, for all, fat is the more abundant resource for ATP (fuel). The average non-pro athlete, only has about 80 to 90 minutes of heart rate, higher than lactate threshold (a bit faster than Marathon Race Pace), before they hit the wall, or glycogen depleted. So we all use fat on the marathon. Hope this adds a bit to the discussion. Yes, we can train our bodies, with diet and low intensity exercise, to use more fat than normal. And speed work raises the bar on your ability to go faster. But without glycogen, as you suggest, we are a bit slower, which also depends on training.
This guy burned a quarter of his glycogen stores just talking about mile 1. Geeesh...get on with it!!
If you are fat-adapted, you shouldn't need to worry about glycogen