Tim Egge retweetledi
Let me dump some carbs on you...
Someone said yesterday that thinking about CHO intake in terms of stores, output and "bonking" is the "old way" of looking at carbs in sport.
That pissed me off.
So, let's start with...
Only those with a bullet-proof basic understanding can have an advanced understanding.
Put another way, he couldn't tell me why this is the case. So, let me tell you why this is that case...
The error in thinking of a carbohydrate/glycogen "reservoir" comes largely in the sense that the reservoir isn't one tank.
We have...
Tank 1: Liver Glycogen
Tank 2-2,000,000 Muscle Glycogen
That is, every muscle fiber has its own little tank. So, in terms of glycogen depletion, while a significant drop in liver glycogen is obvious - the typical "bonk"...
Drops is muscle glycogen are far more subtle...
They manifest as progressive transition from more economical fibers to less economical. So, over the course of the race, pace for a given O2 uptake progressively decreases.
*Assuming CHO makes it across the gut wall to the blood*...
High levels of exogenous intake can offset this progressive depletion of more economical fibers & keep the pace high for a give O2 uptake over longer periods of time.
This is why, again, assuming good levels of clearance from the gut, high CHO intake can have a small, but meaningful impact on the pace that can be held late in a race.
TLDR...
- A liver glycogen bonk is obvious.
- Muscle glycogen depletion is subtle.
- Exogenous CHO can offset glycogen depletion (to an extent) & help to maintain pace for longer.
But....
1/ The size of the engine determines fuel needs.
2/ You can only use what you can clear (& if you can't clear it, there's a timebomb jostling around in your gut - just waiting to go off)
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