I reviewed your whole thread.
I experience the same thing, reliably, if I consume 60-90g/hr, and wait even 15 minutes post-ride to stuff my face with carbs. (My PhD is Sport Physiology, and I’m a mediocre very muscular cyclist, for context).
Here’s why it’s happening, assuming no pathology, which it sounds like you’re ruling out:
- Big sugar intake during ride.
- High exertion during ride.
- Rapid response of muscle tissue GLUT4 (and other stuff) to vacuum glucose out of bloodstream.
- Any lingering sugar in bloodstream further increases post-exercise insulin response (which, yes, is dampened by exercise but pancreas will still respond to appropriately elevated blood sugar).
- BOOM crash.
Your previous 15-30g per hour protocol essentially upregulated gluconeogenesis at the liver during exercise, due to you not fueling sufficiently. The “crash” happened during exercise but was blunted by the secretion of glucagon and epinphrine among other things, that are stimulated by actively exercising.
Now that you’re fueling with more carbs per hour, you’re not having quite as dramatically increased gluconeogenesis or glycogenolysis rates in liver, and so when you cease consumption of carbs at the end of the workout, your muscles don’t initially cease vacuuming the sugar up from the blood, meanwhile your liver is sitting there too-slowly upregulating glucose release because it’s like “nah, man, you’ve been hammering carbs, you got this.”
Hence: Crash.
How to fix:
- Consume even more during exercise. 100-140g is totally feasible. Review my recent activity throughout the forum for more info.
- Consume carbs right after training. Don’t wait.
- DEFINITELY don’t cut off consumption 30min prior to ceasing ride. Consume right up to the end of the ride and immediately after. (Like, keep drinking your carb bottle, as you get changed, shower, put bike away, whatever.)
Fueling appropriately and then ceasing it rapidly is a great way to get blood sugar crash. You should still fuel appropriately. Glad that you are!