Google “Carbohydrate Periodization” or James Morton and “Fuel for the Work Required”.
Morton is a sports nutritionist, academic researcher, and also works at Sky.
One thing that really stood out to me is that he studied carb loaded workouts and saw no post workout muscle adaptations.
There are various scenarios - carb up to the max for a race or hard intervals. Train low. Another is Train normal and then sleep low. By ‘low’ I mean low carbohydrate. Another is sleep low and then train low the next morning.
These are not fasted or keto workouts. The point is that they see greater adaptations working in depleted states. I think this is a next level thing. It may be a marginal gain but if you are already mid or high volume and been training for a few years you are probably ready for marginal gains as you’ve grabbed all the low hanging fruit. I also think this is one reason why ‘the long ride’ is beneficial. Towards the end you will be carbohydrate depleted unless you constantly sucked down gels for 4 hours.
Remember the goal is not to crush the workout but for the workout to generated stress which in turn generates adaptations. Fuel for and crush the race or Saturday group ride.