I understand that limits of endurance are:
- limited amount of lactate one can reabsorb
- limited amount of carbs one can "refill"

Assuming I cycle slow enough that I will never create more lactate than I reabsorb and burn less carbs than I refill, those would not be limiting factors.

If one looks at athletes in ultra endurance races, like race across America, the main limit seems to be sleep.

When I read training plans, they often seem to be optimized to increase vo2max, Lactate Resorption or fat burning. 

**Question:**

Which training unit / signal cascade optimally improves how long I can ride before getting to fatigue? 


**What I tried / assume?**

I would assume that I can improve the endurance by taking long rides. But I don't really understand what I actually improve (muscle fatigue but how?). Also, which length and frequency of training units would be most effective? (E.g. Taking one ride of 100% of my maximal capacity or five rides with e.g. 80% of my maximal capacity).