OK, so I plan to give racing a try next year, so I'm looking at Friel's book the Cyclist Training Bible. There is something that does not make sense to me. In Chapter 6, he introduces the triangle with corners defined by Force, Endurance, and Speed Skills. He then goes on to define Muscular Endurance as the combination of Force and Endurance. OK, I have no problem with that part. Now, if you asked me, I would say that the combination of Endurance and Speed Skill is the ability to maintain a high cadence for a long time, NOT necessarily with a lot of Force. But Friel indicates that the combination of these two is "the ability to resist fatigue at high cadence while turning a big gear." But this to me is the combination of all three corners - Force, Endurance, and Speed - i.e., the ability to apply a lot of force (i.e., big gear), at a fast cadence, for a long time. In point of fact, I think schematically there should be something in the CENTER of the triangle which is the combination of all three. So you start out working on Force, Endurance, and Speed Skill separately, then work on the pairwise combinations, then work on the combination of all three.

Hopefully you guys can straighten me out on this, otherwise I won't get to the next chapter!

From what I remember, the combo of endurance and speed skills is anaerobic endurance, meaning the ability to go really fast, hammering your heart rate for longish periods of time (3-10min). The big gear part I think is just added in to show the extra effort, and thus extra speed you would be putting out under such efforts.

Each of these factors trades off against the other. There are no sharp "cliffs" between endurance and speed, for example, but we all know that the slower we go, the longer we can go. You're over-analyzing. Just accept his proposed mental model, and move on. The specific workouts will get you to your limit in combining these things in a good balance.