Isn't muscular endurance simply having enough strength reserves to deal with the load? In other words, if your goal is to be able to do 20 reps at X load, wouldn't an increase of strength so you can do 10 reps at twice X load give you the muscular endurance to do 20 reps?
I realize muscular endurance also has to do with lactic thresholds, energy systems, and that sort of thing. But is there actually a meaningful difference between muscular endurance and strength? If you get stronger don't you automatically have better muscular endurance?
What am I missing?