Re: theory on cardio endurance & muscular endurance
Yes, that's pretty much true. Strength increases the capacity for endurance.
Who's more likely to win a "lift this heavy object over your head as many times as possible in 40 minutes" competition: a guy who is ridiculously strong overhead, or a guy who has good arm endurance (whatever what means). It's going to be the first guy. He is stronger, therefore he fatigues slower at heavy weights, and therefore higher total output.