hey CB32, first of all, thanks for your post. Second, when you say major, what is the distance you are talking about. There are many distances which people seems to all think are major, so more info will help - spr, oly, halfs or IM?

to answer your question, you do both. Brick workouts are good, but those generally tend to be shorter in duration and more focused on using your muscle groups one after another. long rides or long runs are important as well, as they teach you about techniques.

let me know more info and I can go from there.