Originally Posted by waterrockets

Sometimes I'll do a block of two sets/week. Most of the time I get two threshold workouts unless I'm in base. It is best to toss it up a bit between push and pull threshold workouts. ZCI™s are clearly a pull workout. I've been told by someone much smarter in this than myself, that spending an entire block doing just pull workouts is fine, but don't do two blocks in a row of them.

The push workouts (like 2x20s) should be legitimate push workouts, and it is okay if they don't push you to failure. They are still training the correct zone. Recovery from them is just as important as the much more intense ZCI™ workouts, even though you don't feel as fatigued at the end of them.

Note that sometimes a 2x20 workout can be a pull workout too, since we can go over FTP for that duration repeatably. So, that interval duration can go either way and still be effective. If you prefer harder 2x20s like this, then maybe do a 2x40 or 1x40 or just do a solo SST ride.