@Manny,
Just like power has a different meaning depending on the duration of time we’re talking about, strength is the same way. The Sufferfest strength training program is meant to improve functional strength; the kind of strength that makes you more durable and stronger, both in cycling and your daily life. If you want to get stronger in terms of max strength, then yes, you must lift weights. There are many ways to program strength, and you could lift weights to become a stronger cyclist, but you might also miss a lot of the smaller muscles that a lot of lifters fail to recognize that are important to cycling (and every day life), like core, stability, balance, etc. There is a bit of a cardiovascular component to our program as well, mostly because you’re not loading with any significant weight, so in order to increase difficulty, we have to extend the time you’re performing the exercise. The benefit of this, however, is that it will improve your strength as a cyclist on hills, especially long ones!