Maybe there's a very telling reason why connective tissue, fascia, etc. keep getting mentioned as parts to condition, along with breath, etc. . . and the answers you've been given should be enough to get you started looking in the right direction.
I think there's more meat in discussions of "how" you condition the connective tissue -- which have already been touched on somewhat with talk of "held tensions", "postures", "stretching" in conjunction with breathwork . . in addition to the importance of not using local muscles . . so if you aren't using local muscle then how are you moving? Ki/Qi? How are you manifesting that, then?
So far the only reason I can be certain of the role of connective tissues is the 'muscle/tendon changing classic' aka Yi Jin Jing and that tendon does not mean just tendons but generically connective tissues being generally considered a primary source for the whole IT business. That is why it keeps getting mentioned - becasue it is brought up in Yi Jin Jing ... the classic appeal to authority!
I'm looking for more reasons that can be supported by technical, scientific and medical means because that is the way I roll. As some consider this type of thinking a diversion or a distraction I apologize for the thread hijack. I've made my piece as clear as I'm able and I'll not disturb this thread anymore.