boring, but more like the real thing
If it's boring, it's probably not going to work. You need to be motivated and keen to climb well, whether it's training or climbing outdoors. All this stuff about varying intensity is all very well, but if you don't push yourself you aren't going to get any stronger. And if you don't enjoy yourself you aren't really going to push yourself.
I can only speak from my own experience - and I'm sure others will know more than me - but when I climb inside I set myself problems that I really want to climb. Usually they start off being too hard for me. So I find other problems with easier moves, but keep coming back to my projects. After about 3 or four weeks weeks I can usually climb whatever it was that when I first set it I found impossible. That tells me I've got stronger.
Having said all that, I did develop a tendon injury which I'm suffering from right now. All that time indoors and now that I finally move somwhere with real rock I can't climb. Ah well. But I think if you make sure you warm down and stretch sensibly after every session, pushing yourself indoors shouldn't lead to injuries or being tight. I found it really made a difference if I spent 20min. at the end of a session doing easy problems and traverses - loosened me up loads.
So there's my tuppence worth.
