I do weighted stretches. I think it helps break the fascia casings up around the muscle tissue. I don't go that heavy. I do 30 second stretches using 40 ibs dumbells for flyes and do 30 sfor triceps, just stretching behind my head like a regular tricep stretch but holding a dumbell for extra resistance. Liek to hang a 50 ibs dumbell from a belt and stretch my lats on a chinning bar, etc. I know the guys who use DC training do this sort of thing. I'm not convinced of its benefits, but it seems very plausable that it could be beneficial and I considering weighted stretches to be one of those things that probably will not impede progess, but may help.