The iliacus is best trained with straight legged sit-ups, something the old timers did on a frequent basis.
I have done them, as well as stretched and foam rollered on the regular (piriformis issues), and my back issues have been minimal, despite training consistently for 17 years, training heavy, playing Division I tennis, now playing golf, etc.
I think the iliacus is far too neglected.
Further, I think we have overcomplicated training (even for bodybuilding--I am not referring to competitive bodybuilding where massive drugs are required). A simple routine that consists of compound movements (squats, chins, dips, rows, incline press-I hate the flat bench, overhead work) mixed with some tried and true single joint-esque movements (sldl, hypers, calf work--far too neglected, bis, tris), and you have a very good routine.
