I'm not up on how isometric type "interval" work "works", but I think you could do some barbell complexes or similar type conditioning work as long as it's intelligently programmed. Zourdos et al. is actually studying muscle retention and strength changes in 2 conditioning cohorts right now. 1 cohort is doing traditional HIIT on a Wingate bike, as I recall, and the other cohort is lifting weights quickly- the competition lifts (SQ/BP/DL) or some permutation of those. Again, this is all pre-published data so I do not know the accuracy of my report just yet. At any rate, preliminary data shows potentially good things for barbell type circuits when work is equivalent between them and the HIIT group.