Hopefully I word this so it makes sense. Heading towards Ironman Lake Tahoe next September, wont race a tri till a HIM next July. I have a 50 mile ultra December 1st.
Currently I'm at 72 mile run weeks, first off because I have time plus my body handles this load just fine. I'm curious what impacts others who have done an Ironman then an ultra then an IM as far as run performance at the IM after the ultra vs the IM run prior to the ultra. I 'am' noticing I am developing much more patience than I used to have and simply enjoying the process.
well I will comment even though I can't answer your question because I think your question is important and deserves much discussion.
The answer will depend on how you are running those 72 miles and how much you usually ran, I think. I can't see your logs but if you following a barryP method with maybe some 2 a days on road racing type surfaces and terrain and are running more than you used to then I imagine your stand alone run performance would be better. But, if you are not riding then your loss in bike fitness may reduce any gains in the marathon of an IM.
If your training plan involves running up and down mountains for 4 to 5 hours at a time then I think your stand alone marathon would suffer as would your IM marathon....unless your marathon was Pikes Peak.
Of course this is assuming that you are at some sort of peak physical condition prior to your initial IM and ultra training. If your ultra training actually makes you fitter then you have the added variable of how general fitness would effect your marathon or IM marathon time.
I think the key would be to not try to lose too much bike fitness while you train for your ultra. I would think that if you could retain a good portion of your bike performance while increasing your run volume then when you return to IM training you will start at a better starting point than you did for your pre ultra IM.
But you probably know all this and were just looking for a real live person who has been through what you are doing.
I've never run an ultra, but I can add this to the discussion.
Last summer I ran a lot -- peaking at 100mpw for a few weeks. This was prior to Long Course Worlds (not in preparation, just prior -- I was running a lot just because I wanted to). It had two related effects on my performance (such as it was) at worlds. First, my bike ride there was awful. I just couldn't ride enough to prepare, given all the running. I knew this going in and so I'm fine with it. Second, the awful bike led to what probably, without the running, would have been a DNF on the run, but the big run volume (big for me, relative to anything I had done before) got me through the run, and in fact I actually placed higher in the run relative to the field than I did in the bike, though still underperformed relative to my ability (because I was wiped out from the bike).
I think that if you have enough time to regain bike fitness after the higher mileage running, then the overall effect of a block of high-volume running would be beneficial. (There might be better ways to improve triathlon performance, but the overall effect would not be negative, IMO, if you leave yourself enough time to build the necessary bike fitness. I didn't.)