A lot of times, IM run pace is an awkward pace for a lot of athletes, so I think that a good bit of training at that particular pace with whatever method you are going to use to get through the marathon is a good thing. If you are going to run 8 minutes, walk 1, then practice it.
if the purpose of training is to get faster, and not rehearse going slow, why prescribe this?
or, on the flip, if your IM run is 4hrs after 7 hours of swimming and biking, why not train it that way?
+1. My longer runs tend to be close to this pace, but for me, my current IM pace actually falls at the top end of zone 1, following Friel HR zones… though that’s before HR creep sets in, so I’ll probably be in zone 2, 6 hours into the race.
My longer runs end up being just slightly faster or right at IM pace. I try and vary the efforts slightly between zone 1 & 2 by running a little harder uphill. All my running routes have rolling to steeper short hills.